concanavalin-a and Chagas-Disease

Chagas disease is a neglected tropical disease. The ability of Trypanosoma cruzi to survive within phagocytes is likely a critical factor for T. cruzi dissemination in the host. For control of the parasite load and host survival, macrophage action is required. Concanavalin-A (Con-A) presents properties that modulate immune functions and protect hosts from several experimental infectious diseases. Here, we evaluated the effects of Con-A on peritoneal macrophages as well as on the course of experimental infection by T. cruzi.. BALB/c mice, a susceptible model for T. cruzi infection, were treated with Con-A via the intraperitoneal route and 3 days later infected with T. cruzi. We quantified parasitemia, cytokines and nitric oxide (NO). Peritoneal exudate and macrophages were collected for macrophage phenotyping and cell viability, NO and cytokine detection, as well as for T. cruzi internalization and release index determination.. Con-A treatment induced IL-17a and NO production by cells from the peritoneal cavity, and M1 marker expression predominated on peritoneal macrophages. These cells are also more prone to producing TNF-α, IL-6 and NO when infected by T. cruzi and show high trypanocidal capacity. Due to a hostile peritoneal microenvironment caused by Con-A, which induces macrophage cNOS and iNOS expression, infected BALB/c mice showed reduced parasitemia and an increased survival rate.. We conclude that Con-A can induce peritoneal M1 macrophage polarization to increase trypanocidal activity, resulting in ameliorated systemic infection in a susceptible experimental model.

Topics: Animals; Cell Polarity; Chagas Disease; Concanavalin A; Female; Interleukin-17; Macrophages, Peritoneal; Mice, Inbred BALB C; Nitric Oxide; Nitric Oxide Synthase Type II; Parasitemia; Trypanosoma cruzi

During the course of infection by Trypanosoma cruzi, the host immune system is involved in distinct, complex interactions with the endocrine system, and prolactin (PRL) is one of several hormones involved in immunoregulation. Although intensive studies attempting to understand the mechanisms that underlie Chagas' disease have been undertaken, there are still some pieces missing from this complex puzzle. Because data are scarce concerning the role of PRL involvement in Chagas' disease and taking into account the existence of crosstalk between neuroendocrine hormones and the immune system, the current study evaluates a possible up-regulation of the cellular immune response triggered by PRL in T. cruzi-infected rats and the role of PRL in reversing immunosuppression caused by the parasitic infection. The data shown herein demonstrate that PRL induces the proliferation of T lymphocytes, coupled with an activation of macrophages and the production of nitric oxide (NO), leading to a reduction in the number of blood trypomastigotes during the peak of parasitemia. During the acute phase of T. cruzi infection, an enhancement of both CD3+CD4+ and CD3+CD8+ T cell populations were observed in infected groups, with the highest numbers of these T cell subsets found in the infected group treated with PRL. Because NO is a signaling molecule involved in a number of cellular interactions with components of the immune system and the neuroendocrine system, PRL can be considered an alternative hormone able to up-regulate the host's immune system, consequently lowering the pathological effects of a T. cruzi infection.

Topics: Animals; Cell Proliferation; Chagas Disease; Concanavalin A; Flow Cytometry; Immunity, Innate; Lipopolysaccharides; Macrophages, Peritoneal; Male; Nitric Oxide; Parasitemia; Prolactin; Rats; Rats, Wistar; T-Lymphocyte Subsets; Thymocytes; Trypanosoma cruzi; Up-Regulation

Melatonin by exhibiting antioxidant, anti-aging, and immunomodulatory properties favorably modulate the immune function, protecting the hosts from several infectious diseases. Zinc is an essential trace element important for the efficiency of the immune system in reason of its widespread role in the activity of enzymes, transcription factors and cytokines. The etiology of Chagas' disease, caused by a protozoan parasite Trypanosoma cruzi, has been the focus of considerable discussion, although chronic phase still remains not fully understood. This study showed that zinc and melatonin treatment did not affect the percentage of both CD4+ and CD8+ T lymphocytes subsets in chronically infected animals. Increased levels of IL-2 and IL-10, as well as, enhanced thymocyte proliferation in T. cruzi infected groups under zinc and melatonin therapy was observed as compared to untreated group. Conversely, during the chronic phase of infection, macrophages counts were reduced in melatonin and zinc-melatonin treated animals. The combined actions of zinc and melatonin have beneficial effects in counteracting parasite-induced immune dysregulation, protecting animals against the harmful actions of chronic T. cruzi infection. Furthermore, our results provide an experimental basis for further studies on the role of immunomodulatory therapies.

Topics: Animals; Antigens, CD; Cell Count; Cell Proliferation; Chagas Disease; Chronic Disease; Concanavalin A; Cytokines; Interleukin-10; Interleukin-2; Macrophages, Peritoneal; Male; Melatonin; Parasitemia; Phenotype; Rats; Rats, Wistar; Thymocytes; Trypanosoma cruzi; Zinc

Control of the acute phase of Trypanosoma cruzi infection is critically dependent on cytokine-mediated macrophage activation to intracellular killing, natural killer (NK) cells, CD4(+) T cells, CD8(+) T cells and B cells. Cell-mediated immunity in T. cruzi infection is also modulated by cytokines, but in addition to parasite-specific responses, autoimmunity can be also triggered. Importantly, cytokines may also play a role in the cell-mediated immunity of infected subjects. Here we studied the role of cytokines in the regulation of innate and adaptive immunity during the acute phase of T. cruzi infection in Wistar rats. Melatonin is an effective regulator of the immune system. Macrophages and T lymphocytes, which have melatonin receptors, are target cells for the immunomodulatory function of melatonin. In this paper melatonin was orally given via two protocols: prior to and concomitant with infection. Both treatments were highly effective against T. cruzi with enhanced action for the concomitant treatment. The data suggest an up-regulation of the TH-1 immune response as all analyzed parameters, interleukin (IL)-4, IL-10, transforming growth factor-beta1 and splenocyte proliferation, displayed reduced levels as compared with the untreated counterparts. However, the direct effects of melatonin on immune cells have not been fully investigated during T. cruzi infection. We conclude that in light of the current results, melatonin exerted important therapeutic benefits through its immune regulatory effects.

Topics: Analysis of Variance; Animals; Chagas Disease; Concanavalin A; Cytokines; Immunity, Active; Immunity, Innate; Interleukin-10; Interleukin-4; Macrophages; Melatonin; Parasitemia; Rats; Rats, Wistar; Th1 Cells; Th2 Cells; Transforming Growth Factor beta; Trypanosoma cruzi

We investigated the possible role of prostaglandins produced by COX-2 in the immunosuppression observed during Trypanosoma cruzi infection. Con-A-stimulated splenocytes isolated from mice on days 5, 10, and 15 of infection released large amounts of PGE2 and this release was inhibited by the treatment of animals with sodium salicylate or meloxicam. The treatment of the animals with these drugs enhanced the release of IL-2 by splenocytes from T. cruzi-infected animals and significantly reduced the blood parasitemia and delayed the mortality of the infected mice. Furthermore, the release of TNF-alpha, IFN-gamma, IL-4, and IL-10 by Con-A-stimulated splenocytes obtained from infected mice on days 5, 10, and 15 of the infection was significantly inhibited by treatment of the animals with salicylate or meloxicam. In conclusion, the results suggest that the prostaglandins produced mainly by COX-2 mediate the immunosuppression observed in the acute phase of T. cruzi infection.

Topics: Acute Disease; Animals; Cells, Cultured; Chagas Disease; Concanavalin A; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; Cytokines; Dinoprostone; Immune Tolerance; Lymphocyte Activation; Male; Meloxicam; Mice; Mice, Inbred BALB C; Parasitemia; Prostaglandin-Endoperoxide Synthases; Sodium Salicylate; Spleen; T-Lymphocytes; Thiazines; Thiazoles

Trypanosoma cruzi, the causative agent of Chagas' disease, induces transient thymic aplasia early after infection-a phenomenon that still lacks a molecular explanation. The parasite sheds an enzyme known as trans-sialidase (TS), which is able to direct transfer-sialyl residues among macromolecules. Because cell-surface sialylation is known to play a central role in the immune system, we tested whether the bloodstream-borne TS is responsible for the thymic alterations recorded during infection. We found that recombinant TS administered to naive mice was able to induce cell-count reduction mediated by apoptosis, mimicking cell subsets distribution and histologic findings observed during the acute phase of the infection. Thymocytes taken after TS treatment showed low response to Con A, although full ability to respond to IL-2 or IL-2 plus Con A was conserved, which resembles findings from infected animals. Alterations were found to revert several days after TS treatment. The administration of TS-neutralizing Abs to T. cruzi-infected mice prevented thymus alterations. Results indicate that the primary target for the TS-induced apoptosis is the so-called "nurse cell complex". Therefore, we report here supporting evidence that TS is the virulence factor from T. cruzi responsible for the thymic alterations via apoptosis induction on the nurse cell complex, and that TS-neutralizing Abs elicitation during infection is associated with the reversion to thymic normal parameters.

Topics: Acute Disease; Animals; Antibodies, Protozoan; Apoptosis; Cell Count; Cell Division; Chagas Disease; Concanavalin A; Glycoproteins; Interleukin-2; Male; Mice; Neuraminidase; Neutralization Tests; Thymus Gland; Trypanosoma cruzi; Virulence

Polyclonal lymphocyte activation and hypergammaglobulinemia characterize the acute phase of Chagas' disease, a debilitating condition caused by Trypanosoma cruzi. Such pathogenic hyper-reactivities not only compromise specific host defense against the pathogen, but may also contribute to infection-induced chronic autoimmune responses. Recent studies showed that T. cruzi trans-sialidase (TS) directly stimulates the polyclonal proliferation and Ig secretion of normal murine B cells in a T-independent, Bruton's tyrosine kinase (Btk)-dependent manner. Related to this observation, we now show that parasite-derived and recombinant TS potentiate the proliferation and cytokine secretion of normal T cells triggered by antigen-specific and non-specific stimuli. TS potentiates T cell activation through stimulating B cells and macrophages, independent of CD40/CD40L and CD43 pathways. In contrast, optimal TS potentiation requires interleukin-6 (IL-6) and Btk, as it is significantly reduced in splenocytes from IL-6-/- and Btk-defective Xid mice. The results suggest that TS, directly and indirectly, activates both antigen-presenting cell and T cell compartments, and that TS-induced IL-6 may further amplify such activation. These observations open up the possibility that TS drives the polyclonal lymphocyte activation in acute T. cruzi infection, a phenomenon contributing to the pathogenesis of Chagas' disease.

Topics: Agammaglobulinaemia Tyrosine Kinase; Animals; Antigen-Presenting Cells; Antigens; Antigens, CD; B-Lymphocytes; CD40 Ligand; Cell Division; Cells, Cultured; Chagas Disease; Coculture Techniques; Concanavalin A; Cytokines; Gene Deletion; Glycoproteins; Immunologic Memory; Interleukin-6; Leukosialin; Lymphocyte Activation; Macrophages; Mice; Mice, Inbred Strains; Neuraminidase; Protein-Tyrosine Kinases; Sialoglycoproteins; Signal Transduction; Spleen; T-Lymphocytes; Trypanosoma cruzi

Gamma-interferon (IFN-gamma) production, the hallmark of the Th1 immune response, has been shown to play a central role in the resistance to Trypanosoma cruzi infections, in particular when produced in the very early acute infection. BALB/c mice infected with T. cruzi, Tulahuén strain, reach high parasitemias during the acute phase, and their spleen cells release IFN-gamma in the second week of the infection, while those of the resistant C3H strain produce the cytokine earlier, at 2 days post-infection (pi). We studied in the spleen cells supernatants of infected BALB/c and C3H mice, the spontaneous production of cytokines involved in the induction, interleukin (IL)-18 and IL-12 p70, as well as in the downregulation, IL-13 and IL-10, of the Th1 immune response. We found that, at 2 days pi, only C3H mice produced IL-18, while IL-12 p70 was detected in both mouse strains. Moreover, at this time pi splenocytes from BALB/c mice spontaneously produced high amounts of IL-13. At 14 days pi, despite the increased levels of IL-13 and IL-10 detected in C3H mice, they still showed high concentrations of IL-18 and IL-12 p70. In contrast, spleen cells from BALB/c mice did not secrete IL-18, IL-12 p70 and IL-13 at this time pi, but produced higher amounts of IL-10 than C3H mice. Non of these cytokines was found increased in the cell supernatants of chronically infected mice. The addition of lipopolysaccharide (LPS) or Concanavalin A (Con A) to the cell cultures did not enhance the production of IL-18 and IL-12 at the time points tested. On the other hand, at 21 days pi, when parasitemia peaked, an inhibition of both the LPS induced IL-10 release and the IL-13 production upon Con A stimulation was observed in C3H, but not in BALB/c mice. We did not find an increase of IL-18, IL-10, or IL-12 p70 in the serum of the infected mice, despite the high seric IL-12 p40 concentrations reached during the infection. The data show that the different kinetics of the production of these cytokines in the spleen of both mouse strains could have a key role in the in vivo regulation of IFN-gamma production. In these experimental models, early IFN-gamma release and thus resistance to T. cruzi infection, could be related to the combined effect of both IL-18 and IL-12p70 in the absence of IL-13.

Topics: Acute Disease; Animals; Chagas Disease; Concanavalin A; Disease Models, Animal; Interferon-gamma; Interleukin-10; Interleukin-12; Interleukin-13; Interleukin-18; Lipopolysaccharides; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Spleen; Th1 Cells; Time Factors; Trypanosoma cruzi

The cytokine interleukin-12 (IL-12) is essential for resistance to Trypanosoma cruzi infection because it stimulates the synthesis of interferon-gamma (IFN-gamma), a major activator of the parasiticidal effect of macrophages. A less studied property of IL-12 is its ability to amplify the proliferation of T or natural killer (NK) lymphocytes. We investigated the role of endogenously produced IL-12 in the maintenance of parasite antigen (T-Ag)-specific lymphoproliferative responses during the acute phase of T. cruzi infection. We also studied whether treatment with recombinant IL-12 (rIL-12) would stimulate T-Ag-specific or concanavalin A (Con A)-stimulated lymphoproliferation and abrogate the suppression that is characteristic of the acute phase of infection. Production of IL-12 by spleen-cell cultures during T. cruzi infection increased in the first days of infection (days 3-5) and decreased as infection progressed beyond day 7. The growth-promoting activity of endogenous IL-12 on T-Ag-specific proliferation was observed on day 5 of infection. Treatment of cultures with rIL-12 promoted a significant increase in Con A-stimulated proliferation by spleen cells from normal or infected mice. Enhanced T-Ag-specific proliferation by rIL-12 was seen in spleen cell cultures from infected mice providing that nitric oxide production was inhibited by treatment with the competitive inhibitor NG-monomethyl-L-arginine (NMMA). Enhancement of proliferation promoted by IL-12 occurred in the presence of neutralizing anti-interleukin-2 (IL-2) antibody, suggesting that this activity of IL-12 was partly independent of endogenous IL-2. Thymidine incorporation levels achieved with rIL-12 treatment of the cultures were approximately 50% of those stimulated by rIL-2 in the same cultures.

Topics: Acute Disease; Animals; Antibodies, Monoclonal; Antigens, Protozoan; Cell Culture Techniques; Cell Division; Chagas Disease; Concanavalin A; Dose-Response Relationship, Immunologic; Female; Interleukin-12; Interleukin-2; Lymphocyte Activation; Mice; Mice, Inbred C57BL; Recombinant Proteins; T-Lymphocytes; Trypanosoma cruzi

CBA/J mice can be protected against lethal infection with Trypanosoma cruzi by treatment using T. cruzi soluble extract antigen (TCSE). In vivo administration of TCSE (400 microg/mouse) into naive mice increased the cellular proliferative response to Con A and elevated the levels of IFN-gamma. The production of IFN-gamma was extremely important in controlling the replication of the parasite since the protective activity of TCSE was completely abrogated by in vivo treatment with an anti IFN-gamma neutralizing antibody. These results suggest that depending on the level, cytokine production results in the control of replication of the parasite in experimental Chagas' disease.

Topics: Animals; Antibodies, Blocking; Antigens, Protozoan; Cell-Free System; Chagas Disease; Concanavalin A; Dose-Response Relationship, Immunologic; Female; Interferon-gamma; Lymphocyte Activation; Mice; Mice, Inbred CBA; Protozoan Vaccines; Solubility; Spleen; Trypanosoma cruzi

Trypanosoma cruzi (Y strain)-infected interleukin-4(-/-) (IL-4(-/-)) mice of strains 129/J, BALB/c, and C57BL/6 showed no significant difference in parasitemia levels or end point mortality rates compared to wild-type (WT) mice. Higher production of gamma interferon (IFN-gamma) by parasite antigen (Ag)-stimulated splenocytes was observed only for C57BL/6 IL-4(-/-) mice. Treatment of 129/J WT mice with recombinant IL-4 (rIL-4), rIL-10, anti-IL-4, and/or anti-IL-10 monoclonal antibodies (MAbs) did not modify parasitism. However, WT mice treated with rIL-4 and rIL-10 had markedly increased parasitism and suppressed IFN-gamma synthesis by spleen cells stimulated with parasite Ag, concanavalin A, or anti-CD3. Addition of anti-IL-4 MAbs to splenocyte cultures from infected WT 129/J, BALB/c, or C57BL/6 mice failed to modify IFN-gamma synthesis levels; in contrast, IL-10 neutralization increased IFN-gamma production and addition of rIL-4 and/or rIL-10 diminished IFN-gamma synthesis. We conclude that endogenous IL-4 is not a major determinant of susceptibility to Y strain T. cruzi infection but that IL-4 can, in association with IL-10, modulate IFN-gamma production and resistance.

Topics: Animals; Cells, Cultured; Chagas Disease; Concanavalin A; Cytokines; Female; Interferon-gamma; Interleukin-10; Interleukin-4; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Recombinant Proteins; Spleen; Time Factors; Trypanosoma cruzi

Helminth infections are frequently massive, chronic and strong inductors of Th2-type cytokines. This implies that infection by such parasites could alter the susceptibility to subsequent infections by other pathogens, particularly intracellular parasites. We therefore explored whether a persistent infection, caused by Taenia crassiceps cysticerci, in BALB/c mice could affect susceptibility to a later infection by Trypanosoma cruzi. We found that the presence of the cysticerci indeed modified the immune response and the susceptibility to T. cruzi, and that these modifications depended on the time-course evolution of the initial infection. Coinfection with the protozoan in the early stages of the helminth infection, induced a delay on the onset of parasitaemia, early specific production of IFN-gamma and high specific production of IL-4. A significant increase in susceptibility to T. cruzi was observed only when mice were coinfected in late stages when the helminth load is greater and a Th2 type response against it is predominant. The in vitro specific response to T. cruzi antigens was then characterized by low levels of both IFN-gamma and IL-4. These findings suggest that chronic helminth infections could potentially have a significant influence over the immune response and hence susceptibility to other pathogens.

Topics: Animals; Antibody Specificity; Antigens, Helminth; Chagas Disease; Concanavalin A; Cysticercosis; Cytokines; Female; Lymphocyte Activation; Lymphocytes; Mice; Mice, Inbred BALB C; Parasitemia; Spleen

Here we demonstrate that T. cruzi antigen molecule SAPA (shed acute phase antigen) with neuraminidase-trans sialidase activity triggers down-regulation of T lymphocyte proliferation by interacting with T lymphocyte muscarinic acetylcholine receptors (mAChR). SAPA attachment to mAChR from Lyt 2.2+ T cells resulted in synthesis of cyclic GMP (cGMP) and secretion of PGE2, an immunoregulator effector substance. These T suppressor cell signals were blunted by atropine and by indomethacin. Cell sorter analysis showed that the interaction of SAPA with purified T cells, affected the ratio of L3T4+/Lyt 2.2+ T cells increasing the percentage of Lyt 2.2+ T cells, effect that was inhibited by the mAChR antagonist, atropine. The interaction between SAPA and mAChR from Lyt 2.2+ T cells may result, therefore, in the down-regulation of the host immune response as consequence of T suppressor/cytotoxic cells activation and PGE2 release as they were observed. These results support the theory of an immunosuppressive state that contribute to the chronic course of Chagas' disease.

Topics: Animals; Antigens, Protozoan; Atropine; Cell Division; Chagas Disease; Chronic Disease; Concanavalin A; Cyclic GMP; Cyclooxygenase Inhibitors; Dinoprostone; Down-Regulation; Indomethacin; Mice; Mice, Inbred BALB C; Muscarinic Antagonists; Receptors, Muscarinic; T-Lymphocytes; Trypanosoma cruzi

A possible role for tumor necrosis factor (TNF) alpha during Trypanosoma cruzi infection was explored by using transgenic mice expressing in blood high levels of a soluble TNFR1-FcIgG3 fusion protein, which neutralizes the effects of TNF in vivo. Nontransgenic littermates were used as controls. The transgenic mice showed high susceptibility to T. cruzi infection. Inocula sublethal for control mice resulted in over 80% mortality associated with higher levels of parasites in the blood. In histological sections of the hearts of transgenic mice, large parasitic clusters without inflammatory cell infiltrates around the parasites were seen, while smaller parasitic clusters associated with leukocytes were seen in control mice. No difference in specific antibody response or lymphocyte composition of the spleen was found between transgenic and control mice, although the unresponsiveness of spleen cells to concanavalin A stimulation in vitro, typical of the acute phase of T. cruzi infection, was less pronounced in transgenic mice. Infected transgenic mice produced higher levels of gamma interferon than did control mice. These results confirm that TNF is involved in mechanisms leading to parasite clearance and protection from death in the acute phase of T. cruzi infection. More importantly, the data reveal that TNF is necessary for the establishment of effective tissue inflammation and parasite load control in acute experimental Chagas' disease myocarditis.

Topics: Acute-Phase Reaction; Animals; Chagas Disease; Concanavalin A; Disease Susceptibility; Inflammation; Interferon-gamma; Lymphocyte Activation; Lymphocyte Subsets; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; Mice, Transgenic; Spleen; Trypanosoma cruzi; Tumor Necrosis Factor-alpha

The cardiac pathology associated with infection by Trypanosoma cruzi in mice has been suggested to be partially dependent upon cytokine responses. The pathoresistant B10.D2 mice, which display little infection-induced myocarditis, and the pathopermissive DBA/2 mice, which show significant cardiac damage, were compared for their in vitro interferon (IFN)-gamma and interleukin (IL)-4 production. Concanavalin A-stimulated spleen cells from infected B10.D2 mice produce a greater amount of IFN-gamma than DBA/2 mice, whereas the IL-4 production is only slightly greater in the B10.D2 mice than the DBA/2 mice. Parasite antigen stimulation of spleen cells from these mice results in a clearly greater IFN gamma production by the B10.D2 and a higher IL-4 level for the DBA/2 mice. The data presented suggest a relationship between an enhanced TH1-type response and decreased chronic cardiac pathogenesis, whereas a lower level of TH1 activity may play a role in cardiac involvement.

Topics: Animals; Antigens, Protozoan; Cells, Cultured; Chagas Cardiomyopathy; Chagas Disease; Concanavalin A; Disease Susceptibility; Immunity, Innate; Interferon-gamma; Interleukin-4; Mice; Mice, Inbred DBA; Mice, Inbred Strains; Parasitemia; Spleen; Th1 Cells; Th2 Cells; Trypanosoma cruzi

Survival of acute Trypanosoma cruzi infection by mice is influenced by genes inside and outside the major histocompatibility complex (MHC) and genes associated with resistance must be expressed in both the MHC and the genetic background or the host will die within a few weeks of infection. Both the levels and the kinetics of cytokine production have also been implicated as important factors for resistance. Antigen-stimulated spleen cells from mice that express the resistant H-2q MHC haplotype produced significantly more interferon (IFN)-gamma than did cells from mice that share the susceptible H-2k haplotype. But, spleen cells from susceptible and resistant mice produce similar levels of IFN-gamma when stimulated with concanavalin A. The kinetics of interleukin (IL)- 10 production by ConA (ConA)-stimulated spleen cell were inversely correlated with IFN-gamma levels throughout the course of acute infection in all mouse strains. Levels of IL-2 produced by ConA-stimulated spleen cells were also initially high (day 0) then decreased as acute infection progressed. Conversely, IL-4 production by ConA-stimulated spleen cells increased during infection, and mice that express the susceptible C3H background produced significantly more IL-4 than those that share the resistant B10 background. IL-2 production by lymph node cells from mice that express the susceptible C3H genetic background also declined during infection, while lymph node cells from B10 background mice showed a moderate increase in IL-2 secretion. These data suggest that both the levels and the kinetics of cytokine production may be genetically regulated and that cytokine responses are compartmentalized in the T. cruzi-infected host.

Topics: Animals; Cells, Cultured; Chagas Disease; Concanavalin A; Disease Susceptibility; Enzyme-Linked Immunosorbent Assay; Hybridomas; Immunity, Innate; Interferon-gamma; Interleukin-10; Interleukin-2; Interleukin-4; Interleukin-5; Interleukins; Kinetics; Lymph Nodes; Mice; Mice, Inbred C3H; Spleen

Spleen and lymph node cells of Trypanosoma cruzi-infected mice were studied for mitogen-induced responsiveness in terms of proliferation and lymphokine production (IL-2, IFN-gamma). Splenocyte (SP) as well as lymph node cell (LN) proliferation and IL-2 production were depressed during the acute phase of the infection. Proliferative capacity of LN cells recovered completely and that of SP partially during the chronic phase. In contrast to these suppressive effects, the mitogen-induced IFN-gamma response was enhanced. In vitro co-incubation of normal SP or LN cells with trypomastigotes resulted in a reduced mitogen-induced cell proliferation and IL-2 secretion, similar to those seen with cells taken from infected mice. In contrast, trypomastigotes exerted a stimulatory activity on the mitogen-induced IFN-gamma response of both SP and LN cells. Addition of lymph node cells from T. cruzi-infected mice (LN-I) to lymph node cells of control mice (LN-C) suppressed strongly the mitogen-induced responsiveness of such cocultures. A marginal level of suppression was recorded in cocultures of spleen cells from infected mice (SP-I) and control spleen cells (SP-C). The potent suppressive cells within LN-I populations were identified as macrophage-like and such cells were absent in SP-C and peritoneal exudate cells from T. cruzi infected animals.

Topics: Acute Disease; Animals; Cells, Cultured; Chagas Disease; Concanavalin A; Female; Immune Tolerance; Lymph Nodes; Lymphocyte Activation; Lymphokines; Mice; Mice, Inbred BALB C; Spleen; T-Lymphocytes

Thymocytes from mice with experimental Trypanosoma cruzi infection respond poorly to Con-A stimulation. However, the proliferative capacity of these cells is not impaired, as demonstrated by the fact that at high doses, exogenous rIL-2 restores thymidine uptake. This finding could be explained either by insufficient IL-2 production or by the appearance of inhibitory factors during T. cruzi infection. This paper shows that in response to Con A, IL-2 production is decreased in the model. Furthermore, the whole profile of cytokine production is modified, with a striking increase in IL-10, IFN-gamma, IL-4, IL-5 and IL-6 production. The results indicate that IL-10 plus IFN-gamma are responsible for the decrease in the Con A-induced proliferation since a normal proliferative response as well as normal IL-2 production can be restored if both cytokines are neutralized by adding their monoclonal antibodies (MoAbs). Evidence is provided also for an enhanced non-specific cytotoxicity of thymic cells from infected mice that might involve IL-4, IL-5 and IL-6. This is the first study demonstrating an alteration of thymic cell function by T. cruzi infection which results from overstimulation of IL-10 and IFN-gamma production.

Topics: Animals; Antibodies, Monoclonal; CD3 Complex; Cells, Cultured; Chagas Disease; Concanavalin A; Cytotoxicity, Immunologic; Disease Models, Animal; Interferon-gamma; Interleukin-10; Lymphocyte Activation; Mice; Mice, Inbred C57BL; T-Lymphocytes; T-Lymphocytes, Cytotoxic; Thymus Gland

We have studied the expression of IFN-gamma, IL-2 and IL-2 receptor (IL-2R) at the mRNA and protein levels in spleen and lymph node cells from Trypanosoma cruzi-infected BALB/c mice. At 21 days post infection (dpi) (peak of parasitaemia), spleen cells stimulated with Con A for 16 h showed a reduced IFN-gamma, IL-2 and IL-2R mRNA production compared with non-infected controls. Lymph node cells obtained at 4, 21 or 60 dpi produced similar amounts of IFN-gamma, IL-2 or IL-2R transcripts after mitogen stimulation as uninfected controls. Spleen cells obtained at 21 dpi showed a lower Con A proliferative response and IL-2R expression compared with non-infected controls, while the proliferation and IL-2R expression of lymph node cells at 21 dpi was unaltered. Supernatants from 48 h Con A-stimulated spleen and lymph node cells from mice at 21 dpi had very low levels of IL-2 but contained significantly higher levels of IFN-gamma compared with the supernatants of cells from non-infected mice. The latter phenomenon correlates with an accelerated rate of IFN-gamma mRNA accumulation.

Topics: Animals; Blotting, Northern; Cells, Cultured; Chagas Disease; Concanavalin A; Flow Cytometry; Gene Expression Regulation; Interferon-gamma; Interleukin-2; Lymph Nodes; Lymphocyte Activation; Male; Mice; Mice, Inbred BALB C; Receptors, Interleukin-2; RNA, Messenger; Spleen; Time Factors; Transcription, Genetic

In murine infection with Trypanosoma cruzi, immune responsiveness to parasite and non-parasite Ag becomes suppressed during the acute phase of infection, and this suppression is known to extend to the production of IL-2. To determine whether suppression of lymphokine production was specific for IL-2, or was a generalized phenomenon involving suppressed production of other lymphokines, we have begun an investigation of the ability of mice to produce of a number of lymphokines during infection, initially addressing this question by studying IFN-gamma production. Supernatants from Con A-stimulated spleen cells from infected resistant (C57B1/6) and susceptible (C3H) mice were assayed for IFN-gamma. Supernatants known to be suppressed with respect to IL-2 production from both mouse strains contained IFN-gamma at or above that of supernatants from normal spleen cells. Samples were assayed in an IFN bioassay to ensure that the IFN-gamma detected by ELISA was biologically active. Thus, suppression during T. cruzi infection does not extend to the production of all lymphokines. The stimulation of IFN-gamma production was confirmed by detection of IFN-gamma mRNA in unstimulated spleen cells from infected animals, and in Con A, Con A + PMA, and in some cases, parasite Ag-stimulated spleen cells from infected animals. IFN-gamma mRNA levels in mitogen-stimulated spleen cells equalled or exceeded those found in similarly stimulated normal cells. In contrast, stimulated spleen cells from infected animals had reduced levels of IL-2 mRNA relative to normal spleen cells. Thus at both the protein and mRNA level, IFN-gamma production is stimulated by T. cruzi infection, whereas IL-2 production is suppressed. Serum IFN-gamma in infected C57B1/6 and C3H mice was detected 8 days after infection, peaked on day 20 of infection, and subsequently fell, but remained detectable at low levels throughout the life of infected mice. Infected animals were depleted of cell populations known to be capable of producing IFN-gamma, and Thy-1+, CD4-, CD8-, NK- cells, and to a lesser degree, CD4+ and CD8+ cells were found to be responsible for the production of IFN-gamma during infection. We also report that IL-2 can induce IFN-gamma production in vitro and in vivo by spleen cells from infected animals, and that IL-2 can synergize with epimastigote or trypomastigote antigen to produce high levels of IFN-gamma comparable to those found in supernatants from mitogen-stimulated cells.

Topics: Animals; Antigens, Differentiation, T-Lymphocyte; Antigens, Protozoan; CD8 Antigens; Chagas Disease; Concanavalin A; Female; Interferon-gamma; Interleukin-2; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; RNA, Messenger; Spleen; Tetradecanoylphorbol Acetate

The role of CD8+ T cells in immune control of Trypanosoma cruzi infection in mice was examined by using in vivo depletion of CD8+ T cells with antibodies. Both the resistant C57BL/6J and the highly susceptible C3H/HeSnJ developed higher parasitemias and increased or earlier mortality when depleted of CD8+ T cells before infection with the Brazil strain of T. cruzi. CD8 depletion also affected the induction and expression of immunity to T. cruzi after vaccination with the avirulent Corpus Christi strain of T. cruzi. C57BL/6J mice depleted of CD8+ T cells either before or after vaccination showed a near total loss of vaccine induced protection. C3H mice were only partially protected by the vaccination procedure but the protection was totally reversed by anti-CD8 treatment. Chronically infected mice that had survived the acute infection were unaffected by CD8 depletion and showed neither a recrudescence of parasitemia nor an increased susceptibility to reinfection. These results suggest that CD8+ T cells play a role in immunity to T. cruzi in the acute phase but possibly not during the chronic phase of infection. Also, immunization with Corpus Christi strain T. cruzi induces an immunity that is distinct from that induced by survival of the acute phase of infection. The mechanism by which CD8+ T cells contribute to control of T. cruzi infection is not known. However, CD8 depletion had no effect on suppressed immune responses, suggesting their function in T. cruzi-infected mice is related more to the cytotoxic activity or cytokine-producing capacity of this subpopulation of T cells.

Topics: Animals; Antigens, Differentiation, T-Lymphocyte; CD8 Antigens; Cell Separation; Chagas Disease; Concanavalin A; Immune Tolerance; Lipopolysaccharides; Lymphocyte Activation; Mice; T-Lymphocytes; Trypanosoma cruzi; Vaccination

Release of reactive oxygen species (ROS) by cells from BALB/c mice was studied during the acute stage of the infection with 50 bloodstream forms of Trypanosoma cruzi, Tulahuén strain. Production of ROS by spleen and peritoneal cells was evaluated by chemiluminescence using luminol as enhancer (CL-Lum). Three to four weeks after infection, CL-Lum response after the addition of opsonized zymosan to spleen and peritoneal cells from infected mice was 13 and 98 times, respectively, above the levels obtained with cells from noninfected mice. The kinetics of this hyperactivity was similar to that of the parasitemia. Both reached maximal values on the third to fourth weeks and decreased at 7 weeks postinfection. During this hyperactivation stage, spleen and peritoneal cells from infected mice showed a "spontaneous" CL-Lum response (without any stimulus added in vitro) absent in noninfected mice. Both, "spontaneous" and zymosan stimulated CL-Lum responses were inhibited by 100 microM azide and by 0.8 microM superoxide dismutase, suggesting the involvement of hemoproteins and superoxide anion in the measured responses. Moreover, spleen cells from acutely infected mice displayed a hyperactivity in the CL-Lum response when recombinant interferon-gamma was added in vitro. Supernatants of spleen cells from both normal or infected mice, stimulated in vitro with concanavalin A, contained similar levels of interferon and were equally able to stimulate the trypanocidal activity of normal macrophages. These results suggest that mediators of activation of phagocytic cells can be produced during acute T. cruzi infection. In addition, phagocytic cells from acutely infected mice were activated in vivo and were hyperactive to the in vitro stimulation.

Topics: Acute Disease; Animals; Azides; Chagas Disease; Concanavalin A; Cytotoxicity, Immunologic; Free Radicals; Immunity, Cellular; Interferon-gamma; Luminescent Measurements; Macrophage Activation; Mice; Mice, Inbred BALB C; Oxygen; Peritoneal Cavity; Recombinant Proteins; Spleen; Superoxide Dismutase; Trypanosoma cruzi; Zymosan

A massive activation of T cells takes place during the early stages of a Trypanosoma cruzi infection in mice. We present data indicating that substantial amounts of interleukin 2 (IL-2) are secreted and IL-2 receptors are expressed during the period of increased proliferation (4-7 days post infection). Both concanavalin A-induced proliferation and IL-2 production are markedly decreased later in the acute infection (around 3 weeks post infection). This proliferation cannot be restored by externally added IL-2. Simultaneously, there is a drastic reduction in the number of both high- and low-affinity IL-2 receptors. The reduction is not attributable to the elimination of a particular T-cell population. In vivo administration of recombinant IL-2 failed to improve resistance to T. cruzi parasites as measured by parasitaemia and mortality.

Topics: Animals; Cell Separation; Cells, Cultured; Chagas Disease; Concanavalin A; Flow Cytometry; Interleukin-2; Male; Mice; Mice, Inbred BALB C; Receptors, Interleukin-2; T-Lymphocytes

Mice infected with the protozoan parasite Trypanosoma cruzi, the causative agent of human Chagas' disease, are profoundly immunodepressed in their response to various Ag and mitogens. A key factor in this immunosuppression is the essential inability to produce the T cell growth factor IL-2. In this study we demonstrate that this failure to produce IL-2 in response to mitogen stimulation is not the result of the absence of production of soluble or membrane-bound IL-1 by macrophages. Limiting dilution analysis of the precursor frequency of IL-2 producers suggests that an adequate number of precursors for IL-2 production are present in the spleens of infected mice, but that their activity may be regulated by suppressor cells. The presence of precursor cells for IL-2 production is supported by experiments showing that the combination of calcium ionophores and PMA elicits IL-2 production by spleen cells from both normal and T. cruzi-infected mice. Although Con A can provide either of the signals necessary for IL-2 production, calcium flux or protein kinase C activation, to T cells from normal mice, Con A in combination with either calcium ionophore or phorbol ester failed to activate T cells from infected mice to produce IL-2. Preculture of spleen cells from infected mice for 48 to 72 h before addition of Con A results in near normal production of IL-2. This recovery of the capacity to produce IL-2 does not occur if parasite Ag is present during the preculture period. These results suggest that the inability of T cells from T. cruzi-infected mice to produce IL-2 in vitro in response to Con A is not due to the lack of IL-2-producing cells, but may be the result of the maturational state of the T cells or to the presence of a suppressor population.

Topics: Animals; Calcimycin; Calcium; Chagas Disease; Concanavalin A; Ethers; Female; Immune Tolerance; Interleukin-2; Ionomycin; Lymphocyte Activation; Mice; Mice, Inbred C57BL; Protein Kinase C; Spleen; T-Lymphocytes; T-Lymphocytes, Regulatory; Tetradecanoylphorbol Acetate; Trypanosoma cruzi

Peripheral blood mononuclear cells (PBMC) isolated from chronic chagasic patients and control individuals in Recife, Brazil were examined for the ability to produce IL-2 in response to concanavalin A (Con A) stimulation. Overall, there was little difference in the range of the response (IL-2 production) between the chagasic and control groups. Within the chagasic group, however, there was a high negative correlation between IL-2 production and the level of anti-parasite antibody. This correlation is thought to be a reflection of the fact that individuals with more recent or more vigorous infections exhibit higher anti-parasite antibody responses but also display a greater degree of immunosuppression, as reflected in depressed IL-2 production.

Topics: Adult; Animals; Antibodies, Protozoan; Chagas Disease; Concanavalin A; Female; Humans; Immune Tolerance; In Vitro Techniques; Interleukin-2; Leukocytes, Mononuclear; Male; Middle Aged; Trypanosoma cruzi

Virtually nothing is known about the basis for the immunosuppression associated with human T. cruzi infection. We have used an in vitro system to explore this effect. Incubation of human peripheral blood mononuclear cells (PBMC) with blood forms of T. cruzi abrogated their responses to suboptimal, optimal and supraoptimal doses of Con A, PHA or PWM, whether or not monocytes were depleted. Killed parasites were not suppressive. Maximal suppression (74%) occurred when the parasites were present during the entire culture period (96 hr), although significant suppression (33%) was seen when the organisms were added 24, 48 or 72 hr after initiation, suggesting that the early stages of lymphocyte activation had been impaired and that a second generation of cells was also affected. The 4-day supernatant medium of a T. cruzi suspension supported PBMC responses to Con A as well as medium incubated alone, indicating that suppression did not result from parasite removal of essential nutrients. Furthermore, 96 hr after mitogenic stimulation, the proportions of viable PBMC in cultures containing or lacking the parasites were comparable. Although T. cruzi binds Con A and PHA, this absorption was not the cause of reduced responsiveness since optimal concentrations of Con A and PHA remained in solution under our conditions. Levels of IL-2 in PHA-stimulated PBMC cultures were markedly reduced in the presence of T. cruzi. However, exogenous IL-2 failed to restore lymphocyte responsiveness. T. cruzi neither absorbed nor inactivated IL-2. Thus, the noted suppression appeared to involve at least deficient production and utilization of IL-2.

Topics: Animals; Chagas Disease; Concanavalin A; Dose-Response Relationship, Immunologic; Immune Tolerance; Interleukin-2; Lymphocyte Activation; Lymphocytes; Mice; Mice, Inbred Strains; Mitogens; Thymidine

Mice infected with Trypanosoma cruzi develop immunosuppression with a deficient production of interleukin-2 (IL-2). In this situation the deficient concanavalin A (Con A) T-cell response is not corrected by addition of exogenous IL-2. Here we show that elimination of cycling cells by treatment of infected mice with hydroxyurea (HU) fully restored the ability of spleen cells to respond to IL-2. Further, capacity for IL-2 production was restored to HU treated infected mice, but not as completely as the response to IL-2.

Topics: Animals; Chagas Disease; Concanavalin A; Female; Hydroxyurea; Interleukin-2; Lymphocyte Activation; Male; Mice; Mice, Inbred Strains; Spleen; T-Lymphocytes

We investigated some aspects of the regulation of the immune response that were sensitive to the effect of indomethacin, an inhibitor of prostaglandin synthesis, in two groups of patients in the chronic phase of Chagas' disease, and in normal controls. One group of patients was defined as being infected but with no clinical evidence of cardiac involvement, while the other showed electrocardiographic alterations that are characteristic of Chagasic cardiomyopathy. The in vitro responses to mitogens (phytohemagglutinin and concanavalin A) and Trypanosoma cruzi antigens were evaluated in the presence or absence of indomethacin. It was found that the in vitro mitogenic stimulation by both phytohemagglutinin and concanavalin A of peripheral blood mononuclear cells from normal controls and infected and cardiomyopathic patients was significantly increased by indomethacin. An inverse correlation was found between the initial response to concanavalin A and the subsequent increase caused by the presence of indomethacin, for both the patients and the controls. Considering specific responses to T. cruzi antigens, we showed that in the presence of indomethacin these were significantly increased in infected patients, but not in cases of cardiomyopathy. Again, a significant inverse correlation was found between the basal responsiveness and the indomethacin-induced change. In general, infected patients showed changes in the presence of indomethacin that were most comparable to those of normal individuals. It would appear, therefore, that normal indomethacin-sensitive (prostaglandin-dependent) suppressor mechanisms operate in Chagas' patients. In certain cardiomyopathy patients, however, these control mechanisms may not operate; a possible consequence of this could be tissue damage.

Topics: Animals; Chagas Disease; Chronic Disease; Concanavalin A; Female; Humans; Indomethacin; Lymphocyte Activation; Male; Phytohemagglutinins; Reference Values; Trypanosoma cruzi

Topics: Animals; Antigens, Protozoan; Chagas Cardiomyopathy; Chagas Disease; Concanavalin A; Female; Humans; Immunity, Cellular; Lymphocyte Activation; Male; Phytohemagglutinins; T-Lymphocytes; Trypanosoma cruzi

The outcome of Trypanosoma cruzi infection in inbred strains of mice is under genetic control. The lymphocyte responses to T-cell mitogens and their regulation were investigated in strains of mice resistant or susceptible to T. cruzi. Six to eight days after the inoculation of T. cruzi, resistant and susceptible mice had depressed responses to T-cell mitogens. In resistant B6 mice, suppression was maximal 18 days after infection and it persisted for at least 320 days. The duration of immunosuppression correlated with the persistence of a subpatent parasitemia. In cell mixing experiments, it was determined that the concanavalin A (Con A) responses in the resistant B6 and B6C3F1 mouse strains were suppressed by highly active T-suppressor cells. In the susceptible C3H mice, intense suppression of the Con A responses was detected 14 days after inoculation of T. cruzi. Nevertheless, only weak suppressor cell activity was detected in the infected C3H mice, and suppression was not abrogated by passage through a nylon wool column nor by treatment with antitheta antibodies and complement. Thus, it was suggested that, during the course of infection with T. cruzi, splenic T cells from C3H mice acquired a block in the metabolic pathway for cellular activation by Con A. The influences of T. cruzi epimastigotes on the Con A responses of spleen cells from uninfected mice were then studied. The Con A responses of spleen cells from C3H mice were depressed in the presence of epimastigotes, whereas they were either unaffected or enhanced in spleen cells from B6 mice. Hence, the immunoregulatory events provoked by T. cruzi infection differed in genetically resistant and susceptible mice, and lymphocytes from C3H mice were predisposed to a parasite-induced block in the responses to Con A. Thus, the gene(s) determining the outcome of infection with T. cruzi may be phenotypically expressed through an influence on immunoregulatory events.

Topics: Animals; Chagas Disease; Concanavalin A; Female; Genes; Immune Tolerance; Immunity, Innate; Lymphocyte Activation; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; T-Lymphocytes; T-Lymphocytes, Regulatory

Infection of mice with Trypanosoma cruzi results in a severe immunosuppression, accompanied by the appearance of autoimmune symptoms. We have previously shown that proliferation and interleukin 2 production by concanavalin A-stimulated T cells from infected mice is severely depressed. In this study we show that at least two phenomena are responsible for this depression. First, mixing experiments showed the existence, in spleens of infected animals, of adherent, Thy-1-negative and radioresistant suppressor cells. Second, studies of enriched T cell populations and analysis of precursors by limiting dilution showed that the T cell compartment itself was impaired in infected animals: responses of enriched T cells, even when reconstituted with normal accessory cells, reached only 40% of those obtained with normal uninfected mice.

Topics: Animals; Catalase; Chagas Disease; Concanavalin A; Immune Tolerance; Indomethacin; Interleukin-2; Lymphocyte Activation; Macrophages; Male; Mice; Mice, Inbred C3H; T-Lymphocytes; T-Lymphocytes, Regulatory

Trypomastigote forms of Trypanosoma cruzi lose infectivity to cultured mammalian cells when exposed to tunicamycin. Upon reincubation into fresh medium, parasites recover their full penetration capacity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [35S]methionine-labeled polypeptides showed that tunicamycin-treated parasites present several components with altered electrophoretic mobility when compared with controls. Immunoprecipitation with rabbit hyperimmune and human chagasic sera indicated that the surface antigens of approximate molecular masses of 175-180, 120-125, 90-95 and 85 kDa are not encountered in tunicamycin-treated trypomastigotes. By affinity chromatography on wheat germ agglutinin-Sepharose, it was observed that the trypomastigote-specific 85 kDa glycoprotein (Tc-85) is affected by the drug. The other affected components are glycoproteins with affinity for concanavalin A. The results suggest that tunicamycin-sensitive surface glycoproteins from T. cruzi are involved in the parasite interiorization into mammalian cells.

Topics: Animals; Cell Line; Chagas Disease; Concanavalin A; Glucosamine; Glycoproteins; Host-Parasite Interactions; Humans; Immune Sera; Precipitin Tests; Protein Biosynthesis; Rabbits; Time Factors; Trypanosoma cruzi; Tunicamycin

The role of virulent forms of Trypanosoma cruzi in modulating mitogen-induced lymphocyte responses was investigated in this work. Bloodstream forms of T. cruzi inhibited normal mouse spleen cell responses to Con A and LPS in a dose-dependent manner. Reduced responses were observed over relatively large ranges of concentration of Con A (50-fold) and LPS (160-fold). The inhibitory action of the parasites could not be overcome by increasing the mitogen dose beyond optimal levels. Furthermore, absorption of mitogen solutions with four times as many parasites as used in the proliferation assays revealed that sufficient mitogen activity remained to produce optimal lymphocyte responses. Therefore, reduced lymphocyte responsiveness was not due to absorption of mitogen by the parasite. Inhibited responses were also seen when a sonicated T. cruzi preparation was used, indicating that parasite viability was not required to produce suppression. Inhibition of Con A- or LPS-induced responses by the parasites occurred only when the trypanosomes were incorporated into the system during the first 24 hr of culture. These results show that virulent forms of T. cruzi can induce suppression of T and B cell responses in vitro, and suggest that the parasite affects lymphocyte commitment to blastogenesis during the early stages of lymphocyte activation.

Topics: Animals; B-Lymphocytes; Chagas Disease; Concanavalin A; Female; Immune Tolerance; Lipopolysaccharides; Lymphocyte Activation; Mice; Mice, Inbred CBA; Mitogens; T-Lymphocytes; Trypanosoma cruzi

Acute infection of mice with Trypanosoma cruzi results in severe immunodepression and the appearance of autoimmune symptoms. In vitro, concanavalin A-stimulated T cells from spleens of infected animals could neither produce nor respond to interleukin 2. Interleukin 2 production was not restored by addition of exogenous interleukin 1, and proliferative response to concanavalin A was not restored by exogenous interleukin 2. A population of Thy-1-negative cells in the spleen of infected animals was shown to suppress the concanavalin A proliferative response and, to a lesser extent, the production of interleukin 2. These and other symptoms of T. cruzi-infected mice are similar to the immune dysfunction of autoimmune lpr/lpr mice. These findings are discussed in relationship to the pathology of Chagas disease.

Topics: Animals; Chagas Disease; Concanavalin A; Immunosuppression Therapy; Interleukin-2; Kinetics; Lymphocyte Activation; Male; Mice; Mice, Inbred Strains; Spleen; T-Lymphocytes; Trypanosoma cruzi

Infection of mice with Trypanosoma cruzi has been shown to lead to an impaired ability of lymphocytes to proliferate in response to mitogenic stimulation which is manifested during the acute period of the disease. A possible involvement of suppressor T lymphocytes has been postulated by other authors and was investigated in this work as a part of our efforts to disclose the mechanisms underlying the immunologic deficiency. Spleen cells from acutely infected CBA/J mice readily exhibited unresponsiveness to stimulation with concanavalin A, phytohaemagglutinin or a bacterial lipopolysaccharide. However, these cells were unable to reduce the responses that normal syngeneic-mouse spleen cells mounted to these mitogens when cultured together in equal proportions. Furthermore, removal of the Lyt 2.1-bearing cells, known to include the suppressor T cell subpopulation, from infected mouse splenocyte suspensions, did not alter the deficient responsive status of the remaining cells. These results, together with the severe depletion of the T-cell compartment which occurs in the spleens of animals acutely infected with T. cruzi, do not support an important role of suppressor T lymphocytes in the noted deficiency in lymphoid cell reactivity to mitogens. Reduced numbers of responder cells, intrinsic lymphocyte alterations or suppression by cells other than T lymphocytes remain plausible explanations to be explored.

Topics: Animals; Chagas Disease; Concanavalin A; Female; Lipopolysaccharides; Lymphocyte Activation; Mice; Mice, Inbred CBA; Phytohemagglutinins; T-Lymphocytes, Regulatory

Antigen-stimulated peripheral blood mononuclear cells from 14 patients with chronic Chagas' disease were examined for their ability to generate soluble factor(s) capable of activating human macrophages to a microbicidal state. Mononuclear cell factors (MCF) from all but one patient were capable of inducing macrophages to a state where they were able to kill trypomastigotes of Trypanosoma cruzi. Macrophage microbicidal activity against this organism was nonspecific, because it could be induced by lymphokine from PPD-positive subjects exposed to heat-killed BCG or by concanavalin A stimulation of normal donors cells. A factor(s) generated by the stimulation of mononuclear cells from normal donors by T. cruzi antigen did not induce macrophage microbicidal activity. Opsonization of the organisms with specific IgG did not alter their fate in normal macrophages, but enhanced their killing in MCF-activated cells. Induction of macrophage activation in the human system differed from the results previously described in mice in a few features: 1) Optimal microbicidal activity did not require daily addition of the soluble factors. 2) The MCF dose-response curve was shifted to lower concentrations. 3) MCF activity generated by antigen-stimulated peripheral blood lymphocytes correlates with their proliferative responses to antigen. Half of the patients showed low proliferative responses and correspondingly lower MCF activity. Mitogen responses were normal in all patients. No correlation was found between low or high responses and clinical manifestations of disease.

Topics: Animals; BCG Vaccine; Blood Proteins; Cells, Cultured; Chagas Disease; Chronic Disease; Concanavalin A; Humans; Immunoglobulin G; Lymphocyte Activation; Macrophages; Mice; Mice, Inbred A; Monocytes; Phagocytes; Receptors, Fc; Time Factors; Trypanosoma cruzi

Infection with Trypanosoma cruzi decreases the ability of spleen cells from mice to respond to either T cell, concanavalin A (Con A), or B cell, lipopolysaccharide (LPS), mitogens. The effect of infection on the mitogenic response depends on the elapsed time between the day of infection and the time of mitogen presentation. Responses early in infection are normal, whereas later responses to either mitogen are depressed. Spleen cells from late trypanosome-infected mice inhibit the ability of normal spleen cells to respond to Con A or LPS. The cell in the T. cruzi-infected spleen cells responsible for this effect is nonadherent, sensitive to treatment with anti-mouse thymus serum plus complement, but insensitive to treatment with anti-immunoglobulin plus complement. These data indicate that infection with T. cruzi elicits over time the generation of T cells suppressive to T and B cell mitogenic responses.

Topics: Animals; Antilymphocyte Serum; Cell Adhesion; Chagas Disease; Complement System Proteins; Concanavalin A; DNA; Lipopolysaccharides; Lymphocyte Activation; Male; Mice; Mice, Inbred BALB C; Spleen; T-Lymphocytes; Trypanosoma cruzi

Topics: Agglutination; Animals; Blood; Chagas Disease; Concanavalin A; Culture Media; Glucosamine; Glucose; Mannose; Methylglycosides; Mice; Spectrophotometry; Trypanosoma cruzi; Trypsin