concanavalin-a and Toxoplasmosis

Considerable evidence documents the importance of co-factors, including the immune response, in expression of oncogenicity of tumour viruses. To determine whether a common protozoal infection that can depress lymphocyte function alters manifestations of oncogenic virus infection, a mouse model of Toxoplasma infection with depressed T lymphocyte function was developed. In this model, Toxoplasma depressed blastogenic transformation to the T-cell mitogen Concanavalin A and primary antibody response to sheep red blood cells which requires T cell help. Uninfected and Toxoplasma-infected mice were then infected with Moloney leukaemia or Moloney sarcoma viruses and development of lymphoma and sarcoma were evaluated. Toxoplasma infection, which induced depression of T-cell function, decreased the incidence of Moloney sarcoma virus induced rhabdomyosarcomas but did not alter progression or regression of tumour in those mice that developed tumour. Conjoint infection with Toxoplasma and Moloney leukaemia virus did not increase incidence of lymphoma when compared with incidence of lymphoma in mice infected with Moloney leukaemia virus alone.

Topics: Animals; Antibody Formation; Concanavalin A; Female; Leukemia, Experimental; Lymphocyte Activation; Lymphoma; Mice; Mice, Inbred BALB C; Moloney murine leukemia virus; Moloney murine sarcoma virus; Rhabdomyosarcoma; Sarcoma, Experimental; T-Lymphocytes; T-Lymphocytes, Helper-Inducer; Thymus Gland; Toxoplasmosis

Detection of antigenspecific suppressor cells in Toxoplasma infection of man. Investigations adapted to demonstrate the action of antigen-specific suppressor cells were carried out in subjects with acute toxoplasmosis (n = 5) and latent infections (n = 16) and compared to non-infected controls (n = 11). The investigations were carried out in vitro in the form of autologous one-way lymphocyte mixed culture. Suppressor cells were activated by toxoplasma lysate antigen (325 micrograms/ml) and, for comparison, by concanavalin A (10 micrograms/ml). Responder cells were stimulated by toxoplasma lysate antigen (200 micrograms/ml). In the acute cases, antigen-specific suppressor cells were identified which caused the lymphocyte transformation to be suppressed (tritium thymidine incorporation) to the same extent as did the mitogen-activated cells. The subjects with latent infections revealed a statistically significant difference (p less than 0.01) between the means of the percentage suppression of suppressor cells activated by toxoplasma lysate antigen or concanavalin A, suggesting a diminishing suppressive action of antigen-specific cells at this stage of infection. In addition to the effect on phagosome formation in macrophages, the activation of suppressor cells too should be considered as a factor of virulence for Toxoplasma gondii.

Topics: Acute Disease; Adult; Animals; Antigens, Protozoan; Concanavalin A; Epitopes; Female; Humans; Lymphocyte Activation; Lymphocyte Culture Test, Mixed; Male; T-Lymphocytes, Regulatory; Toxoplasma; Toxoplasmosis

Mononuclear phagocytes, particularly macrophages (M phi) that have been activated by lymphokines, are the principal defense against intracellular pathogens such as Toxoplasma gondii. To determine reasons for the newborns' susceptibility to Toxoplasma infection, we compared: the interaction of Toxoplasma with newborns' mononuclear phagocytes (blood monocytes and two types of newborn M phi, those derived from blood monocytes or from placental tissue) with adults' blood monocytes and monocyte-derived M phi and the production of M phi-activating lymphokines (MAF) by Concanavalin A (ConA)-stimulated newborn and adult blood mononuclear cells (MC). Newborn and adult monocytes killed Toxoplasma with equal efficiency. Similarly, survival and replication of Toxoplasma were comparable in control newborn and adult M phi. Exposure to adult ConA supernatants significantly decreased the survival and replication of Toxoplasma both in adult and newborn M phi. In contrast, exposure to cord blood ConA supernatants failed to affect the survival or the replication of Toxoplasma in newborn M phi and decreased the replication but not the survival of Toxoplasma in adult M phi. Exposure to ConA supernatants of peripheral blood MC from 2-5-d old newborns failed to affect survival or replication of Toxoplasma in newborn or adult M phi. Thus, both generation of MAF by newborn blood MC and response to newborn MAF by newborn M phi were impaired. Generation of MAF by adult blood mononuclear cells was not inhibited by cord blood MC nor was generation of MAF by cord blood MC increased by depletion of OKT8 antibody-binding cells, by depletion of adherent cells with or without addition of adult adherent cells, or by addition of indomethacin. Depletion of OKT4 antibody-binding cells abrogated the generation of MAF both by adult and cord blood MC. The activity of adult ConA supernatants was abrogated by dialysis at pH 2 or by addition of anti-gamma-interferon but not anti-alpha-interferon antibody. However, the correlation between antiviral interferon activity and anti-Toxoplasma activity was weak (r = 0.40). Enhanced M phi anti-Toxoplasma activity was not associated with detectably enhanced superoxide anion generation, nitroblue tetrazolium reduction, or phagolysosome fusion, and was not inhibited by catalase, superoxide dismutase, or mannitol. These results indicate that generation of and response to MAF is decreased in cells from human newborns and that gamma-interferon may be the major M

Topics: Adult; Cells, Cultured; Concanavalin A; Female; Fetal Blood; Fetus; Fibroblasts; Humans; Immunity, Innate; Infant, Newborn; Lymphocytes; Lymphokines; Macrophage Activation; Macrophages; Monocytes; Nitroblue Tetrazolium; Pregnancy; Superoxides; Toxoplasmosis

Topics: Adolescent; Adult; Antigens; Child; Concanavalin A; Female; Humans; Infectious Mononucleosis; Lectins; Lymphocyte Activation; Lymphocytes; Male; Middle Aged; Pokeweed Mitogens; Toxoplasma; Toxoplasmosis; Toxoplasmosis, Ocular

Topics: Animals; Cell Separation; Cell-Free System; Concanavalin A; DNA; Epitopes; Lymphocyte Activation; Macrophages; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Neoplasms, Experimental; Phosphorus Radioisotopes; Propionibacterium acnes; Thymidine; Time Factors; Toxoplasma; Toxoplasmosis; Tritium

In vitro assessments were carried out to study some biological aspects of immune lymphocytes producing a new lymphokine, called by the authors Toxoplasma growth inhibitory factor (Toxo-GIF), which inhibits the intracellular multiplication of Toxoplasma gondii within nonimmune mouse macrophages. Concanavalin A and phytohemagglutinin-P were found to induce vigorous production of Toxo-GIF, whereas bacterial lipopolysaccharide did not. In vitro treatment of splenic lymphocytes with rabbit anti-mouse thymocyte serum plus complement abolished almost completely their ability to produce Toxo-GIF. Treatment of splenic lymphocytes with inhibitors of protein synthesis, cycloheximide or puromycin resulted in a remarkable reduction of the ability of sensitized lymphocytes to produce this lymphokine. Thus the production of Toxo-GIF seems to be dependent on the cellular metabolic events of sensitized T-lymphocytes. The significant activity of Toxo-GIF was demonstrable even in the supernate of lymphocyte cultures incubated in serum-free medium and was also evident after immune lymphocytes and homologous antigen were incubated for the relatively short period of 10 h.

Topics: Animals; Antilymphocyte Serum; Cell Division; Cells, Cultured; Concanavalin A; Cycloheximide; Lectins; Lipopolysaccharides; Lymphocytes; Lymphokines; Macrophages; Male; Mice; Polysaccharides, Bacterial; Puromycin; Spleen; T-Lymphocytes; Toxoplasma; Toxoplasmosis

Evidence for the presence of carbohydrate on the surface membrane of Toxoplasma gondii trophozoites and on the cell wall of toxoplasma brain cysts was sought by fluorescent lectin staining. Using FITC-conjugated preparations of Concanavalin A (Con A), wheat germ agglutinin (WGA), or soy bean agglutinin (SBA), we have failed to obtain evidence for the binding of these lectins on the surface of T. gondii trophozoites. In contrast, the three test lectins bound effectively and specifically to the wall of toxoplasma brain cysts. Prefixation of cysts with glutaraldehyde or brief trypsinization of cysts did not affect the intensity of cyst wall fluorescence when stained with FITC-conjugated Con A, SBA, or WGA. The results are interpreted to indicate that whereas exposed Con A, SBA, and WGA binding sites are associated with the wall of toxoplasma brain cysts, such lectin-binding saccharide residues are not present on the surface of trophozoites in exposed or reactive form.

Topics: Animals; Binding Sites; Brain; Concanavalin A; Female; Fluoresceins; Humans; Lectins; Mice; Toxoplasma; Toxoplasmosis

A plate hemolysin test was developed to screen serum specimens for the presence of toxoplasma antibodies. When we tested 130 sera by both this test and the standard toxoplasma dye test, we found the plate hemolysin test to be a rapid, sensitive, and economical method for detecting toxoplasma antibodies. In all but one instance it paralleled the dye test. A comparison of the results of testing six sera by the hemolysin, hemagglutination, and dye-test techniques suggested that the hemolytic antibodies were more closely related to hemagglutinating antibodies than to dye-test antibodies. We could not store sheep erythrocytes sensitized with toxoplasma lysate for more than 3 days without altering the sensitivity of the test. Concanavalin A proved to be an effective coupling agent for binding toxoplasma antigens to red-cell membranes, a quality attributed to its affinity for specific polysaccharide-combining sites.

Topics: Animals; Antibodies; Concanavalin A; Erythrocytes; Evaluation Studies as Topic; Hemagglutination Tests; Hemolysin Proteins; Humans; Methods; Methylene Blue; Mice; Serologic Tests; Sheep; Toxoplasma; Toxoplasmosis; Toxoplasmosis, Ocular