muramidase and Lymphopenia

Sarcoidosis is a multisystem granulomatous disease of unknown origin. No single biological marker allows definitive diagnosis of sarcoidosis or may accurately predict the disease prognosis. However, some biological markers are helpful tools as diagnostic aids and disease activity markers. At the blood level, lymphopenia with CD4 depletion, elevated levels of serum-angiotensin converting enzyme, lyzozyme, beta 2 microglobulin and disturbed calcium metabolism resulting in hypercalcemia and hypercalciuria can help guide diagnosis. Lymphocytic alveolitis with a high CD4/CD8 ratio in bronchoalveolar lavage fluid is highly suggestive of the disease. A wide range of new biological markers are proposed but their pronostic significance is still controversial. In clinical practice, biological markers may help in monitoring treated patients with sarcoidisis.

Topics: beta 2-Microglobulin; Biomarkers; CD4 Lymphocyte Count; Humans; Hypercalcemia; Lymphopenia; Muramidase; Peptidyl-Dipeptidase A; Prognosis; Reproducibility of Results; Sarcoidosis; Sensitivity and Specificity

Topics: Dysgammaglobulinemia; Humans; IgA Deficiency; IgG Deficiency; Immunoglobulin M; Immunologic Deficiency Syndromes; Lung; Lung Diseases; Lymphopenia; Muramidase; T-Lymphocytes

The transitional stage is a key check-point for elimination of autoreactive B cells in the periphery. This selection process requires fine regulation of signals received through BCR and B cell activating factor (BAFF) receptor. We previously identified the adaptor molecule Act1 as a negative regulator of BAFF-mediated signaling. Deficiency of Act1 in mice results in peripheral B cell hyperplasia and development of autoimmunity. In this study, we demonstrate that Act1 plays a critical role in the regulation of transitional B cell survival and maturation. We found that the ratio of late-transitional (T2) to early-transitional (T1) cells was increased in spleens from Act1-deficient mice. Moreover, BAFF stimulation induced better T1 cell survival and promoted more efficient maturation of T1 cells into T2 cells ex vivo in the absence of Act1. BAFF stimulation induced higher levels of the anti-apoptotic Bcl-2 member Mc1-l in Act1-deficient T1 cells than in wild-type control cells, suggesting that Mcl-1 might be one of the key effector molecules for BAFF-mediated survival of the Act1-deficient transitional B cells. Importantly, costimulation with BAFF was able to rescue Act1-deficient T1 cells from BCR-induced apoptosis more effectively than Act1-sufficient T1 B cells. Finally, by using hen egg lysozyme double transgenic mice, we demonstrated that Act1 deficiency can promote the maturation of Ag-specific autoreactive B cells. Taken together, our results suggest that the transitional stage is a critical point of action of Act1 in the elimination of autoreactive B cells and in the regulation of peripheral B cell homeostasis.

Topics: Adaptor Proteins, Signal Transducing; Animals; B-Cell Activating Factor; B-Lymphocyte Subsets; Cell Differentiation; Cell Survival; Cells, Cultured; Homeostasis; Lymphopenia; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Muramidase

Immunization with the hen egg-white lysozyme (HEL) protein induces T cells to various of its peptide determinants. The distribution of such T cells, however, does not correlate with the peptide level of each epitope on class II molecules. For this reason, we sought information on the cells responsible for Ag presentation following immunization, hoping to understand the lack of immunodominance in this system. By tracking HEL, and the ensuing peptide/MHC complexes, we find the following: 1) that HEL in the draining lymph node gets concentrated in a limited number of APC, particularly in dendritic cells and macrophages, 2) that these APC are functionally capable of presenting both major and minor determinants of HEL over a 100-fold range of Ag dose, and 3) that B cells present Ag gained at early times after immunization, but only following higher dose immunization. These data indicate that the breadth of a response is maintained over a wide dosage range by concentration of Ag in a limited number of cells presenting high levels and a great diversity of epitopes.

Topics: Animals; Antigen Presentation; Antigen-Presenting Cells; Antigens; B-Lymphocyte Subsets; Epitopes, T-Lymphocyte; Histocompatibility Antigens Class II; Immunization; Immunodominant Epitopes; Injections, Subcutaneous; Iodine Radioisotopes; Lymphocyte Count; Lymphopenia; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Muramidase; T-Lymphocyte Subsets

To determine the effects of chronic Ag stimulation on B cell survival and phenotype, we compared survival and surface markers of hen egg lysozyme (HEL)-specific B cells in Ig transgenic (Tgn) mice, which lack HEL, and in HEL-Ig transgenic mice, which express soluble HEL. Serum HEL levels were maximized in HEL-Ig Tgn mice by feeding them zinc, which activates the metallothionein promoter that regulates HEL expression. B cell age was characterized by expression of heat-stable Ag, and B220 and B cell survival was studied by evaluating changes in B cell number when lymphopoiesis was suppressed with anti-IL-7 mAb and by identifying newly generated B cells through 5-bromo-2'-deoxyuridine incorporation. Our observations show that the mean B cell life span is considerably reduced in HEL-Ig Tgn compared with Ig Tgn mice, but also demonstrate that some HEL-Ig Tgn B cells survive to maturity. Some of these surviving B cells have undergone receptor editing (substitution of an endogenous Ig light chain for the transgenic Ig light chain), so that their ability to bind HEL is decreased or absent. Surviving HEL-Ig Tgn B cells that retain HEL specificity express decreased mIgD and little or no mIgM. mIgD expression progressively decreases with increasing HEL-Ig Tgn B cell age. These observations suggest that self Ag-specific B cells can survive in the presence of soluble self Ag by down-regulating mIg expression, which should limit B cell signaling by Ag that might otherwise cause deletion of these cells.

Topics: Animals; Antibodies, Monoclonal; B-Lymphocytes; Binding Sites, Antibody; Bromodeoxyuridine; Cell Differentiation; Cell Survival; Female; Immunoglobulin D; Immunoglobulin M; Immunophenotyping; Injections, Intraperitoneal; Interleukin-7; Lymphocyte Depletion; Lymphopenia; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Muramidase; Receptors, Antigen, B-Cell; Spleen; Time Factors

In mice with a diverse B cell repertoire, hen egg lysozyme (HEL) autoantigen-binding B cells are excluded from follicles and eliminated in 3 days. To explore the roles of competitor B cells and of T cells in this mechanism of self-tolerance, HEL-specific B cells were transferred into mice containing HEL and deficient in endogenous B cells (muMT), T cells (TCR-/-), or B and T cells (RAG1-/-). Previous studies suggested a dual requirement for B cell receptor (BCR) engagement and competition in HEL autoantigen-binding B cell elimination, but interpretation of these experiments has been confounded by the possible failure to independently regulate autoantigen concentration and competitor B cell frequency. In experiments in this study, we have fixed one variable, HEL concentration, while varying the second, the presence or absence of other B cells. By this approach, we find that follicular exclusion and rapid elimination of autoreactive B cells require BCR engagement plus competition with other B cells, rather than BCR engagement alone. We also find, by transfers into T cell-deficient mice, that T cells are not required for this peripheral tolerance mechanism. Unexpectedly, in mice lacking both T cells and competitor B cells (RAG1-/-), transferred HEL-binding cells survive less well than in mice just lacking competitor B cells. These results suggest T cells can enhance autoreactive B cell survival. Enhanced survival of autoreactive B cells, due to the presence of T cells and the lack of competitor B cells, might contribute to the elevated frequency of autoimmunity in B cell-deficient individuals.

Topics: Animals; Autoantigens; B-Lymphocyte Subsets; Binding, Competitive; Cell Movement; Cell Survival; Chickens; Lymphoid Tissue; Lymphopenia; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Muramidase; T-Lymphocyte Subsets

The mechanisms accounting for T cell depletion in AIDS patients are not yet fully understood, nor are the roles of host factors in HIV pathogenesis. We show here that an ongoing humoral immune response to HIV gp120 can sensitize non-infected cells towards apoptosis. Thus, i.v. injection of 1 microg recombinant(r) gp120 into gp120-immunized human CD4-transgenic mice (huCD4 Tg), which express huCD4 on both T and B cells, results in T and B cell depletion in peripheral blood and lymphoid tissues. On day 6 after a bolus injection of gp120, the numbers of peripheral T cells and B cells in gp120-immunized huCD4 Tg decreased sevenfold and two- to threefold, respectively. Annexin V staining revealed a higher percentage of early apoptotic cells on day 1 of gp120 i.v. injection from gp120-primed huCD4 Tg spleens compared to gp120-primed controls. Boosting the primed huCD4 Tg mice with soluble gp120 and hen egg-white lysozyme led to lower secondary titers to both antigens than found in controls. Furthermore, splenocytes from gp120-pretreated immunized huCD4 Tg had a lower level of stimulation in response to anti-CD3 treatment. These in vivo results are consistent with in vitro data demonstrating that cross-linking CD4 on splenocytes of huCD4 Tg by rgp120SF2 and anti-gp120 not only sensitizes T cells for apoptosis, but also induces apoptosis per se, and suggest that anti-gp120 responsiveness can contribute to T cell depletion in AIDS.

Topics: Animals; Apoptosis; B-Lymphocytes; CD3 Complex; CD4 Antigens; CD4 Lymphocyte Count; Female; HIV Antibodies; HIV Envelope Protein gp120; HIV Infections; Humans; Immunization; In Vitro Techniques; Injections, Intravenous; Lymphoid Tissue; Lymphopenia; Male; Mice; Mice, Inbred BALB C; Mice, Transgenic; Muramidase; Recombinant Proteins; T-Lymphocytes

Topics: Abortion, Septic; Adjuvants, Immunologic; Adult; Endometritis; Female; Humans; Lymphopenia; Muramidase; Pregnancy; T-Lymphocytes

Topics: Adjuvants, Immunologic; Animals; Cattle; Female; Lymphopenia; Male; Mice; Mice, Inbred C57BL; Muramidase; Trypsin; Vibration

Topics: Adaptation, Physiological; Adrenocortical Hyperfunction; Alanine Transaminase; Alkaline Phosphatase; Aspartate Aminotransferases; Bacterial Vaccines; Blood Coagulation Disorders; Blood Glucose; Blood Protein Disorders; Child; Cholesterol; Complement System Proteins; Electrolytes; Eosinophils; Humans; Hyperlipidemias; Leukocytosis; Lymphopenia; Muramidase; Neurologic Manifestations; Phagocytosis; Properdin; Thrombocytosis; Toxoids; Transferrin; Vaccination; Viral Vaccines