A Trypanosoma cruzi alkaline antigen induces polyclonal B-cell activation of normal murine spleen cells by T-cell-independent, BCR-directed stimulation.
We have previously reported that a cytosolic alkaline fraction (FI) obtained from epimastigotes of Trypanosoma cruzi promotes the activation, proliferation and differentiation of normal murine B cells into antibody-secreting plasmocytes. Neither the mechanism nor the cells involved in the FI-induced polyclonal B-cell activation were established. In this work we report that accessory cells are required for FI-induced polyclonal B-cell activation as no proliferative responses were obtained following treatment of normal spleen mononuclear cells (NSMC) with L-leucine methyl ester. Furthermore, FI did not induce the expression of CD25 on T cells and it promoted the proliferation of a T-cell-depleted population, indicating that it acts in a T-independent manner. We observed that NSMC were stimulated in vitro by FI-released cytokines, such as interleukin (IL)-4, IL-6 and IL-10, which are involved in B-cell proliferation and differentiation. Interestingly, while significant amounts of interferon-gamma (IFN-gamma) were found in culture supernatants we did not observe detectable levels of IL-2. Additionally, we found that B-cell receptor (BCR) and major histocompatibility complex (MHC) class II antigens were involved in the proliferative response induced by FI because antibodies directed against cell-surface immunoglobulin M (IgM), CD45 and MHC class II molecules inhibited the FI-induced B-cell proliferation. CD40 ligand (CD40L) did not participate in such a phenomenon.
Montes
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CL
Inmunología, Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba Argentina.
Zuñiga
E
E
Minoprio
P
P
Vottero-Cima
E
E
Gruppi
A
A
D000818:Animals; D000953:Antigens, Protozoan / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D023201:CD40 Ligand; D002455:Cell Division; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D007148:Immunoglobulin mu-Chains / Q000276:immunology; D017493:Leukocyte Common Antigens / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D008562:Membrane Glycoproteins / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D011947:Receptors, Antigen, B-Cell / Q000276:immunology*; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D014349:Trypanosoma cruzi / Q000276:immunology*
D000953:Antigens, Protozoan; D000949:Histocompatibility Antigens Class II; D007148:Immunoglobulin mu-Chains; D008562:Membrane Glycoproteins; D011947:Receptors, Antigen, B-Cell; D015375:Receptors, Interleukin-2; D023201:CD40 Ligand; D017493:Leukocyte Common Antigens