The requirements for growth of in vivo activated autoimmune B cells are similar to those of in vitro generated lipopolysaccharide B cell blasts and dissimilar to anti-IgM plus IL-4 induced B lymphoblasts.
The requirements for growth of in vivo activated B cells (natural blasts) from autoimmune NZB/W mice and of B cells from the same animals activated in vitro with either LPS or anti-IgM plus IL4 (mimicking 'in vitro' antigen induced TH cell-B cell interaction) were studied comparatively. The proliferation of natural and LPS blasts was inhibited by anti-IgM antibodies and augmented by recombinant IL-5. In contrast, anti-IgM stimulated the growth of anti-IgM plus IL-4 primed B cells but was without effect on the proliferative responses in the presence of IL-5. The growth inhibition induced by anti-IgM signalling on natural and LPS blasts seemed to be due to cross-linking of sIg rather than to binding of anti-IgM antibodies to the Fc receptors since a similar effect was observed with the F(ab)'2 fragment of this molecule. Maximum proliferation was obtained by a combination of IL-4 and IL-5 in natural and LPS blasts, whereas peak responses in anti-IgM plus IL-4 blasts were achieved by a combination of anti-IgM and IL-4. Lymphoblasts recovered after preculturing natural blasts in medium alone (more differentiated in vivo activated B cells) displayed high spontaneous proliferation which was strongly inhibited by anti-IgM. This inhibition was reversed partially by IL-4 and totally by IL-5. To define better the role of BLy+ cells in the spleen of NZB/W mice, purified Ly1+ and Ly1- cells, obtained by separation using magnetic beads, were analysed. The growth of both cell subpopulations was inhibited by anti-IgM and enhanced by IL-5. Cytotoxic elimination of Ly1+ cells from the primed B blast populations did not modify the proliferative pattern of these cells. Our results show that the growth requirements of in vivo activated autoimmune B cells resemble those of LPS blasts and differ from those following stimulation with anti-IgM plus IL-4, suggesting that B cells in systemic autoimmune diseases may have been activated by polyclonal stimulation. Nevertheless, other mechanisms for autoimmune B cell activation cannot be ruled out by the present experimental approach.
Cabrero
E
E
Department of Immunology, Hospital General Gregorio Marañón, Universidad Complutense de Madrid, Spain.
Sánchez
M J
MJ
Gutiérrez
C
C
D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology*; D001327:Autoimmune Diseases / Q000235:genetics / Q000276:immunology*; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004357:Drug Synergism; D005260:Female; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D007376:Interleukin-2 / Q000494:pharmacology; D015847:Interleukin-4 / Q000494:pharmacology*; D015848:Interleukin-5 / Q000494:pharmacology; D008070:Lipopolysaccharides; D008213:Lymphocyte Activation / Q000187:drug effects; D008297:Male; D051379:Mice; D008814:Mice, Inbred NZB / Q000235:genetics / Q000276:immunology*; D008817:Mice, Mutant Strains / Q000235:genetics / Q000276:immunology*; D011994:Recombinant Proteins / Q000494:pharmacology; D013154:Spleen / Q000276:immunology
D000888:Antibodies, Anti-Idiotypic; D007140:Immunoglobulin Fab Fragments; D007075:Immunoglobulin M; D007376:Interleukin-2; D015848:Interleukin-5; D008070:Lipopolysaccharides; D011994:Recombinant Proteins; D015847:Interleukin-4