A role for T cell CD4 in contact mediated T dependent B cell activation.
Using a monoclonal antibody to CD4 we have shown that occupation of CD4 on T cells induces a strong dose dependent inhibition of in vitro IgM plaque forming cell (PFC) response of spleen cells to the T dependent antigen (Ag), sheep red blood cells (SRBC), in Mishell-Dutton cultures. This inhibitory effect is not due simply to nonspecific perturbation or Fc binding, since F(ab) fragments of anti-CD4 are as potent as the intact antibodies, whereas antibodies to class I molecules or T cell CD5 have no effect. The anti-CD4 antibody appears to block contact dependent interaction between T and B cells and this inhibitory effect cannot be overcome by cytokines. Anti-CD4 did not inhibit the PFC response to the T independent antigen, trinitrophenylated lipopolysaccharide. The anti-CD4 antibody prevented the interaction of preactivated fixed SRBC specific T helper cells with B cells, suggesting that CD4 had a role in contact mediated interactions between T cells and B cells. Surprisingly, antibodies to CD40L failed to inhibit the SRBC specific PFC response. Thus CD4 appears to be an important molecule required for cognate interactions between T and B cells that are needed to generate an Ag specific PFC response.
Department of Microbiology and Immunology, University of Kentucky, Lexington 40536-0230, USA.
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Kruman
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Ramiya
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Bondada
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D015704:CD4 Antigens / Q000276:immunology*; D023201:CD40 Ligand; D018956:CD5 Antigens / Q000276:immunology; D002478:Cells, Cultured; D004912:Erythrocytes / Q000276:immunology; D005260:Female; D006462:Hemolytic Plaque Technique; D007128:Immunoglobulin Fragments / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D008562:Membrane Glycoproteins / Q000276:immunology; D051379:Mice; D008811:Mice, Inbred DBA; D051381:Rats; D012756:Sheep; D013601:T-Lymphocytes / Q000276:immunology*
D015704:CD4 Antigens; D018956:CD5 Antigens; D007128:Immunoglobulin Fragments; D007075:Immunoglobulin M; D008562:Membrane Glycoproteins; D023201:CD40 Ligand