B cell activation. III. B cell plasma membrane depolarization and hyper-Ia antigen expression induced by receptor immunoglobulin cross-linking are coupled.
We report investigation of the relationship between ligand-induced B cell plasma membrane depolarization and increased expression of membrane-associated, I-A subregion encoded (mI-A) antigens. Results demonstrate that equal frequencies of B cells are stimulated to undergo membrane depolarization and to increase mI-A expression in response to mitogen, anti-Ig, and thymus-independent (TI) or thymus-dependent (TD) antigens. Further, a cause-and-effect relationship between these two events is suggested by results that demonstrate that inhibition of anti-Fab--induced depolarization by valinomycin also inhibits the subsequent increase in mI-A antigen expression and "passive" (non-ligand-mediated) depolarization of murine B cells by K+ results in hyper-mI-A antigen expression. Based upon these results we hypothesize that antigen-mediated receptor cross-linking results in signal transduction via membrane depolarization, which is resultant in increased mI-A antigen synthesis and cell surface expression. This increase in mI-A antigen density may render the B cell more receptive to subsequent interaction with I-region-restricted helper T cells.
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D005786:Gene Expression Regulation; D005802:Genes, MHC Class II; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007136:Immunoglobulins / Q000276:immunology*; D008213:Lymphocyte Activation; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008934:Mitogens / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011971:Receptors, Immunologic / Q000276:immunology*; D014634:Valinomycin / Q000494:pharmacology
D000949:Histocompatibility Antigens Class II; D007140:Immunoglobulin Fab Fragments; D007136:Immunoglobulins; D008934:Mitogens; D011971:Receptors, Immunologic; D014634:Valinomycin; D011188:Potassium