B cell activation. III. B cell plasma membrane depolarization and hyper-Ia antigen expression induced by receptor immunoglobulin cross-linking are coupled.

Abstract

The relationship between ligand-induced B cell plasma membrane depolarization and increased expression of membrane-associated, I-A subregion encoded (mI-A) antigens was investigated. 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. A cause- and-effect relationship between these 2 events is suggested by results that demonstrate that inhibition of anti-Fab-induced depolarization by valinomycin also inhibit 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. Antigen-mediated receptor cross-linking apparently 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.