Activated T cells induce rapid CD83 expression on B cells by engagement of CD40.

The conserved transmembrane glycoprotein CD83 was originally described as highly specific marker for mature dendritic cells in the peripheral circulation. Besides its regulatory role in thymic T cell maturation and peripheral T cell activation, recent studies suggest, that CD83 is also involved in the regulation of B cell maturation, homeostasis and function. Here we show, that antigen-specific T cell stimulation leads to CD83 induction predominantly on B cells. In vivo activation of T cells by injection of cognate antigenic peptide into T cell receptor transgenic mice induced strong expression of the early activation marker CD69 but only low levels of surface CD83 on T cells. In contrast CD83 was induced on 80% of B cells in the draining lymph node. This T cell mediated induction of CD83 expression on B cells was not mediated by soluble factors but was contact dependent because separation of B cells from an ongoing T cell stimulation in a transwell system abrogated CD83 expression. Since CD83 expression was induced on both MHC-matched and MHC-mismatched B cells present in cultures of activated T cells, cell contact via TCR/MHC binding was not essential. The application of an antibody to the CD40 ligand of T cells, however, strongly interfered with the induction of CD83 expression on bystander B cells. Taken together we provide evidence that activated T cells induce CD83 on B cells via CD40 engagement but independent of TCR/MHC binding and thus independent of antigen-specificity of B cells.