Outside inside signalling in CD40-mediated B cell activation.

CD40 is a member of the growing tumor necrosis factor receptor (TNF-R) family of molecules, and has been shown to play important roles in T cell-mediated B lymphocyte activation. Ligation of B cell CD40 by CD154 expressed on activated T cells stimulates B cell proliferation, differentiation, isotype switching, upregulation of surface molecules contributing to antigen presentation, development of the germinal center, and the humoral memory response. The present review will summarize recent literature data on the various CD40 signalling pathways, which involve both the TNF-R associated factors (TRAFs) and additional signalling proteins, and lead to activation of kinases and transcription factors.