Dendritic cell-B-cell interaction: dendritic cells provide B cells with CD40-independent proliferation signals and CD40-dependent survival signals.

Dendritic cells (DC) have recently been shown to play an important role in B-cell function. We have previously shown that DC can capture and retain unprocessed antigen in vitro and in vivo, and can transfer this antigen to naive B cells to initiate antigen-specific antibody responses. We also demonstrated that DC were providing B cells with isotype-switch signals independent of T cells but that T-cell help was essential for antibody production. In this study, using B cells and DC from wild type (WT) and CD40 knockout (CD40KO) mice we show that DC initiate proliferation of B cells independently of CD40, because WT or CD40KO DC could induce proliferation of WT or CD40KO B cells, but proliferation was greater in the absence of CD40. DC also provide B cells with survival signals as WT DC improved viability of B cells after a 5-day culture but survival was reduced in the absence of CD40 expression.