CD40 Expression by B cells is Required for Optimal Immunity to MurinePneumocystisInfection

Abstract

AbstractCD40-CD40L interactions are critical for controllingPneumocystisinfection. However, which CD40-expressing cell populations are important for this interaction have not been well-defined. We used a cohousing mouse model ofPneumocystisinfection, combined with flow cytometry and qPCR, to examine the ability of different populations of cells from C57BL/6 mice to reconstitute immunity in CD40 knockout (KO) mice. Unfractionated splenocytes, as well as purified B cells, were able to controlPneumocystisinfection, while B cell depleted splenocytes and unstimulated bone-marrow derived dendritic cells (BMDCs) were unable to control infection in CD40 KO mice.Pneumocystisantigen-pulsed BMDCs showed early, but limited, control of infection. Consistent with recent studies that have suggested a role for antigen presentation by B cells, using cells from immunized animals, B cells were able to presentPneumocystisantigens to induce proliferation of T cells. Thus, CD40 expression by B cells appears necessary for robust immunity toPneumocystis.