Marginal Zone B Cells Regulate Antigen-Specific T Cell Responses during Infection

Marginal zone B cells (MZB) participate in the early immune response to several pathogens. In this study, we show that in mu MT mice infected with Leishmania donovani, CD8 T cells displayed a greater cytotoxic potential and generated more effector memory cells compared with infected wild type mice. The frequency of parasite-specific, IFN-gamma(+) CD4 T cells was also increased in mu MT mice. B cells were able to capture parasites, which was associated with upregulation of surface IgM and MyD88-dependent IL-10 production. Moreover, MZB presented parasite Ags to CD4 T cells in vitro. Depletion of MZB also enhanced T cell responses and led to a decrease in the parasite burden but did not alter the generation of effector memory T cells. Thus, MZB appear to suppress protective T cell responses during the early stages of L. donovani infection. The Journal of Immunology, 2012, 188: 3961-3971.