IL-10-producing B cells regulate Th1/Th17-cell immune responses in Pneumocystis pneumonia

Pneumocystis pneumonia (PCP) is a common opportunistic infectious disease that is prevalent in immunosuppressed hosts. Accumulating evidence shows that B cells play an important role in infectious diseases. In the present study, the immune regulatory role of mature B cells in host defense to Pneumocystis was evaluated. Pneumocystis infection resulted in a decrease in B cells in patients and mice, and the Pneumocystis burden in B cell-deficient (μMT) mice also progressively increased from weeks 1 to 7 after infection. The clearance of Pneumocystis was delayed in BAFF-R-deficient mice (BAFF-R‒/‒ mice), which had few B cells and Pneumocystis-specific IgG and IgM antibodies, compared with clearance in wild-type (WT) mice. There were fewer effector CD4+ T cells and higher percentages of Th1/Th17 cells in BAFF-R‒/‒ mice than in WT mice. Adoptive transfer of naive B cells, mRNA sequencing, and IL-1β neutralization experiments indicated that IL-1β is a likely determinant of the B10 cell-mediated suppression of Th...