B cells play a critical role in the clearance of Pneumocystis. In addition to production of Pneumocystis-specific Abs, B cells are required during the priming phase for CD4+ T cells to expand normally and generate memory. Clearance of Pneumocystis was found to be dependent on Ag specific B cells and on the ability of B cells to secrete Pneumocystis-specific Ab, as mice with B cells defective in these functions or with a restricted BCR were unable to control Pneumocystis infection. Because Pneumocystis-specific antiserum was only able to partially protect B cell–deficient mice from infection, we hypothesized that optimal T cell priming requires fully functional B cells. Using adoptive transfer and B cell depletion strategies, we determined that optimal priming of CD4+ T cells requires B cells during the first 2–3 d of infection and that this was independent of the production of Ab. T cells that were removed from Pneumocystis-infected mice during the priming phase were fully functional and able to clear Pneumocystis infection upon adoptive transfer into Rag1−/− hosts, but this effect was ablated in mice that lacked fully functional B cells. Our results indicate that T cell priming requires a complete environment of Ag presentation and activation signals to become fully functional in this model of Pneumocystis infection.
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This work was supported by National Institutes of Health/National Heart, Lung, and Blood Institute Grant HL088989 (to B.A.G.).
The online version of this article contains supplemental material.
Opata, Michael M.; Hollifield, Melissa L.; Lund, Frances E.; Randall, Troy D.; Dunn, Robert; Garvy, Beth A.; and Feola, David J., "B Lymphocytes Are Required during the Early Priming of CD4+ T Cells for Clearance of Pneumocystis Infection in Mice" (2015). Microbiology, Immunology, and Molecular Genetics Faculty Publications. 145.