Clearance of Pneumocystis carinii in mice is dependent on B cells but not on P. carinii-specific antibody

Frances E. Lund, Kevin Schuer, Melissa Hollifield, Troy D. Randall, Beth A. Garvy

Research output: Contribution to journalArticlepeer-review

88 Scopus citations


Both CD4+ T cells and B cells are critical for defense against Pneumocystis carinii infection; however, the mechanism by which B cells mediate protection is unknown. We show that P. carinii-specific IgM is not sufficient to mediate clearance of P. carinii from the lungs since CD40-deficient mice produced normal levels of specific IgM, but were unable to clear the organisms. Using chimeric mice in which the B cells were deficient in CD40 (CD40KO chimeras) we found that clearance of P. carinii infection is delayed compared with wild-type controls. These CD40KO chimeric mice produced normal levels of P. carinii-specific IgM, but did not produce class-switched IgG or IgA. Similarly, clearance of P. carinii was delayed in mice deficient in FcγRI and III (FcγRKO), indicating that P. carinii-specific IgG partially mediates opsonization and clearance of P. carinii. Opsonization of organisms by complement did not compensate for the lack of specific IgG or FcγR, since C3-deficient and C3-depleted FcγRKO mice were still able to clear P. carinii. Finally, μMT and CD40KO chimeric mice had reduced numbers of activated CD4+ T cells in the lungs and lymph nodes compared with wild-type mice, suggesting that B cells are important for activation of T cells in response to P. carinii. Together these data indicate that P. carinii-specific IgG plays an important, but not critical, role in defense against P. carinii. Moreover, these data suggest that B cells also mediate host defense against P. carinii by facilitating CD4+ T cell activation or expansion.

Original languageEnglish
Pages (from-to)1423-1430
Number of pages8
JournalJournal of Immunology
Issue number3
StatePublished - Aug 1 2003

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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