CD4+ T-cell-independent secondary immune responses to Pneumocystis pneumonia

Nicholas M. de la Rua, Derrick R. Samuelson, Tysheena P. Charles, David A. Welsh, Judd E. Shellito

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Pneumocystis pneumonia is a major cause of morbidity and mortality among immunocompromised patients, especially in the context of HIV/AIDS. In the murine model of Pneumocystis pneumonia, CD4+ T-cells are required for clearance of a primary infection of Pneumocystis, but not the memory recall response. We hypothesized that the memory recall response in the absence of CD4+ T-cells is mediated by a robust memory humoral response, CD8+ T-cells, and IgG-mediated phagocytosis by alveolar macrophages. To investigate the role of CD8+ T-cells and alveolar macrophages in the immune memory response to Pneumocystis, mice previously challenged with Pneumocystis were depleted of CD8+ T-cells or alveolar macrophages prior to re-infection. Mice depleted of CD4+ T-cells prior to secondary challenge cleared Pneumocystis infection within 48 h identical to immunocompetent mice during a secondary memory recall response. However, loss of CD8+ T-cells or macrophages prior to the memory recall response significantly impaired Pneumocystis clearance. Specifically, mice depleted of CD8+ T-cells or alveolar macrophages had significantly higher fungal burden in the lungs. Furthermore, loss of alveolar macrophages significantly skewed the lung CD8+ T-cell response toward a terminally differentiated effector memory population and increased the percentage of IFN-γ+ CD8+ T-cells. Finally, Pneumocystis-infected animals produced significantly more bone marrow plasma cells and Pneumocystis-specific IgG significantly increased macrophage-mediated killing of Pneumocystis in vitro. These data suggest that secondary immune memory responses to Pneumocystis are mediated, in part, by CD8+ T-cells, alveolar macrophages, and the production of Pneumocystis-specific IgG.

Original languageEnglish (US)
Article number178
JournalFrontiers in immunology
Issue numberMAY
StatePublished - 2016
Externally publishedYes


  • BMPCs
  • CD8 T-cells
  • Immune memory
  • Macrophages
  • Pneumocystis
  • Pneumonia

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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