Abstract: 　Objective] To define the cell populations contributing to inflammation-associated respiratory impairment in Pneumocystis carinii pneumonia (PCP). [Methods] The host inflammation response was observed in CD4 +T cell-depleted mice and in CD4 + and CD8 + T cell-depleted mice infected with P carinii via intratracheal inoculation. [Results] Mice depleted of both CD4 + and CD8 + T cells developed infection with neither increased respiratory rate nor lung injury. In contrast, mice depleted of CD4 + T cells alone exhibited severe pulmonary inflammation, and increased respiratory rates. Respiratory compromise was associated with the presence of activated CD8 + cells and neutrophils in the BALF. [Conclusion] The host′s inflammatory cell response to P. carinii directly impairs pulmonary function and contributes to the pathogenesis of PCP, CD8 + T cells appear to play a major role.

Key words: PCP, Inflammation, CD8 + T cells, CD4 + T cells