T cells are not sufficient for resistance to Pneumocystis carinii pneumonia in mice.

Severe combined immunodeficient (SCID) mice given spleen cells from immunocompetent donors resolve their pre-existing Pneumocystis carinii pneumonia (PCP). However, SCID mice given infusions of thymus cells or spleen cells depleted of cells positive for either immunoglobulin or immune response-associated antigen did not resolve their PCP. Immunofluorescence staining and mitogen responses of spleen cells from the recipient SCID mice confirmed that all groups of mice contained functional T cells but only the mice, reconstituted with nondepleted spleen cells, contained B cells. These results indicate, that T cells alone are not sufficient to resolve PCP in SCID mice and that B cells probably must also be present.