PNEUMOCYSTIS-CARINII INFECTION IN TRANSGENIC B-CELL-DEFICIENT MICE

Pneumocystis carinii is an important cause of pneumonia in immunocompr omised hosts, Both cellular and humoral immunity seem important in res istance to this pathogen, but the specific role of each component is p oorly understood. An outbreak of P. carinii pneumonia in transgenic B cell-deficient mice (mu MT) was studied. Over 4 months, >50% of 41 mu MT/mu MT mice maintained in a sterile environment died of pneumonia. S ome mice had concurrent infection with Pasteurella pneumotropica. Homo zygous mu MT/mu MT mice had no detectable serum immunoglobulins, while their heterozygous mu MT/+ counterparts had normal levels of IgM, IgG , and IgA and did not develop pneumonia, The infection was controlled by treating the mice with trimethoprim-sulfamethoxazole, and the patho gen was eliminated by cesarean rederivation, These observations sugges t an important role for B cells in the host defense against P. carinii .