Serologic responses to Pneumocystis carinii antigens in health and disease

Serum antibodies to human Pneumocystis carinii antigens were measured in >400 specimens from different population groups by the immunoblotting technique. Serologic responses varied during the first 2 years of life, but in children ≥27#x00BD; years and in adults antibodies to a 4D-kDa band were found in >85% of the specimens; antigens to bands of 66,92, and 116kDa were also detected frequently. The prevalence of serum antibodies in immunosuppressed patients varied at different institutions and was usually lower than that of healthy controls. Seven (41%) of 17 patients with single episodes of pneumocystosis and 13 (93%) of 14 patients with recurrent episodes followed sequentially developed active serum IgM and/or IgG antibody responses to the 4D-kDa antigen. Serologic responses to P. carinii were also detected, though less frequently, by immunofluorescence. These data suggest that the 4o-kDa antigen is a major marker of P. carinii infection and that immunoblotting is useful in measuring serum antibody responses to the organism in both normal and immunocompromised hosts.