Identification of antigens and antibodies specific for Pneumocystis carinii

To increase understanding of Pneumocystis carinii and its interaction with its hosts, Ag specific for rodent and human P. carinii were identified by the immunoblot method after PAGE of P. carinii organism extracts. The m.w. of the major Ag of rat P. carinii were 45,000, 110,000, and a broad band of 49,000 to 64,000, and of human P. carinii were 22,000, 24,000, and a broad band of 35,000 to 45,000 daltons. Human and rat pneumocystis were not antigenically identical. Specific antibodies against rat P. carinii Ag were found in 18 of 79 rats by the immunoblot method. Specific antibodies against human P. carinii Ag were found in 32 of 33 adult human sera, but in only 1 of 8 sera from infants and children. Specific antibodies were found in sera of 13 of the 14 adults with no history of P. carinii pneumonia, and all 19 patients with recently diagnosed P. carinii pneumonia, including 9 patients with P. carinii pneumonia associated with AIDS. The results of this study support previous suggestions that a large proportion of adults have been exposed to P. carinii and provide a basis for the further investigations of host-P. carinii interactions.