Application of immunoblotting to detect soluble Pneumocystis carinii antigen(s) in bronchoalveolar lavage of patients with Pneumocystis pneumonia and AIDS.

The technique of immunoblotting for detecting soluble Pneumocystis carinii antigen(s) in bronchoalveolar lavage fluid specimens from patients with AIDS and Pneumocystis pneumonia was evaluated. A soluble 67 kilodalton polypeptide that was immunoreactive with an anti-P carinii monoclonal antibody (2G2) was found in the supernatants of 26 lavage samples from patients with pneumocystosis. Intact organisms in lavage sediments were detected by methenamine silver or immunofluorescence staining procedures. The diagnostic use of this technique was shown in four cases in which lavage sediments proved negative for intact Pneumocystis carinii organisms on first examination; 2G2 reactive soluble antigen, however, was identified in the immunoblots of the supernatants from the same samples. It is concluded that immunoblotting of bronchoalveolar lavage specimens using 2G2 monoclonal antibody as a detection probe may be a useful adjunct to the morphological demonstration of organisms by special staining procedures.