Serology of pneumocystosis.

Included in this evaluation of serologic tests for American pneumocystis pneumonia is a summary of results reported from an indirect immunofluorescence (IF) test and a comparison of results of the immunodiffusion, complement-fixation, and double diffusion tests. Athough IF was the most sensitive, it dectected only a third of the infections. Specificity of the test was good when serum titers greater than or equal to 1:16 were considered postive. Results of test sera in both European and American laboratories suggested that the low level of measurable antibody in American sera real and not due to technical error. These findings are compatible with the concept that two types of population may be infected with Pneumocystis organisms, one type associated with plasma cell pneumonia and the second with hypoergic pneumocystosis in immunosuppressed patients. Analysis by double diffusion to test antigens revealed their antigenic complexity. Most components, were indentified or partially identified with host elements, and no purely parastic antigens were demonstrated. When cysts isolated from animals and humans were tested, results suggested that they shared at least some common antigens.