Diagnosis of histoplasmosis and blastomycosis by an antiglobulin hemagglutination test

An antiglobulin hemagglutination test was developed for detection of antibody directed to Histoplasma capsulatum and Blastomyces dermatitidis. The substances responsible for spontaneous agglutination of erythrocytes were removed from histoplasmin and blastomycin by vacuum dialysis, and partial purification of the antigens by gel filtration chromatography on Sephadex G-150 allowed removal of additional nonantigenic material which competed with the antigens for binding on the erythrocyte surface. The test was sensitive enough to detect antibodies in sera which were negative by complement fixation, immunodiffusion, or both, but it failed to discriminate reliably between antibody directed to H capsulatum and antibody directed to B dermatitidis. Erythrocytes sensitized with partially purified blastomycin produced some false-positive reactions with normal canine sera; this was corrected by diluting the antigen before sensitization of the erythrocytes.