Preparation of reference antisera for laboratory diagnosis of blastomycosis.

Antiserum was prepared in rabbits against the A antigen and a new antigen (labeled the D antigen) of yeast-phase cells of Blastomyces dermatitidis by using immunoelectrophoretic precipitin arcs as vaccine. The antiserum can be used as a reference serum in the immunodiffusion test for identyfying antibodies to the A antigen in sera from patients thought to have blastomycosis. Antibodies to the D antigen have not yet been found in human sera. The rabbit antiserum that was absorbed with Histoplasma capsulatum yeast-phase cells did not react in the complement fixation test with either H. capsulatum yeast-phase or mycelial-phase complement fixation antigen. Therefore, it could also be used as a positive control serum in the complement fixation test. A fluorescent-antibody conjugate prepared from the absorbed serum was found to be valuable for the identification of yeast-phase cells of B. dermatitidis.