Isolation of skin test active preparations from yeast phase cells of Blastomyces dermatitidis

Cell wall and cytoplasmic fractions were isolated from mechanically disrupted yeast phase cells of B. dermatitidis in an effort to obtain a reliable skin test antigen. The biological activities of these fractions were compared with those of two blastomycin preparations. The cytoplasmic antigens exhibited a low index of specificity yet exceeded the specificities of the blastomycins. The skin test active component(s) of the cytoplasmic material had a molecular weight between 10,000 and 30,000 and could easily be concentrated by ultrafiltration on a PM-10 membrane. Unlike the cytoplasmic antigens and blastomycins, an alkali soluble, water soluble cell wall antigen effectively distinguished guinea pigs that were sensitized to B. dermatitidis from those sensitized to H. capsulatum. The biological activity of the yeast phase antigen could be quantitated, on a weight basis, after purification by ultrafiltration (PM-10 membrane).