Precipitation reaction in agar in North American blastomycosis.

Abstract

Abstract With the use of the technique of double diffusion in agar, serum precipitins to Blastomyces dermatitidis antigens were demonstrated in fourteen of twentytwo patients with North American blastomycosis. In some patients no precipitins could be demonstrated after therapy, while in others precipitins were present although there was no apparent active infection. Correlation with complement fixation reactions was generally good; however, discordant results were observed in four individuals. Precipitin reactions with heterologous fungal antigens occurred in only four patients and all contained a Histoplasma capsulatum antigen important in eliciting dermal hypersensitivity in histoplasmosis. It is likely that these precipitins were stimulated by prior skin testing with histoplasmin in individuals with previously acquired but healed histoplasmosis and that they had no relation to the blastomycosis. Precipitins to blastomyces antigens were also found in the sera of some patients with histoplasmosis and coccidioidomycosis. Such precipitins could readily be shown to be cross-reacting antibodies stimulated by antigens common to Blastomyces dermatitidis, Histoplasma capsulatum, and Coccidioides immitis and were easily distinguishable from the specific antibodies found in blastomycosis. Because this technique allowed the demonstration of specific blastomyces antibodies, it was helpful in clarifying confusing complementfixation tests, which in these patients gave cross-reactions with histoplasma antigens.