Studies of Fungus Antigens: I. Quantitative Studies of Cross-Reactions between Histoplasmin and Blastomycin in Guinea Pigs

Abstract

This is one of a series of papers describing the studies on histoplasmin sensitivity begun at Kansas City in 1945. Six strains of Histoplasma capsulatum and 5 of Blastomyces dermatitidis were used to make histoplasmin and blastomycin by Emmons'' method. Negatively reacting guinea pigs were infected by intraperit. injn. of the yeast phase of the cultures. Tests were made 4-6 weeks after inoculation. A high percentage of animals reacted by skin test to the homologous antigen, but the dilution of antigen required varied with the different lots of antigen. The titer of an antigen is defined as the minimum dosage re- quired to detect sensitivity in 80-90% of the animals. Yeast phase antigens gave approx. the same results as those produced by the Emmons method. Cross reactions were studied in detail. The % of these reactions depends on the particular lot of antigen used and on the antigen dilution. The results do not support Emmons'' claims. When the titers of the antigens are taken into account, the degree of cross reaction between histoplasmin and blastomycin is small. The antigens are therefore relatively specific for infections with the homologous fungi.