Factors Influencing Histoplasmin Formation

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Abstract
The effect of various environmental and nutritive factors on the formation of histoplasmin by the mycelium of Histoplasma capsulatum was studied by means of a complement-fixation test. The validity of this complement-fixation test in evaluating the activity of histoplasmin was indicated by the demonstration of a parallelism between the degree of skin reactivity and complement-fixation titer. A maximum yield of histoplasmin in a glucose-asparagine medium was obtained after 8-10 weeks of growth at room temperature. The appearance of histoplasmin in the medium was accompanied by a rise in alkalinity to pH 8-8.5, a drop in reducing sugars to zero and a 25% decrease in total N. When glucose was replaced in the medium by certain polyhexoses (e.g., cellobiose, dextrin, starch or glycogen), appreciably better yields of histoplasmin were obtained.