Cellular immune activity of a galactomannan protein complex from mycelia of Histoplasma capsulatum

Abstract

A galactomannan protein complex was extracted from defatted mycelium of H. capsulatum with 0.25 N alkali at 25 C. It accounted for 7.5% of the cell dry weight in nondialyzable form and had a galactose mannose ratio of 2:5. The complex containing 68% protein was separated into polysaccharide and glycoprotein components by ion exchange chromatography. The galactomannan formed a single precipitate in immunodiffusion, sharing a common antigen with the glycoprotein which contained two precipitating antigens. The glycoprotein elicited delayed type hypersensitivity in guinea pigs as measured by skin test and macrophage migration inhibitory factor assay, with 5 μg resulting in 86% specific inhibition. The galactomannan was skin test negative, but 10 μg resulted in 80% specific inhibition of migration. (23 references.)