Antibody-dependent leukocyte killing of Cryptococcus neoformans

Cryptococcus neoformans is an encapsulated, yeast-like fungus which is pathogenic for man. The role of various facets of the immune response which prevent disseminated disease in most normal hosts is unclear. A chromium-release assay was developed using radiolabeled cryptococci to reexamine antibody-dependent cell-mediated killing of this fungus. For a small capsule strain this assay served as a qualitative measure of effector cell function and was correlated with an assay of lethal injury to the organism. Polymorphonuclear leukocytes rather than mononuclear cells were the most active effector cells, causing significant chromium release from the fungus at effector-to-target ratios as low as 3:1. Polymorphonuclear leukocytes and mononuclear cells from a patient with chronic granulomatous disease showed minimal antibody-dependent cell-mediated chromium release suggesting that the final fungicidal pathway may be similar in antibody-dependent and antibody-independent leukocyte killing of this organism.