Abnormalities in cell-mediated immunity in patients with Cryptococcus neoformans infection.

Cryptococcin, streptokinase-streptodornase (SK-SD), mumps, and purified protein derivative (PPD) were used for skin testing and, with whole killed Cryptococcus neoformans, were used in migration inhibition and lymphocyte transformation assays of control subjects and patients with past or present disseminated C. neoformans infection. Cryptococcin was found to differentiate control subjects grouped by known Cryptococcus exposure. Cryptococcin and C. neoformans were effective in stimulating leukocyte migration inhibition and lymphocyte transformation in the cryptococcin skin test-positive control subjects. Fifteen apparently normal patients who had been cured of cryptococcosis were found, as a group, to have impaired responsiveness to skin testing with cryptococcin and mumps, minimal leukocyte migration inhibition when stimulated with cryptococcin or C. neoformans, but normal group responses to cryptococcin in Cryptococcus-induced lymphocyte transformation. Six patients with known predisposing conditions to disseminated infection (sarcoid, lymphoma, leukemia, steroid therapy) had markedly diminished responses to most skin tests and in vitro assays. It is suggested that the apparently normal individual who develops disseminated cryptococcal infection has subtle defects in cellular immunity that may have antedated and predisposed to infection.