Humoral and cellular immune response in ocular histoplasmosis.

We have compared several humoral and cellular immune responses in ocular and in acute histoplasmosis syndromes. T-lymphocyte subset analysis revealed elevated ratios of T-helper/T-suppressor lymphocytes in ten of 22 patients with ocular histoplasmosis, whereas ratios were depressed in 18 of 22 with acute histoplasmosis syndromes. Lymphocyte transformation responses to mitogens and to histoplasma antigens were similar in both acute and ocular histoplasmosis. However, histoplasma antibody levels as measured by immunodiffusion, complement fixation, and radioimmunoassay were elevated in only three of 22 patients with ocular histoplasmosis, compared with 18 of 22 with acute histoplasmosis. Natural killer cell cytotoxicity was depressed in ten of 20 patients with ocular histoplasmosis compared with none of 18 with acute histoplasmosis. These findings support the clinical observations that ocular histoplasmosis and acute histoplasmosis syndrome are seldom, if ever, seen in the same patient.