To gain insight into a possible role for antibody-dependent cell-mediated cytotoxicity in vivo, we examined the ability of leukocytes from 28 patients with primary immunodeficiency and from 20 normal controls to lyse three different types of antibody-coated targets in vitro. Mean cytotoxic indices +/-1 SD elicited by unfractionated mononuclear cells from normal controls were 28.74+/-13.26 for h...