Cell-mediated cytotoxicity. Characterization of the effector cells.

Isolated human mononuclear cells were fractionated according to their membrane characteristics or physical properties. Adherent cells were depleted by filtration through glass columns; phagocytic cells were removed by iron treatment and cell subpopulations capable of forming rosettes with sheep erythrocytes (E), erythrocyte-antibody-complement (EAC) and chicken erythrocyte-antibody complexes (CEA) were separated by centrifugation of Ficoll-Hypaque gradients. The functional activity of the cell subpopulations obtained was assayed by testing PHA-induced cytoxicity (PIC), antibody-dependent cytoxicity (ADCC) and blast transformation by PHA. The results of this study demonstrate that: (1) cells reacting in PIC and ADCC assays are different, adherent and phagocytic cells being necessary for full expression of PIC and not for ADCC; (2) PHA induces direct blast transformation of purified E-RFC in the absence of PIC cytotoxic cells; (3) cell populations specifically enriched in E or EAC rosette-forming cells are not cytotoxic neither in the PHA nor in antibody mediated cytotoxic assays; (4) cells participating in ADCC can be selectively purified by centrifugation of CEA rosettes.