Surface receptors and immune activity of purified human mononuclear cells. II. The lack of correlation between rosette formation and ADCC cytotoxic activity.

The antibody-dependent cell-mediated cytotoxic (ADCC) activity of normal circulating lymphocytes is limited to those that bear receptors for the FcG of the antibody molecule. The presence of such receptors (FcGR), as detected by the ability of the cells to form rosettes with erythrocytes optimally-sensitized with rabbit IgG antibodies (EA), is not, however, the only reflection of the ADCC activity of these cells: a significant % of circulating lymphocytes can form rosettes with optimally sensitized ox EA (O-EA) indicator cells but cannot mediate ADCC lysis of O-EA. Although the FcGR-bearing lymphocytes form far fewer rosettes with chicken EA (C-EA) indicator cells, they can lyse C-EA very effectively. The O-EA are not resistant to immune lysis since they are totally lysed in the presence of complement. Similarly, circulating lymphocytes form significant numbers of rosettes with human EA but cannot lyse them. A significant % of freshly-isolated T lymphocytes form rosettes with C-EA but cannot lyse them: after incubation at 37 degrees C for 24 h, they can. Incubation T lymphocytes may exhibit a decreased capacity to form rosettes with C-EA indicating a functional loss of FcG receptors, due either to degradation or to decreased accessibility. The relation between the ability of the lymphocytes to rosette with C-EA indicator cells and their ability to lyse them is not simple or direct: this suggests that the capacity to lyse the C-EA depends on interactions other than those occurring between FcGR and the FcG of the target cell-adherent antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)