Monoclonal antibodies against the NK cell-FcR and the T3-complex potentiate normal lymphocyte killing

Pretreatment of normal human lymphocytes with monoclonal IgG against the NK cell-FcR (IgG) or the T3 complex was found to potentiate killing of most NK sensitive target cells with the exception of T-cell derived cells. Anti-FcR IgM monoclonals were suppressive for all target cells. IgG anti-FcR mediated potentiation required minute amounts of antibody but was also seen at high anti-FcR concentrations that modulated FcR activity. Potentiated and FcR modulated cells retained anti-FcR IgG on the membrane and conjugated normally to target cells. Anti-FcR potentiation blocked antibody-dependent killing but did not influence lectin-dependent killing, with anti-T3 the opposed effect was seen. Combined anti-FcR and anti-T3 treatment resulted in decreased potentiation. The results suggest that the NK cell-FcR may be activated during normal NK cell killing (without the addition of antibody) as suggested for FcR in B cell triggering.