Natural killer cell interaction with IgE in the control of ongoing human IgE synthesis

Fresh natural killer (NK) cells from normal donors inhibited IgE synthesis from U266/AF-10 cells via a direct cytolytic effect. This inhibition was 'reversed' by incubation of NK cells with human IgE-anti-IgE immune complexes (IgE-IC) for 16 h without a decrease in NK-mediated cytotoxicity. Upon incubation with IgE-IC, Fc epsilon receptors (FcER) were induced on 3-9% of NK cells. These IgE-IC induced FcER+ NK cells from normal donors secreted (an) IgE-specific factor(s) which enhanced U266/AF-10 IgE production without increasing DNA synthesis. Production of this IgE differentiation factor(s) explains the apparent reversal of NK cell inhibition of IgE production.