Receptors for the Fc fragment of IgG on natural killer cells.

Natural killer (NK) cells are capable of binding to immune-complexed IgG via CD16-Fc gamma RIIIA molecules on their surface. This interaction activates the NK cell lytic mechanism and induces production of lymphokines by the activated cells. The exact molecular basis for CD16-mediated NK cell activation remains unclear; however, a number of recent studies have provided a framework for future research. It has been shown that CD16 perturbation on NK cells evokes a variety of early signal transduction events in these cells, such as polyphosphatidylinositol hydrolysis, [Ca2+]i increases and protein tyrosine kinase activation. Furthermore, the identification, of CD3-zeta/eta and/or Fc epsilon RI-gamma polypeptides complexed with CD16 in NK cells suggests a signal transduction mechanism analogous to those studied for the T cell receptor and Fc epsilon-receptor complexes. Therefore, research on each of these receptor complexes should now be viewed in light of a potential common signal transduction mechanism. Comparison of the similarities and differences observed should yield valuable insight into the complex network of molecular interactions apparently necessary for CD16-mediated NK cell activation.