REGULATION OF ADAPTIVE IMMUNITY BY NATURAL-KILLER-CELLS

Natural killer (NK) cells are well recognized as cytolytic effector ce lls of the innate immune system. In the past several years, the struct ure and function of NK cell receptors for the major histocompatibility complex (MHC) class I molecules and other ligands have been the subje ct of extensive studies. These studies have focused largely on the mec hanisms of target cell recognition for lysis. Another aspect of NK cel l function that seems to be underappreciated is their role in immune r egulation. Since NK cells produce a number of immunologically relevant cytokines, it has been suggested that these cells may modulate the de velopment of the adaptive immune response. But, is it the only mechani sm by which NK cells interact with cells involved in the induction of antigen-specific responses? This article reviews some older and more r ecent studies and attempts to place NK cells in the context of potent immune regulators of T cell responses.