NK cell recognition of major histocompatibility complex class I molecules.

Interactions between membrane receptors on NK cells and major histocompatibility complex (MHC) class I molecules on target cells inhibit NK cell-mediated cytotoxicity. In the mouse, receptors encoded by genes of the Ly-49 family bind certain polymorphic H-2 molecules and prevent lysis of normal hematopoietic cell targets. While a human homolog of Ly-49 has not been identified as yet, two structurally distinct NK cell-associated membrane glycoproteins, NKB1 and p58, have been implicated in the recognition of polymorphic HLA-B and HLA-C molecules, respectively. Recent studies indicate that human NK cell clones express multiple receptors for HLA class I molecules and suggest that these receptors may operate independently when expressed in a single NK cell clone.