BINDING OF A SOLUBLE P70 KILLER-CELL INHIBITORY RECEPTOR TO HLA-B-ASTERISK-5101 - REQUIREMENT FOR ALL 3 P70 IMMUNOGLOBULIN DOMAINS

Lysis of target cells by natural killer (NK) cells can be prevented by killer cell inhibitory receptors (KIR) specific for major histocompat ibility complex class I molecules. Functional studies have identified two distinct p58 KIR, each reactive with a different group of HLA-C al lotypes, and distinct p70 KIR specific for some HLA-B or HLA-A allotyp es. The NK specificities for each group of HLA-C allotypes have been r eproduced by direct binding of recombinant soluble p58 molecules. Here , we show that a soluble p70 KIR binds to HLA-B5101, but not to HLA-A or HLA-C molecules. Truncated soluble forms of the HLA-B5101-specifi c p70 KIR, including one with two immunoglobulin (Ig) domains reactive with a monoclonal antibody that blocks p70 KIR function, did not bind to HLA-B5101, indicating that all three Ig domains are required for binding.