HUMAN NATURAL-KILLER (NK) ALLOREACTIVITY AND ITS ASSOCIATION WITH THEMAJOR HISTOCOMPATIBILITY COMPLEX - ANCESTRAL HAPLOTYPES ENCODE PARTICULAR NK-DEFINED HAPLOTYPES

As ancestral haplotypes of the major histocompatibility complex (MHC) appear to define identical MHC haplotypes in unrelated individuals, un related individuals sharing the same ancestral haplotype should also s hare the same NK-defined allospecificities that have recently been sho wn to map to the human MHC. To test this prediction, multiple cell lin es from unrelated individuals sharing the same ancestral haplotypes we re tested for the NK-defined allospecificities. It was found that cell s sharing the same ancestral haplotypes do have the same NK-defined sp ecificities. Furthermore, the NK-defined phenotype of cells that posse ss two different ancestral haplotypes can be predicted from the NK-def ined phenotypes of unrelated cells that are homozygous for the ancestr al haplotypes concerned. Although the group 1 and 2 NK-defined allospe cificities can be explained to some extent by HLA-C alleles, evidence is presented that additional genes may modify the phenotype conferred by HLA-C.