Phylogeny of NK cell reactivity against human and nonhuman primate lymphoblastoid cell lines: evolving and conserved target antigens.

Both human and nonhuman primate natural killer (NK) cells display little or no killing against allogeneic B lymphoblastoid cell lines. However, the same B cell lines are killed in baboon-human (B alpha H) or human-baboon (H alpha B) xenogeneic combinations. Competition-inhibition experiments indicate that the xenogeneic determinants recognized by NK cells are found principally if not exclusively on B rather than T target cells. Cell lines from closely related chimpanzee or orang-utan species can block some killing of human target cells, but lines from more distantly related species including gibbon, macaque, baboon, and marmoset do not inhibit cytotoxicity. This suggests that some NK target structures are susceptible to evolutionary change. Gibbon or marmoset lines infected with Epstein Barr virus (EBV) do not block killing, suggesting that host rather than viral determinants are being recognized. In contrast to the foregoing pattern, 2 cell lines derived from the same baboon differed in susceptibility to NK lysis irrespective of the effector cell species. The viral producer line 13CB-1 was more susceptible to lysis than its viral nonproducer partner 26CB-1. Thus, some NK target antigens may be highly conserved whereas others evolve with the species.