2 GENES IN THE RAT HOMOLOGOUS TO HUMAN NKG2

Two different lectin-like receptors for MHC class I molecules have so far been identified on natural killer (NK) cells, the Ly-49 homodimeri c receptors in mice and the NKG2/CD94 heterodimeric receptors in human s. The recent identification of a rat CD94 orthologue implied that NK cell receptors equivalent to NKG2/CD94 also exist in rodents. Here we describe the cDNA cloning of two rat genes homologous to members of th e human NKG2 multigene family. The deduced rat NKG2A protein contains a cytoplasmic immunoreceptor tyrosine-based inhibition motif (ITIM), w hereas the cytoplasmic tail of rat NKG2C lacks ITIM. The genes map to the rat NK gene complex and are selectively expressed by NK cells. The expression is strain dependent, with high expression in DA and low in PVG NK cells, correlating with the expression of rat CD94. Ly-49 gene s have previously been identified in the rat, and the existence of rat NKG2 genes in addition to a CD94 orthologue suggests that NK cell pop ulations utilize different C-type lectin receptors for MHC class I mol ecules in parallel.