RAET1/ULBP alleles and haplotypes among Kolla South American Indians

NK cell cytolysis of infected or transformed cells can be mediated by engagement of the activating immunoreceptor NKG2D with one of eight known ligands (MICA, MICB and RAET1E-N) and is essential for innate immunity. As well as diversity of NKG2D ligands having the same function, allelic polymorphism and ethnic diversity has been reported. We previously determined HLA class I allele and haplotype frequencies in Kolla South American Indians who inhabit the northwest provinces of Argentina, and were found to have a similar restricted allelic profile to other South American Indians and novel alleles not seen in other tribes. In our current study, we characterized retinoic acid early transcription-1 (RAET1) alleles by sequencing 58 unrelated Kolla people. Only three of six RAET1 ligands were polymorphic. RAET1E was most polymorphic with five alleles in the Kolla including an allele we previously described, RAET1E*009 (allele frequency (AF) 5.2%). Four alleles of RAET1L were also found and RAET1E*002 was most frequent (AF=78%). Potential functional diversity only affected RAET1E and RAET1L, which were in linkage disequilibrium indicating a selective advantage. The results suggest that limited RAET1 polymorphism in the Kolla was not detrimental to human survival but still necessary and may affect disease susceptibility or severity.