Conservation of molecular and cellular phenotypes of invariant NKT cells between humans and non-human primates

Invariant NKT (iNKT) cells in both humans and non-human primatesare activated by the glycolipid antigen, α- galactosylceramide(α-GalCer). However, the extent to which the molecular mechanisms of antigen recognitionand in vivo phenotypes of iNKT cells are conserved among primatespecies has not been determined. Using an evolutionary genetic approach, we found a lack of diversifying selection in CD1genes over 45 million years of evolution, which stands in stark contrast to the history of the MHC system for presenting peptide antigens to T cells. The invariant T cell receptor (TCR)-α chain was strictly conserved across all seven primateclades. Invariant NKT cells from rhesus macaques(Macaca mulatta) bind human CD1D-α-GalCer tetramerand are activated by α-GalCer-loaded human CD1Dtransfectants. The dominant TCR-β chain cloned from a rhesus-derived iNKT cell line is nearly identical to that found in the human iNKT TCR, and transduction of the rhesus iNKT TCR into human Jurkat cellsshow that it is sufficient for binding human CD1D-α-GalCer tetramer. Finally, we used a 20-color flow cytometry panel to probe tissue phenotypes of iNKT cells in a cohort of rhesus macaques. We discovered several tissue-resident iNKT populations that have not been previously described in non-human primatesbut are known in humans, such as TCR-γδ iNKTs. These data reveal a diversity of iNKT cell phenotypes despite convergent evolutionof the genes required for lipid antigen presentation and recognition in humans and non-human primates.