Peripheral Blood Invariant Natural Killer T Cells of Pig-Tailed Macaques

In humans, invariant natural killer T (iNKT) cells represent a small but significant population of peripheral blood mononuclear cells (PBMCs) with a high degree of variability. In this study, pursuant to our goal of identifying an appropriate non-human primate model suitable for pre-clinical glycolipid testing, we evaluated the percentage and function of iNKT cells in the peripheral blood of pig-tailed macaques. First, using a human CD1d-tetramer loaded with alpha-GalCer (alpha-GalCer-CD1d- Tet), we found that alpha-GalCer-CD1d-Tet(+)CD3(+) iNKT cells make up 0.13% to 0.4% of pig-tailed macaque PBMCs, which are comparable to the percentage of iNKT cells found in human PBMCs. Second, we observed that a large proportion of V alpha 24(+)CD3(+) cells are alpha-GalCer-CD1d-Tet(+)CD3(+) iNKT cells, which primarily consist of either the CD4(+) or CD8(+) subpopulation. Third, we found that pig-tailed macaque iNKT cells produce IFN-gamma in response to alpha-GalCer, as shown by ELISpot assay and intracellular cytokine staining (ICCS), as well as TNF-alpha, as shown by ICCS, indicating that these iNKT cells are fully functional. Interestingly, the majority of pig-tailed macaque iNKT cells that secrete IFN-gamma are CD8(+) iNKT cells. Based on these findings, we conclude that the pig-tailed macaques exhibit potential as a non-human animal model for the pre-clinical testing of iNKT-stimulating glycolipids.