Two dimensional affinity range correlates with phenotypic response to lipid antigens in iNKT cells (IRC4P.600)

Abstract

Abstract Invariant natural killer T cells (iNKT) are a unique group of T cells that possess an invariant T cell receptor (TCR) alpha chain paired with a limited repertoire of TCR beta chains that recognize lipid antigens presented by the MHC-I like molecule, CD1d. The micropipette adhesion frequency assay was used to define 2D affinities of iNKT cells for a panel of lipid:CD1d antigens. Despite having a limited diversity of αβ TCRs, NKT cells possess approximately a 100-fold range of affinities for the lipids tested. Our results show that αGalCer, an INFγ inducing lipid, has an approximately 10-fold higher affinity than OCH, an IL-4 skewing lipid in B6 mice. Moreover, thymic B6 iNKT cells, which predominantly produce Th1 cytokines (IFNγ), possessed a 4-fold higher affinity as compared to iNKT cells from Balb/C mice that favor more of a Th2 (IL-4) response. iNKT cell phenotype is also affected by their location as cells from the liver of Balb/C mice, which are predominantly IFNγ producers have a 2-fold increase in affinity for αGalCer compared to IL-4 predominant thymic iNKT cells. In addition to affinity differences related to phenotype, TCR expression levels of thymic derived iNKT cells reveal that Balb/C mice express twice as much TCR as the B6 mice. Taken together, these results indicate that NKT2 cytokine producing iNKT cells possess lower 2D affinity and higher TCR density compared to their NKT1 producing counterparts.