Poster Presentation Australasian Society for Immunology Annual Scientific Meeting 2014

Natural killer T cells are a distinct subset of T lymphocytes. They express both T cell receptors and some markers typical of natural killer cells. NKT cells originate from the same progenitors as conventional T cells. They branch off from common precursors at the CD4⁺CD8⁺ (DP) stage after the random rearrangement of their TCR genes and selection by CD1d. However, all mouse strains produce very low numbers of DP NKT cells, and this subset has not been well characterized. To overcome this problem as well as to show this subset, we had produced NOD mice transgenic for Va14-Ja18 (NOD.Va14tg). These mice have large numbers of DP NKT cells. Knock-out of the CD1d gene in NOD.Va14tg mice increased the very immature DP NKT cell population in the thymus and almost eliminated them in the spleen and liver. Additionally, iv. injection of a-GalCer diminished the DP NKT cells in the thymus of NOD.Va14tg mice (compared to NOD.CD1d^-/-.Va14tg mice or controls injected with vehicle). FACS sorted thymic immature DP NKT cells (CD4⁺CD8⁺CD24^highNK1.1^-CD1d-tet⁺TCRb⁺ cells), immature DP conventional T cells (CD4⁺CD8⁺CD24^highNK1.1^-CD1d-tet^-TCRb⁺ cells) and post-selection immature CD4⁺ NKT cells (CD4⁺CD8^-CD24^highNK1.1^-CD1d-tet⁺TCRb⁺ cells) were subjected to gene expressional comparison by micro arrays. Transcriptional analyses revealed that of the 44 genes identified as being up-regulated by positive selection, only 3 were expressed at higher levels in immature DP NKT cells than in immature DP conventional T cells.  In contrast, many of these genes were up-regulated during the transition from immature DP NKT cells to the immature CD4⁺ NKT cells. These results suggest that our NOD.Va14tg mice produced the earliest progenitor of NKT cells, which enables us to dissect NKT cell differentiation from the DP stage onwards.