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. 2014 Oct 28;5:543. doi: 10.3389/fimmu.2014.00543

Figure 1.

Figure 1

NKT cell subsets. The natural killer T (NKT) cell population encompasses several phenotypically and functionally different subpopulations. Tissue location and surface markers (CD4, CD8, and NK1.1) are defining characteristics that broadly divide NKT cells and contribute to functionality. Differences in TCR rearrangements allow separation into two major subsets, type I and type II. Type I NKT cells express a semi-invariant TCRα chain, while type II NKT cells display a more diverse repertoire. It has been proposed that these NKT cell subsets recognize distinct lipid antigens. The prototypic antigen able to activate all type I NKT cells is α-GalCer. Type II NKT cells recognize a greater variety of antigens, one being sulfatide. Though these two subsets have been reported to recognize some common antigens, e.g., β-GlcCer, the biochemical structure is slightly different between the antigen recognized by type I versus type II NKT cells. Lastly, type I NKT cells are functionally heterogeneous. NKT1, NKT2, NKT17, NKTreg, NKTFH, and NKT10 subsets have been described. Overall, an in vivo NKT cell response likely depends on which subsets are activated.