Published online Apr 15, 2017. doi: 10.4239/wjd.v8.i4.130
Peer-review started: November 24, 2016
First decision: January 16, 2017
Revised: January 27, 2017
Accepted: February 18, 2017
Article in press: February 20, 2017
Published online: April 15, 2017
Processing time: 141 Days and 12.3 Hours
Natural killer T cells (NKT cells) are innate-like T cells that acquire effector functions while developing in the thymus, polarize into three distinct functional subsets viz. NKT1, NKT2 and NKT17 cells that produce interferon (IFN)-γ, interleukin (IL)-4 and IL-17, respectively. However, there has been no unique surface markers that define each subsets, forcing investigators to use intracellular staining of transcription factors and cytokines in combination of surface markers to distinguish among these subsets. Intracellular staining, however, causes apoptosis and prevents subsequent utilization of NKT cells in functional in vitro and in vivo assays that require viable cells. This limitation has significantly impeded understanding the specific properties of each subset and their interactions with each other. Therefore, there has been fervent efforts to find a specific markers for each NKT cell subset. We have recently identified that syndecan-1 (SDC-1; CD138) as a specific surface marker of NKT17 cells. This discovery now allows visualization of NKT17 in situ and study of their peripheral tissue distribution, characteristics of their TCR and viable sorting for in vitro and in vivo analysis. In addition, it lays the ground working for investigating significance of SDC-1 expression on this particular subset in regulating their roles in host defense and glucose metabolism.
Core tip: Discrete subsets of innate-like Natural killer T (NKT) cells differentially produce three of the most potent and polarizing cytokines, interferon-γ (NKT1), interleukin (IL)-4 (NKT2) and IL-17 (NKT17). But very little is known about how the relationship among the functional subsets of NKT cells is regulated. A major obstacle was the absence of specific single surface markers that reliably identify each subset. Here we highlight our discovery of syndecan-1 as a specific marker of NKT17 subset and its significance for understanding the role of NKT17 in glucose metabolism and autoimmunity.