Detection of Autoreactive Type II NKT Cells: A Pilot Study of Comparison Between Healthy Individuals and Patients with Vasculitis

NKT cells are defined as T cells that recognize hydrophobic antigens presented by class I MHC‐like molecules, including CD1d. Among CD1d‐restricted NKT cells, type I and type II subsets have been noted. CD1d‐restricted type I NKT cells are regarded as pro‐inflammatory cells in general. On the contrary, accumulated evidence has demonstrated an anti‐inflammatory property of CD1d‐restricted type II NKT cells. In our earlier study using a rat model with vasculitis, we demonstrated the pro‐inflammatory function of CD1d‐restricted type II NKT cells and identified that one such cell recognized P518–532 of rat sterol carrier protein 2 (rSCP2518–532), which appeared on vascular endothelial cells presented by CD1d. Based on this evidence, we attempted to detect human CD1d‐restricted type II NKT cells in peripheral blood using hSCP2518–532, the human counterpart of rSCP2518–532, together with a CD1d tetramer in flow cytometry. First, we determined the binding of hSCP2518–532 to CD1d. Next, we detected CD3‐positive hSCP2518–532‐loaded CD1d (hSCP2518–532/CD1d) tetramer‐binding cells in peripheral blood of healthy donors. The abundance of TGF‐β‐producing cells rather than TNF‐α‐producing cells in CD3‐positive hSCP2518–532/CD1d tetramer‐binding cells suggests the anti‐inflammatory property of SCP2‐loaded CD1d (SCP2/CD1d) tetramer‐binding type II NKT cells in healthy individuals. Furthermore, we compared cytokine profile between healthy individuals and patients with vasculitis in a pilot study. Interestingly, the percentage of TGF‐β‐producing cells in SCP2/CD1d tetramer‐binding type II NKT cells in vasculitic patients was significantly lower than that in healthy controls despite the greater number of these cells. Although further studies to clarify the mechanism and significance of this phenomenon are needed, SCP2/CD1d tetramer‐binding type II NKT cells in peripheral blood should be examined in more detail to understand the pathophysiology of vasculitides in humans. © 2018 International Society for Advancement of Cytometry