Liver NKT cells activated by α-GalCer trigger a potent antitumor response mediated via NK cells and subsequently CD8+ T cells8,9. However, NKT cells themselves can cause multiple organ failure, especially in aged mice8,10. On the other hand, NKT cells may play protective roles in some glomerulonephritis or vasculitis models11,12. In a SLE model, the expansion of NKT cells is thought to be involved in the onset of lupus nephritis13, whereas their immunoregulatory roles were also reported both in human SLE and SLE models14–16.