KLRK1 and systemic lupus erythematosus: In this study, SLE patients showed significantly decreased expression of NKG2D on NK (62.58% ± 1.17 vs HC: 92.91% ± 0.50), NKT (56.88% ± 1.08 vs HC: 90.59% ± 0.60) and CD8+ T (59.39% ± 1.13 vs HC: 90.02% ± 0.62) cell subsets, and remarkably increased expression on CD4+ T cell subsets (19.79% ± 1.01 vs 1.70% ± 0.09) (Fig. 1A and B), suggesting the involvement of NKG2D+CD4+ T cells in SLE disease progression.