KLRK1 and systemic lupus erythematosus: Similar results were obtained as in SLE patients, which showed NKG2D+CD4+ T cells frequency is inversely correlated to the frequency of CD4+ T cells (R2 = 0.3830, P = 0.0139) and Treg cells (R2 = 0.6089, P = 0.0006), respectively (Fig. 2C).