PDCD1 and systemic lupus erythematosus: The frequencies of TIM-3+PD-1− and TIM-3+PD-1+NK cells in SLE patients were significantly increased compared with that in the HC (both P < 0.05) (Fig. 2b, c), whereas the frequency of TIM-3−PD-1+ NK cells did not show any significant differences between the SLE patients and HC (P > 0.05) (Fig. 2d).