PDCD1 and systemic lupus erythematosus: The comparison of active versus inactive SLE patients and active SLE patients versus HC showed no significant difference regarding the percentages of IFN-γ-producing PD-1+CD4+ T-cells (38.0 ± 20.9% vs. 30.4 ± 14.3%; p = 0.40 and 38.0 ± 20.9% vs. 41.8 ± 14.3%; p = 0.75, respectively).