PDCD1 and systemic lupus erythematosus: To further assess the expression of costimulatory molecules on T cell subsets, we investigated the expression of PD-1, TIM-3, and TIGIT on T cells and showed that the frequencies of PD-1 or TIM-3-expressing CD3+CD4+ T cells or CD3+CD8+ T cells were significantly increased in those SLE patients with positive anti-dsDNA antibodies compared with the HC.