PDCD1 and infection: In a recent study, Tregs derived IL-35 promoted the expression of CD4+ Tconv, CD8+ T cells and B lymphocytes inhibitory receptor, such as programmed cell death protein 1 (PD-1), T cell immunoglobulin and mucin domain 3 (TIM-3), cytotoxic T Lymphocyte-associated antigen-4 (CTLA-4) and lymphocyte activation gene 3 (LAG-3), which played important roles in the tolerance of infection (Sullivan et al., 2020).