LAG3 and viral infectious disease: In many viral infections, increased expression of inhibitory receptors on exhausted T cells, such as programmed cell death receptor 1 (PD‐1), T‐cell immunoglobulin and mucin‐domain containing‐3 (TIM‐3), cytotoxic T lymphocyte antigen‐4 (CTLA‐4), CD39 (ectonucleoside triphosphate diphosphohydrolase‐1 [ENTPD1]), and lymphocyte activation gene 3 (LAG3) were detected, which resulted in T cell hyporesponsiveness.