CD4 and neoplasm: LAG-3 negatively modulates T cell proliferation, activation and homeostasis36 and has similar functions to CTLA-4 and PD-1.37 LAG-3 plays a vital role in the inhibitory function of Tregs.38 In some malignancies, the coexpression of LAG-3 and PD-1 on tumour-infiltrating lymphocytes is related to the impaired function of CD8+ effector T cells, which promotes the immune escape of tumours.39 LAG-3 has a similar protein sequence to the CD4 receptor.