CD4 and neoplasm: The immune checkpoint receptor lymphocyte-activation gene 3 (LAG-3) is an activation marker for CD4+ and CD8+ T cells and other lymphocytes.11-14 As observed with other immune-modulating receptors, such as PD-1, prolonged expression of LAG-3 negatively regulates T-cell activation and function, leading to T-cell exhaustion and tumor immune escape.11-13,15 Therefore, blockade of LAG-3 in the tumor microenvironment may restore antitumor immune response.