The function of co-inhibitory receptors, including Tim-3, programmed death-1 (PD-1), cytotoxic T lymphocyte antigen-4 (CTLA-4), and lymphocyte-activation gene 3 (LAG-3), are critical for lymphocyte homeostasis prompting it a novel target for treatment in tumor and infection (43, 44). This evidence concerns the gene CTLA4 and infection.