Cynomolgus Monkey (Macaca fascicularis) TIM-3 (T cell immunoglobulin and mucin domain-containing protein 3, also known as HAVCR2) is an immune checkpoint receptor that regulates T cell activation, immune tolerance, and inflammatory responses in nonhuman primates. TIM-3 is a member of the TIM (T cell immunoglobulin and mucin domain) family of immune regulatory proteins, which includes TIM-1, TIM-3, and TIM-4, molecules that modulate immune activation and maintain immune homeostasis. In cynomolgus monkeys, TIM-3 is expressed on activated CD4⁺ and CD8⁺ T lymphocytes, natural killer (NK) cells, dendritic cells, and macrophages, where it functions primarily as a negative regulator of immune responses. Interaction of TIM-3 with ligands such as galectin-9, phosphatidylserine, and HMGB1 delivers inhibitory signals that suppress T cell proliferation, cytokine production, and cytotoxic activity, helping prevent excessive immune-mediated tissue damage. Because cynomolgus monkeys are widely used in preclinical infectious disease and immunology research, TIM-3 is frequently studied in models of chronic viral infections (such as SIV/HIV), tuberculosis, and cancer, where increased TIM-3 expression is associated with T cell exhaustion and impaired immune responses. As a key immune checkpoint molecule, cynomolgus monkey TIM-3 is important for studies of immune regulation, host–pathogen interactions, and evaluation of immunotherapies targeting checkpoint pathways, providing translational insight relevant to human disease.