Bovine TIM-3 (T cell immunoglobulin and mucin domain-containing protein 3, also known as HAVCR2, hepatitis A virus cellular receptor 2) is an immune checkpoint receptor that regulates T cell activation, immune tolerance, and inflammatory responses in cattle (Bos taurus). 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 help control immune activation and maintain immune homeostasis. In cattle, TIM-3 is expressed on activated T lymphocytes, natural killer (NK) cells, dendritic cells, and macrophages, where it functions primarily as a negative regulator of immune responses. Engagement of TIM-3 with its ligands—such as galectin-9, phosphatidylserine, and HMGB1—delivers inhibitory signals that suppress T cell proliferation, cytokine production, and cytotoxic activity, thereby preventing excessive immune-mediated tissue damage. In bovine health, TIM-3 signaling has been associated with immune regulation during chronic infectious diseases, including bovine leukemia virus (BLV) infection, bovine tuberculosis caused by Mycobacterium bovis, and other persistent infections, where increased expression of immune checkpoint receptors can contribute to T cell exhaustion and reduced pathogen clearance. Because immune checkpoint pathways strongly influence host immunity and pathogen persistence, bovine TIM-3 is an important target of study in veterinary immunology, chronic infection research, and development of immunomodulatory strategies aimed at improving immune responses and disease resistance in cattle.