CRTAM (cytotoxic and regulatory T cell molecule) is a nectin-like adhesion molecule that mediates heterophilic cell-cell interactions critical for T cell and NK cell function. CRTAM is rapidly induced upon lymphocyte activation through AP-1 transcription factor signaling 1 and interacts with nectin-like ligands to regulate immune responses. Engagement of CRTAM with its ligand CADM1 promotes NK cell cytotoxicity and IFN-γ secretion by CD8+ T cells, enhancing tumor rejection 2. CRTAM expression is essential for CD4+ cytotoxic T lymphocyte (CTL) differentiation, driving expression of CTL-related genes including granzyme B and perforin 3. Functionally, CRTAM regulates CD8+ T cell proliferation following TCR activation and facilitates intestinal retention of intraepithelial T cells through interaction with CD103+ dendritic cells 2. In cancer immunotherapy, elevated CRTAM expression in triple-negative breast cancer correlates with favorable survival and enhanced CD8+ T cell infiltration 4. Clinically, CRTAM emerges as a biomarker: its downregulation in vitiligo lesions with JAK3 inhibitor treatment correlates with clinical improvement 5, while altered CRTAM expression in inflammatory arthritis and Crohn's disease associates with disease pathogenesis 67. Persistent CRTAM+ cytotoxic T cells in resolved atopic dermatitis suggest disease memory and potential relapse mechanisms 8.