CD2 is a 50-55 kDa transmembrane glycoprotein expressed on >95% of thymocytes and virtually all peripheral T lymphocytes that serves dual roles in T cell adhesion and activation 1. The mature human CD2 protein consists of 327 amino acids with an extracellular domain of 185 amino acids, a transmembrane region of 24-25 amino acids, and an intracytoplasmic domain of 117 amino acids rich in prolines and basic residues 12. CD2 mediates cell adhesion through interactions with its ligands CD58 (LFA-3) in humans and CD48 in mice, facilitating conjugate formation between T cells and target cells 2. Importantly, cis interactions between CD2 and its ligands on the same T cell are essential for T cell activation and TCR signaling, enabling more robust protein tyrosine phosphorylation 3. CD2 physically associates with components of the TCR complex and the protein tyrosine kinase Lck, and also associates with CD45 phosphatase on T cell surfaces 34. Beyond conventional T cells, CD2 is crucial for MAIT cell maturation and antigen-driven activation 5, and can distinguish functional subsets of plasmacytoid dendritic cells with distinct phenotypes and immunological functions 6. The CD2 gene spans approximately 12 kb on chromosome 1 and consists of five exons 2.