T-lymphocyte surface antigen Ly-9 (LY9)

SLAM receptors triggered by homo- or heterotypic cell-cell interactions are regulating the activation and differentiation of a wide variety of immune cells and are involved in the regulation and interconnection of both innate and adaptive immune reaction. Activities are controlled by presence or absence of small cytoplasmic adapter proteins, SH2D1A/SAP and/or SH2D1B/EAT-2.

May participate in adhesion reactions between T lymphocytes and accessory cells by homophilic interaction. Promotes T-cell differentiation into a helper T-cell Th17 phenotype leading to greater IL-17 secretion; the costimulatory activity demands SH2D1A (PubMed:22184727).