T-lymphocyte surface antigen Ly-9 (LY9)

T-lymphocyte surface antigen Ly-9 (LY9, CD229, SLAMF3) is a membrane receptor belonging to the SLAM family of immunomodulatory receptors. It is predominantly expressed on T lymphocytes, natural killer (NK) cells, and other immune cells[1][2][3][7]. LY9 mediates cell-cell interactions mainly via homophilic binding, modulates immune responses by acting as a self-ligand receptor, and interacts with the adaptor protein SAP (SH2D1A). It is crucial for T-cell activation, differentiation (especially into Th17 helper T cells), and serves regulatory roles in both adaptive and innate immunity—negatively regulating T-cell and invariant NKT cell development and function[1][2][3][7]. Dysregulation or mutation of LY9 is linked to several immune-related diseases including immunodeficiencies and autoimmune disorders[1][3]. Currently, there are no approved drugs directly targeting LY9, but its role as an immune modulator makes it a potential target for therapeutic intervention.

Other names

CD229SLAM family member 3SLAMF3Cell surface molecule Ly-9Lymphocyte antigen 9hly9mLY9T-lymphocyte surface antigen Ly-9Signaling lymphocytic activation molecule 3