LGALS9

LGALS9 is a human gene that encodes galectin-9, a member of the galectin family of beta-galactoside-binding lectins. Galectin-9 proteins typically contain two carbohydrate recognition domains (N-terminal and C-terminal) joined by a linker peptide. Alternative splicing produces several isoforms with different linker lengths and activities. Galectin-9 binds beta-galactosides and can be secreted or exist in the extracellular matrix.

The gene is expressed in a range of tissues, including immune cells such as dendritic cells and T cells, as well as other tissues. In the immune system, galectin-9 regulates responses by engaging the Tim-3 (HAVCR2) receptor on T cells. Interaction with Tim-3 can promote apoptosis of Th1 and Th17 cells, induce T cell exhaustion, and modulate dendritic cell activity, contributing to immune tolerance and regulation. Galectin-9 also affects natural killer cell activity and B cell functions in some contexts.

In pathological contexts, galectin-9 expression has been associated with tumor immune evasion, chronic infections, and autoimmune disorders. Because of its role in immune modulation, LGALS9 is studied as a potential biomarker and therapeutic target in cancer, infectious disease, and inflammatory conditions.