Galectin-9 Modulates Autoimmunity: Roles in Tissue Inflammation and Organ Involvement.

Galectin-9 (Gal9) is a type of animal lectin that binds terminal β-galactosides and is involved in immunoregulatory functions. Clinically, Gal9 levels are positively correlated with disease activity in systemic autoimmune diseases, and it acts as a modulator of inflammation. Gal9 regulates inflammation and T cell-mediated immune responses, and it can induce apoptosis and autophagy. Intracellularly, Gal9 regulates metabolic signaling pathways and glycosyltransferases. Extracellularly, Gal9 modulates immune polarization and promotes cell-cell interactions by binding to various receptors on immune cells. This review summarizes the multifaceted effects and underlying mechanisms of Gal9 in autoimmune diseases. Given its critical role in tissue inflammation and organ-specific damage in autoimmune diseases, we discuss the current limitations of treatment and the challenges of clinical translation.