Galectin-9 is a secreted carbohydrate-binding protein with two lectin domains connected by a linker region. Progressive deletion within the linker region generates an isoform known as Ecalectin or UAT. Galectin-9 binds to carbohydrate moieties of IgE, preventing immune complex formation, mast cell degranulation, and asthmatic and cutaneous anaphylaxis reactions. It functions as an eosinophil chemoattractant and induces the maturation of dendritic cells which promote Th1 polarization. Galectin-9 binds to TIM-3, inhibiting Th1 cell and CD8+ T cell responses but promoting Treg differentiation and activity. Galectin-9 suppresses tumor cell metastasis by interfering with the associations between hyaluronic acid and CD44 and between VCAM-1 and Integrin alpha4 beta1. The Ecalectin isoform (UAT; urate transporter) can be expressed as an integral membrane protein and mediate the cellular efflux of urate.