The RG9-1 monoclonal antibody reacts with mouse galectin-9 a 40 kDa S-type lectin that is expressed by various cell types including lymphocytes, thymocytes, macrophages, dendritic cells, astrocytes, mast cells, eosinophils, fibroblasts, epithelial cells, and endothelial cells. Galectin-9 binds to β-galactosides and can serve as a ligand for TIM-3 (CD366). The protein is implicated in both innate and adaptive immune responses specifically, induction of cytokine secretion by macrophages, bactericidal functions, promotion of dendritic cell maturation, regulatory T cell expansion, and negative regulation of Th1, Th17, NK, and cytotoxic T cells. The RG9-35 antibody has been reported to block some biological activities of Galectin-9 when administered in vivo.