T-helper (Th) cell-mediated immunity is required to eliminate pathogens effectively but unrestrained Th activity can contribute to tissue damage in many inflammatory and autoimmune diseases. The T-cell immunoglobulin and mucin domain-containing protein (HAVCR2, TIM3) inhibits T-helper type 1 lymphocyte (Th1)-mediated auto- and allo-immune responses and promotes immunological tolerance when it binds to its ligand, galectin-9 (LGALS9). The HAVCR2:LGALS9 complex achieves this inhibition by inducing apoptosis of Th1 cells. The human event is inferred from experimental data from mouse studies (Sanchez-Fueyo et al. 2003, Zhu et al. 2005).