LGALS9 and systemic lupus erythematosus: As a negative regulatory checkpoint shared by a variety of immune cells, T-cell immunoglobulin and mucin-domain containing-3 (TIM-3) and its ligand galectin-9 are best known for their high expressions in SLE patients [121,122,123] and have also been reported to be correlated with the activity of the disease [124,125].