Therefore, we hypothesized that other soluble forms of coinhibitory receptors and their ligands, such as galectin-9 (the ligand of TIM-3) and CD155 (the ligand of T cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain), may also play a role in the pathogenesis of SSc. Here, LGALS9 is linked to systemic sclerosis.