HOXD13 and systemic sclerosis: We hypothesized that soluble immune checkpoints (sICPs) reflect immune activation and serve as biomarkers for disease activity and treatment response.<h4>Methods</h4>Plasma levels of 15 sICPs (including sPD-1, sTIM-3, sBTLA, sCD25, sCD137, sIDO), cytokines, B cell activating factor (BAFF) and dephosphorylated-uncarboxylated Matrix Gla Protein (dp-ucMGP) were analyzed in a prospective SSc cohort (n = 35).