PROS1 and systemic lupus erythematosus: We also observed reduced proteolytic processing of inter-alpha-trypsin inhibitor heavy chain H1 (ITIH1) at A126 (log2FC SLE/CTRL −1.19), a protease inhibitor, and of PROS1 at F92 (log2FC SLE/CTRL −1.66), an anticoagulant protein with immunosuppressive abilities (Ubil et al, 2018).