PROS1 and rheumatoid arthritis: In addition, Sa ́nchez-Pernaute et al. [41] found that C4BPB was over-expressed in the synovial membranes of patients with rheumatoid arthritis and indicated that C4BPB was involved in the inactivation of the protein C anti-coagulatory pathway by coupling with protein S, thus contributing to the restoration of tissue integrity.