HAb18G/CD147 antagonistic peptide AP-9 (200 μg/ml) was found to have inhibitory effects on the MMP release and activation of co-cultured RA FLS and THP-1 cells (differentiated and undifferentiated), and on co-cultured RA FLS and monocytes/macrophages from healthy peripheral blood or rheumatic synovial fluid (P < 0.05; Figures 2a,d,e and 3a,c,d). Here, BSG is linked to rheumatoid arthritis.