MMP9 and rheumatoid arthritis: However, it was interesting to observe that the downregulation of KLF2 expression and concomitant upregulation of several inflammatory markers, including TNFα, MCP1, MMP1, MMP9, and MMP13, in primary monocytes isolated from the peripheral blood of patients with active RA (Figure 6C) established the inverse correlation between KLF2 levels and severe arthritic induction in humans.