Tissue-infiltrating primary monocytes are proteolytically competent (Van Goethem et al, 2009), and serve as a major source of MMP2 and MMP9 in the RA joint (Zhou et al, 2014), implicating these cells as potential mediators of collagen VI turnover in the perivascular space. The gene discussed is MMP9; the disease is rheumatoid arthritis.