Background and aims Increased levels of MMP-9 were reported in serum samples of SLE patients versus healthy controls, with the suggestion that MMP-9 plays a negative role in SLE.^1-3 As a contrast, others demonstrated an inverse correlation between the levels of MMP-9 and anti-dsDNA in serum of SLE patients,⁴ the latter being a marker of disease severity.

The double knock-out mice model B6^lpr/lprMMP-9^-/- mice shows reduced survival with extreme lymphadenopathy and splenomegaly, high lymphoproliferation, increased autoantibody (aAb) production and pronounced autoimmune tissue injury comparing with B6^lpr/lpr.⁵ These data supports our suggestion that MMP-9 plays an important role in the clearance of autoantigens (aAg).⁵

Methods Our present goal is to analyse if MMP-9 plays a role in immune complex (IC) clearance.

Biochemical and molecular techniques

Results Our data suggested that MMP-9 degrades aAg, coupled to immunoglobulins in IC, but the efficiency of cleavage depends of the nature of the IC. Our preclinical data in the B6^lpr/lpr lupus animal model were validated with samples from SLE patients.

Conclusions All these data may be interpreted in the way that MMP-9 acts as a protective factor in the development of the disease. Consequently, a profound study of the role of MMP-9 in SLE will generate new and interesting data about pathophysiology and progression of the disease and allow us to develop new effective treatment options

References

1. Clin Biochem 2008;41:955–9.

2. Arthritis Res Ther 2004;6:R551–6.

3. Arthritis Rheum 2004;50:858–65.

4. Mol Pathol 2003;56:244–7.

5. J Autoimmun 2011;36 :239–52.