MMP9 and arthritic joint disease: However, neither MMP‐9 (12.5 ± 3.1%, n = 12 vs. 5.3 ± 3.1%, n = 4), total leukocyte number (10424 ± 1328 cells/mm2, n = 8 vs. 11438 ± 608 cells/mm2, n = 21), nor neutrophil numbers as estimated by Ly6G signal (0.6 ± 0.2%, n = 10 vs. 1.9 ± 0.9%, n = 4) were significantly increased following arthritis onset (data not shown).