TIMP1 and rheumatoid arthritis: Therefore, the aim of our present study was to evaluate the effects of the repeated infusions of rituximab, a monoclonal antibody against CD20+ B cells, on the serum MMP-1, MMP-3, MMP-9 and TIMP-1 levels, and ratios of measured MMPs to TIMP-1 in patients with active RA refractory to anti-TNF treatment.