TIMP1 and rheumatoid arthritis: In our article, we evaluated the regulatory effects of the infusions of rituximab, a monoclonal antibody directed against CD20+ B cells, on the serum matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases-1 (TIMP-1) levels in patients with active rheumatoid arthritis (RA) not responding to anti-tumor necrosis factor (anti-TNF) therapy.