RA (Rheumatoid Arthritis) is a chronic debilitating autoimmune disease of unknown etiology affecting diarthrodial joints. The pathology of RA is characterized by the infiltration of several inflammatory cells into both the pannus and the joint fluid, and ...by subsequent tissue destruction. Although the disease is characterized by synovitis of the joints, tendon sheaths, and bursae, manifestations that do not involve the synovium are also frequent. These articular and systemic manifestations are mediated by hyperplasia of the synovial lining cells and extensive infiltration of macrophages, lymphocytes, fibroblasts, and leukocytes in joints, where a variety of cytokines, prostaglandins and proteolytic enzymes, are responsible for the process of the inflammation. The hallmarks of the synovial abnormalities in RA are synovial lining cell proliferation, neoangiogenesis, and inflammatory cell infiltration involving the myeloid, macrophage, and lymphoid lineages. In addition, the fluid-filled joint cavity contains numerous neutrophils, particularly during acute flares of RA.
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