Immunopathogenesis of rheumatoid arthritis.

Three distinct groups of phenomena occur in the rheumatoid joint. The synovial lining cells proliferate and hypertrophy; the sublining or deep layer becomes infiltrated by mononuclear cells; and fluid, which is rich in polymorphonuclear cells, collects in the synovial space. As a result, there is a polymorphonuclear inflammatory reaction in the rheumatoid effusion and a chronic inflammatory reaction in the sublining layer of synovial membrane. In spite of their divergent histologic character, these two inflammatory reactions appear to be interrelated immunologically. In this review, we describe these two types of inflammation, trace their interrelationship and consider possibly underlying mechanisms for the inflammation.