Immunologically induced acute synovitis in rabbits. Studies of immune complexes in synovial fluid

Large antigen-antibody complexes that are selectively removed from circulation were not selectively removed when injected into the knees of a normal rabbit. The subsequent selective removal of the complexes depended on the influx of neutrophils. Nevertheless, macrophages of the normal synovial lining were able to phagocytize some immune complexes. When antigen and antibodies were administered separately by intravenous or intraarticular routes, little or no soluble complexes were found in synovial fluid, and most of the antigen-antibody union was thought to occur in the synovial tissue.