Self-associating IgG rheumatoid factors stimulate monocytes to release prostaglandins and mononuclear cell factor that stimulates collagenase and prostaglandin production by synovial cells.

Self-associating IgG rheumatoid factors isolated from three patients with rheumatoid arthritis activated human monocytes to release prostaglandin E2 as well as a previously described mononuclear cell factor, which stimulates human synovial cells to release additional prostaglandin E2 and collagenase. Thus, the immune complexes composed of self-associating IgG rheumatoid factors can contribute to the processes that destroy cartilage and bone in patients with rheumatoid arthritis.