Response of the rheumatoid synovial membrane to exogenous immunization

The secondary immune response to tetanus toxoid in 14 patients with rheumatoid arthritis (RA) has been studied in suspension cultures of peripheral blood lymphocytes (PBL) and synovial membrane obtained at synovectomy. Sequential cultures of PBL from three normal subjects established the optimal time of antibody response at 5 days. At this time, the antitetanus antibody produced was predominantly IgG, comprising half of this immunoglobulin fraction. Rheumatoid synovium synthesized 5-9 times more IgG than PBL, expressed as per cent of total protein synthesis, but only negligible amounts of tetanus antibody. The same results were observed in synovial cultures following repeated immunization and after the additional intra-articular injection of tetanus antigen. This marked limitation of the synovium to respond to exogenous antigen in spite of its large immunoglobulin production was considered consistent with a prior commitment of the synovial lymphoid infiltrate to other antigen.