ENHANCED COSTIMULATORY ABILITY OF SYNOVIAL-FLUID ACCESSORY CELLS IN RHEUMATOID-ARTHRITIS

We have established in vitro assays that allow the examination of co-s timulatory function of rheumatoid arthritis (RA) antigen-presenting ce lls (APC). Synovial fluid (SF) and peripheral blood (PB) APC co-stimul atory ability was compared in the activation of peptide-specific human T-cell clones. T-cell receptor (TCR) stimulation by peptide or anti-C D3 antibody allowed the direct comparison of SF and PB APC co-stimulat ory activity, separately from their ability to process antigen. SF APC from 15 RA patients consistently enhanced T-cell proliferation when c ompared to their PB counterparts. Moreover, increasing the numbers of PB APC present resulted in only a minor increase in T-cell proliferati on, failing to achieve levels stimulated by SF APC. We propose that th e enhanced co-stimulatory function of synovial APC may be a significan t factor in the persistence of local immune responses in RA.