Differential regulation of rheumatoid synovial cell interleukin-12 production by tumor necrosis factor alpha and CD40 signals

Objective. To investigate the roles of tumor necrosis factor alpha (TNF alp ha) and the CD40-CD154 interaction in interleukin-12 (IL-12) production by rheumatoid synovial cells (SC), Methods. Levels of IL-12 (p40 and p70) in synovial tissue and culture super natants of SC from patients with rheumatoid arthritis (RA), osteoarthritis (OA), and ankylosing spondylitis (AS) were assayed by enzyme-linked immunos orbent assay. Effects of anti-CD154 and anti-TNF alpha antibody on spontane ous and lipopolysaccharide (LPS)-stimulated IL-12 production by SC were exa mined. Effects of immobilized anti-CD3 treatment and depletion of CD4+ T ce lls on IL-12 production were also tested. CD154 expression by synovial T ce lls and intracellular IL-12 production during culture were analyzed by flow cytometry, Results. IL-12 p40 and p70 levels in RA synovial tissue and spontaneous IL- 12 p40 production by SC from RA patients were significantly higher than the levels in OA and AS patients. Spontaneous IL-12 production by SC from RA, patients significantly decreased after depletion of CD4+ T cells from SC or after application of anti-CD154 antibody, but not by treatment with anti-T NF alpha antibody. Anti-CD3 antibody stimulation increased spontaneous IL-1 2 p40 production and CD154 expression by synovial T cells. The increment of IL-12 p40 production by anti-CD3 was abrogated by anti-CD154 antibody. IL- 12 p40 production was also increased by LPS stimulation. LPS-stimulated IL- 12 production was inhibited by anti-TNFa antibody, but not by T cell deplet ion and anti-CD154 antibody treatment. The TNF alpha inhibitor rolipram inh ibited LPS-stimulated IL-12 p40 production by RA SC more strongly than spon taneous production. TNF alpha restored LPS-stimulated IL-12 production that had been inhibited by rolipram. Conclusion. IL-12 production in RA is regulated by 2 different pathways. On e pathway is T cell dependent, predominantly through a CD40-CD154 interacti on, while the other is T cell independent, mediated through TNFa, Inhibitio n of IL-12 production by interference with CD40-CD154 interaction and TNF a lpha production may be a potential therapeutic strategy for treating RA.