ELEVATED INTERLEUKIN-10 LEVELS IN PATIENTS WITH RHEUMATOID-ARTHRITIS

Objective. Interleukin-10 (IL-10) has been shown to exert both antiinf lammatory and immunostimulatory effects in vivo and in vitro. We there fore sought to examine the role of this cytokine in rheumatoid arthrit is (RA) by assessing serum and synovial fluid IL-10 levels. Methods. S erum and synovial fluid samples were collected from patients with RA a nd patients with various inflammatory, infectious, and noninflammatory arthritides (controls). IL-10 was assayed using an IL-10-specific enz yme-linked immunosorbent assay, and messenger RNA (mRNA) levels were a ssessed by semiquantitative polymerase chain reaction (PCR) techniques . Results. Both RA serum and synovial fluid contained significantly el evated IL-10 levels compared with levels in normal subjects or in cont rol patients (P < 0.01). Some patients with spondylarthropathy also ma nifested increased serum levels of IL-10. Serum levels of IL-10 did no t correlate with standard measures of clinical activity, but were show n to correlate significantly with serum rheumatoid factor (RF) titers and in vitro levels of spontaneous IgM-RF production (P < 0.05). PCR a nalyses demonstrated the constitutive expression of IL-10 mRNA by the non-T cell population, and semiquantitative PCR analysis documented el evated levels of IL-10 mRNA in circulating mononuclear cells of those RA patients who were not treated with slow-acting antirheumatic drugs. Analysis of IL-10 mRNA revealed the cytokine to be of human, and not viral, origin. Conclusion. These data suggest that there is increased production of IL-10 by non-T cells in patients with RA. This may contr ibute to the diminished T cell function and increased antibody and RF production in these patients.