Restricted cytokine expression in rheumatoid arthritis

Abstract

Objective. To determine the cytokine profile of the phenotypically activated T cell in rheumatoid arthritis (RA) synovium. Methods. Interleukin‐2 (IL‐2), IL‐2 receptor (IL‐2R), IL‐6, IL‐4, and interferon‐γ (IFNγ) gene expression was examined in T cells from freshly isolated synovial fluids (SF) and synovial tissues (ST) from patients with RA. Estimates of baseline expression were determined using unstimulated peripheral blood (PB) T cells from healthy individuals. The corresponding positive controls were phytohemagglutinin‐activated tonsil T cells. Results. In studies of paired PB and SF T cell samples from 17 RA patients, IL‐2 messenger RNA (mRNA) levels in only 1 PB and 3 SF samples were more than 2 standard deviations above the mean of levels in unstimulated PB from healthy donors. Similarly, only 5 PB and 7 SF samples exhibited elevated IL‐2R mRNA levels. IFNγ gene expression was not detected in any of the paired RA PB or SF samples. Fractionated T cells from 12 RA ST were screened with similar results: Only 1 of 12 samples exhibited IL‐2 mRNA levels more than 2 standard deviations above levels in baseline controls. IL‐2R mRNA levels were low or not detected, and IFNγ mRNA was absent. Subsequent studies showed that IL‐4 and IL‐6 gene expression levels were also low in RA tissues compared with tonsil T cell–positive controls. Conclusion. These data provide evidence for restricted cytokine expression in the T cell population in RA tissues.