Symmetrical synovial fluid cell cytokine messenger RNA expression in rheumatoid arthritis: analysis by reverse transcription/polymerase chain reaction

To investigate the complex intra-articular immune activity in rheumatoid arthritis (RA), we analysed the expression of a wide range of cytokine mRNAs in synovial fluid cells from patients with rheumatoid arthritis. To minimize in vitro artefact, mRNA was rapidly extracted from synovial fluid leucocytes taken from single joints of seven patients and simultaneously from both knee joints of four patients. Expression of interleukin (IL) 1 beta, IL-2, IL-4, IL-6, IL-8, IL-10, granulocyte-macrophage colony-stimulating factor, tumour necrosis factor-alpha and interferon-gamma (IFN-gamma) was detected using the reverse transcription/polymerase chain reaction. The expression of cytokines varied between patients. IFN-gamma mRNA was detected in 60% of the patients and IL-4 mRNA in 10%. Cytokine expression in both knees was very similar. These results suggest that T-cell activity in RA is detectable using sensitive techniques and that the intra-articular immunopathology of RA is systemically very similar.