Interleukin 15 (IL-15) is a novel cytokine with interleukin-2-like activity. It is also a potent T-lymphocyte chemoattractant. Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by the presence of activated T lymphocytes, macrophages and synoviocytes in the synovial membrane. The mechanisms of T-cell activation in RA are currently unclear. We report the presence of high concentrations of IL-15 in rheumatoid arthritis (RA) synovial fluid and have demonstrated its expression in the synovial membrane lining layer by immunohistochemistry. RA synovial fluids were found to contain chemotactic activity, which was attributable in part to the presence of IL-15. Moreover, in a murine model, injection of recombinant IL-15 was found to induce a local tissue inflammatory infiltrate consisting predominantly of T lymphocytes. Synovial fluid T lymphocytes proliferate in response to IL-15, demonstrating that continued responsiveness to IL-15 is a feature of T cells after entry into the synovial compartment. These data suggest that IL-15 can recruit and activate T lymphocytes in the synovial membrane, thereby contributing to RA pathogenesis.

Diabetes mellitus and thyroid disease are common endocrine disorders in the general population. To investigate the association between thyroid dysfunction, thyroid autoimmunity and Saudi type 2 diabetics, a random sample of 100 Saudi type 2 diabetics and 100 age- and sex-matched controls were studied. The mean age was 54 years for diabetics and 55 years for controls while the male:female ratios were 1:1.6 and 1:14 respectively. GAD65ab were found in 26% diabetics and 2% controls (p=0.001). Thyroid autoimmunity were detected in 10% diabetics vs. 5% controls (p=0.05), while thyroid dysfunction was found in 16% and 7% respectively (p=0.03). In GAD65ab-positive diabetics, thyroid autoimmunity was observed in 27% vs. 4% GAD65ab-negative diabetics (p=0.02) and thyroid dysfunction was reported in 42% and 7% respectively. We conclude that thyroid dysfunction and autoimmunity are common in Saudi type 2 diabetics. Further studies are needed on the cost effectiveness of thyroid screening in diabetics.

SUMMARYThe majority of synovial fluids from 29 rheumatoid arthritis patients were strongly attractive for normal blood lymphocytes judged by assays of polarization and collagen gel invasion. While rheumatoid synovial fluids contained IL-15, IL-8, monocyte chemotactic protein-1 (MCP-1) and macrophage inflammatory protein-1® (MIP-1®) at levels sufficient to attract lymphocytes, inhibition of the activity of any single cytokine using specific antibody did not abolish the activity of the fluid. However combinations of anti-cytokine antibodies used together (anti-IL-15anti-MCP-1; anti-IL-8anti-MCP-1 or anti-MIP-1®) inhibited most of the activity, suggesting that attraction of lymphocytes by the fluids is due to a combination of attractants. Blood lymphocytes required activation by overnight culture to respond optimally, while rheumatoid synovial tissue lymphocytes responded to synovial fluids without a requirement for a period of culture. Lymphocytes derived from rheumatoid synovial fluids were poorly responsive to locomotor stimulants. Most of the responding cells from blood mononuclear cell fractions were T lymphocytes of the CD45RO isotype. Incubation in the presence of cyclosporin A or corticosteroids inhibited the response of lymphocytes to the fluids, but the presence of non-steroidal anti-inflammatory drugs (NSAIDs) and other agents used in therapy of the patients from whom the fluids were taken had no inhibitory effect.