Interleukin-2 is found in the synovium of psoriatic arthritis and spondyloarthritis, not in rheumatoid arthritis

The involvement of NK cells in ankylosing spondylitis

A role for NK cells in the regulation of autoimmunity has been demonstrated. Since there is a strong association between Ankylosing Spondylitis (AS) and HLA-B27, which is specifically recognized by the NK-inhibitory receptor KIR3DL1, this study evaluated the potential involvement of NK cells in AS. We studied 19 AS patients and 22 healthy volunteer donors and assessed the percentage, activity and receptor expression of peripheral blood NK cells. We also evaluated candidate-inflammatory mediators in sera. We found that AS patients have significantly higher percentages of NK cells. However, we found no differences between the ability of NK cells derived from AS and healthy controls to recognize target cells expressing HLA-B27. Remarkably, we observed that the NK-inhibitory receptor CEACAM1 (carcino-embryonic antigen-cell adhesion molecule) is highly expressed among AS-derived NK cells. Furthermore, engagement of CEACAM1 inhibited NK activity in these patients. Finally, we demonstrated that CEACAM1 expression is induced by IL-8 and SDF-1 (stromal cell derived factor), both of which are present in high levels in the sera of AS patients. These results may indicate that NK cells and CEACAM1 play a role in AS pathogenesis and implicate chemokines in the mechanism of CEACAM1 expression.

Reduction of synovial sublining layer inflammation and proinflammatory cytokine expression in psoriatic arthritis treated with methotrexate

OBJECTIVE

Methotrexate is one of the most commonly used disease-modifying antirheumatic drugs in the management of psoriatic arthritis (PsA). Despite the differences between the inflammation in PsA and rheumatoid arthritis (RA), the effects of methotrexate on the synovium have been described solely in RA. In this study, we sought to determine the effects of methotrexate on the inflammatory infiltrate and on cytokine and metalloproteinase gene expression in the synovium of PsA patients.

METHODS

Ten patients with PsA (median duration 18 months) underwent arthroscopy and synovial biopsy of an inflamed knee before and after clinical improvement induced by methotrexate. Immunohistologic analysis was performed using antibodies to CD3, CD4, CD8, CD68, factor VIII, vascular cell adhesion molecule, E-selectin, and intercellular adhesion molecule (ICAM). Matrix metalloproteinase 3 (MMP-3) and tissue inhibitor of metalloproteinases 1 (TIMP-1) messenger RNA (mRNA) were quantified by competitive reverse transcription-polymerase chain reaction (RT-PCR). Interleukin-1alpha (IL-1alpha), IL-1beta, IL-2, IL-4, IL-5, IL-8, IL-10, IL-12p35, IL-12p40, IL-15, interferon-gamma (IFNgamma), and tumor necrosis factor alpha (TNFalpha) mRNA expression was quantified by real-time PCR.

RESULTS

Patients received a median methotrexate dosage of 13.75 mg/week (range 7.5-15) for a median of 11.5 months (range 7-14 months). The Ritchie Articular Index, swollen joint count, and Disease Activity Score were significantly reduced. There was a decrease in all immunohistologic staining, although this was statistically significant only for CD3, CD4, CD8, CD68, E-selectin, and ICAM. Despite clinical improvement in all patients, there was a residual T cell infiltrate in all synovial biopsy tissues. The synovial lining layer thickness, but not hypervascularity, was significantly reduced. There was also a significant reduction in MMP-3, but not TIMP-1, expression. Before treatment, PsA synovium was characterized by a predominant expression of the proinflammatory cytokines IL-15, IFNgamma, IL-1beta, and TNFalpha and the antiinflammatory cytokine IL-10. Methotrexate reduced synovial IL-1alpha, IL-1beta, IL-8, IL-10, IL-15, IFNgamma, and TNFalpha mRNA expression, but the effect was significant only for IL-8.

CONCLUSION

Methotrexate produced a clinical response in PsA by reducing, but not abolishing, the inflammatory infiltrate, adhesion molecule expression, and MMP-3 and proinflammatory cytokine gene expression, particularly IL-8, in the synovium. Methotrexate did not reduce hypervascularity, which is a prominent differentiating feature of PsA synovium.

Genetic epidemiology. Psoriatic arthritis

The existence of psoriatic arthritis as a distinct clinical entity remains a topic of debate; some authors propose that it is simply the co-occurrence of psoriasis and inflammatory arthritis. However, a distinct entity is likely to have distinct susceptibility factors in addition to those that contribute to psoriasis and inflammatory arthritis alone. These aetiological factors may be genetic and/or environmental, and in this review, the evidence for distinct psoriatic arthritis genetic susceptibility factors is considered.

Pathways of cell activation in spondyloarthropathies

The initiating event in cell activation is unknown in most autoimmune diseases. The role of infection is clear in some cases, especially in reactive arthritis; however, there is little evidence of a specific organism in other spondyloarthropathies. Common pathways of cell-cell interaction and activation manifest in inflammation, but subtle differences may exist. The presence of T cells, macrophages, and B-lymphocytes suggest an autoimmune mechanism; the arthritogenic peptide theory has been proposed. Furthermore, the association of spondyloarthropathies with HLA-B27 suggests it may be important in synovial T-cell activation. Other cell types involved in the process of bone and cartilage destruction, including fibroblasts and osteoclasts, may also be activated. Endothelial activation and angiogenesis may be a critical primary event in these diseases. Finally, trauma (physical or psychological) in the form of stress may be an important factor; the nervous system and neuropeptides may play a role in cell activation and initiation of arthritis.