Expression of allograft inflammatory factor-1 in peripheral blood monocytes and synovial membranes in patients with rheumatoid arthritis.

OBJECTIVE:Allograft inflammatory factor-1 (AIF-1) is a cytoplasmic protein expressed in various human cells such as monocyte/macrophages and activated T lymphocytes. A recent study showed that AIF-1 is strongly expressed in infiltrating mononuclear cells and synovial fibroblasts in rheumatoid arthritis and that AIF-1 induces the proliferation of cultured synovial cells. In this study we analysed the expression of AIF-1 in peripheral blood monocytes and synovial membranes from patients with rheumatoid arthritis (RA). METHODS:We examined 71 patients with rheumatoid arthritis and 25 control subjects. RESULTS:Using flow cytometry we found significantly increased numbers of circulating AIF-1(+) monocytes in peripheral blood from RA patients compared with controls. Moreover, there were statistically significant positive correlations between AIF-1(+) monocytes, DAS28 and the Sharp erosion score. Immunofluorescence staining showed strong expression of AIF-1 by infiltrating mononuclear cells - predominantly macrophages in RA synovial tissues - compared with tissues derived from joints affected by osteoarthritis. CONCLUSION:The results of this study suggest that AIF-1 may be associated with the pathogenesis of RA and may be a novel cytokine involved in the immunological process underlying RA.

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