Correlation of Serum Interleukin-8 and Cell Surface Lysosome-associated Membrane Protein Expression with Clinical Disease Activity in Systemic Lupus Erythematosus

Cell surface expression of lysosome-associated membrane proteins (LAMPs) correlates with serum interleukin-8 (IL-8) levels, shorter disease duration, greater functional impairment from disease-related symptoms and soluble IL-2 receptor levels (sIL-2R) in patients with scleroderma. In this study of 46 patients with systemic lupus erythematosus (SLE), the relationship of serum IL-8 and cell surface LAMP to two clinical measures of disease activity, the SLEDAI and SLAM scales, was evaluated. IL-8 levels were determined on serum samples by the immunometric sandwich enzyme immunoassay technique. Cell surface LAMP expression was determined by flow cytometric quantitation of peripheral blood mononuclear cells with monoclonal antibodies directed against two of the major LAMP proteins, lamp1 and lamp2. The clinical disease activity scales correlated significantly with each other, with C3 levels, serum IL-8, C4, dsDNA and sIL-2R. Lamp1 and lamp2 expression correlated with the SLAM but not the SLEDAI scale. Serum IL-8 levels were elevated in 49 of 51 samples tested (44 of 46 patients) and had a stronger correlation with disease activity than C4, dsDNA and sIL-2R levels. Significantly higher levels of IL-8 were seen in patients with evidence of renal involvement. Serum IL-8 and cell surface LAMP expression may be useful indicators of disease activity in patients with SLE. The possible role of IL-8 in the pathogenesis of SLE requires further investigation.