Sialic acid, intercellular adhesion molecule-1 and rheumatoid arthritis: a study on the erythrocyte membrane.

We measured serum levels of soluble intercellular adhesion molecule-1 and erythrocyte membrane sialic acid in patients with rheumatoid arthritis and studied their correlation with the disease activity. Serum soluble intercellular adhesion molecule-1 level was determined with sandwich ELISA and sialic acid level with the method of Shamberger in 42 patients with rheumatoid arthritis and in 30 healthy controls. Significantly lower erythrocyte membrane sialic acid and higher serum levels of soluble intercellular adhesion molecule-1 were found in patients with rheumatoid arthritis compared with healthy controls (p<0.001 for both). Significant negative correlation between soluble intercellular adhesion molecule-1 level and erythrocyte membrane sialic acid concentration (r=-0.49, p<0.001) and positive correlations between soluble intercellular adhesion molecule-1 level and Ritche Articular Index score and C-reactive protein (r=0.32, p<0.05; r=0.44, p<0.01, respectively) were observed. From these data we conclude that decreases in erythrocyte membrane sialic acid concentration and increases in soluble intercellular adhesion molecule-1, erythrocyte sedimentation rate and C-reactive protein levels are present in rheumatoid arthritis, and that the increased soluble intercellular adhesion molecule-1 in rheumatoid arthritis might be due to the decreased erythrocyte membrane sialic acid concentration. The levels of soluble intercellular adhesion molecule-1 may be a novel marker for the disease status and the activity of rheumatoid arthritis.