Soluble intercellular adhesion molecule-1 in arthritis.

The objective of this study is to determine whether soluble intercellular adhesion molecule-1 (sICAM-1) is found in rheumatoid arthritis (RA) and other inflammatory disorders and to identify which cells are responsible for sICAM-1 production. Synovial fluid, blood and cells isolated from RA synovial fluids, and synovial tissues from 59 patients were studied. In addition, normal peripheral blood was obtained. sICAM-1 was assayed by an enzyme-linked immunoabsorbent assay. Synovial fluids from patients with RA and other inflammatory arthritides had significantly higher sICAM-1 levels than did osteoarthritis (OA) synovial fluids. Synovial fluid sICAM-1 levels were significantly positively correlated with synovial fluid leukocyte counts. RA synovial tissue fibroblasts released low levels of sICAM-1. Neutrophils (PMNs) isolated from synovial fluids of RA patients spontaneously released sICAM-1. However, mononuclear cells isolated from RA synovial fluid produced the largest quantities of sICAM-1. Phytohemagglutinin but not lipopolysaccharide enhanced mononuclear sICAM-1 release. sICAM-1 was increased in synovial fluids from RA compared to OA. This sICAM-1 may be important in modulating the trafficking of inflammatory leukocytes into diseased RA synovial tissue and fluid.