A soluble form of the adhesion receptor CD58 (LFA‐3) is present in human body fluids

The human adhesion receptor CD58 (LFA‐3) is expressed on most human cell types. Here we report on a soluble form of CD58 (sCD58) in human serum, human urine, and culture supernatants of several cell lines. sCD58 partially purified from human serum, from supernatant of the Hodgkin cell line L428, and purified sCD58 from human urine were found to have a molecular mass of 40‐70 kDa under denaturating conditions (sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and Western blotting). However, gel filtration of sCD58 purified from human urine gave a molecular mass of 118‐166 kDa, suggesting a noncovalent homotrimer conformation or its association with other molecules. Using an enzyme‐linked immunosorbent assay specific for CD58 we found that sera from patients suffering from different forms of hepatitis contained elevated sCD58 levels (n = 108). Accordingly, there was a fivefold increase of supernatant sCD58 when the hepatocellular carcinoma cell line Hep G2 was incubated with 25 ng/ml recombinant tumor necrosis factor‐α in vitro. In contrast, sCD58 serum levels of 337 additional patients suffering from various other immunological disorders were not found to be raised. At high concentrations sCD58 binds to CD2‐positive cells and inhibits rosette formation of human T cells to human erythrocytes. Thus, local release of large quantities of naturally occurring sCD58 may interfere with intercellular adhesion in vivo.