Quantitative and biochemical characterization of soluble HLA class I antigens shed by cultured human cells.

sHLA has been described in human serum and other body fluids. In this study sHLA shed by cultivated human cells and their biochemical nature in solution were studied. EBV-transformed human B-lymphoblastoid cell lines (n = 4), permanent human lymphoblastoid tumor cell lines (n = 4), and PBLs from three donors were cultivated in vitro and sHLA measured in the supernatants. The Daudi cell line was used as a negative control in all experiments. Maximum expression of sHLA was measured after 8 hours, after which the concentrations gradually declined. The allospecificities A2 and B7 were also detectable in the ELISA. sHLA in the supernatants was further characterized by 1D-IEF. All bands representing the allotypes were detected, showing that cell supernatants can be used as antigen sources for biochemical tissue typing. These data show that sHLA expression is a characteristic of viable cells.