Detection and characterization of HLA class I molecules in the supernatantof an hepatocarcinoma cell line and of EBV-transformed B cell lines

Human leukocyte antigens (HLA) class I molecules can be detect ed in "solub le" form in the supernatant of cultured cell lines and in serum and plasma of humans. These "soluble" HLA class I molecules are assumed to play a role in liver transplantation. In order to define the nature and composition of HLA class I molecules found in solution, we studied the HLA class I produc tion of an hepatoma carcinoma cell line (HepG2) and of EBV-transformed B-ce ll lines. Based on molecular weight (MW) analysis, it was demonstrated that different forms of HLA class I molecules were produced by HepG2 cells and EBV B-cells. Monoclonal antibodies (mAbs) specific for HLA class I alleles were able to recognize the mature 45 kDa form, but failed to interact with the 42 kDa and 39 kDa MW forms of HLA class I. Of these different MW forms of HLA class I molecules the mature 45 kDa product was found predominantly to be associated with subcellular vesicles whereas the alternative MW forms of 45 kDa and 33 kDa exist as truly free entities in supernatants. (C) Ame rican Society for Histocompatibility and Immunogenetics, 1999. Published by Elsevier Science Inc.