Expression of H-2 Antigens Durin Growth of Cultured Tumor Cells

H-2 antigens cell surface expression has been investigated in murine cultured tumor cells L1210 at different stages of their growth. H-2 antigens are maximally expressed during the mid-log phase of cell growth as judged by the sensitivity of cells to antibody mediated lysis in the complement dependent cytotoxic test and by the absorbing capacity for H-2 antisera. The yields of H-2 antigens solubilized from cells at different stages of growth correlated consistently with the cell surface expression of these antigens.Mouse histocompatibility (H-2) antigens are genetically determined cell surface markers which are expressed on most murine cells and tissues. Since Medawar's (1) discovery that allograft survival could be prolonged by non-particulate murine transplantation antigens, it has been attempted to solubilize these antigens from the surface of cell membranes. A variety of methods have been applied and considerable efforts were made to characterize the biological as well as chemical natures of both human and murine histocompatibility antigens (2,3,4). Cultured lymphoid cells have been extensively utilized for the solubilization of these antigens, since such cells provide a genetically uniform source and are readily available in large amounts (5,6,7).While determining optimal extraction conditions for H-2 antigens from cultured murine tumor cells L1210, we observed great variability in yields of antigen obtainable from batches of cells harvested during different stages of the cell population curve. We had previously found the greatest yields of soluble HL-A antigens in the log growth phase of cultured human lymphoid cells derived from donors free of malignancy (8). Moreover, antigenic expression on these cells was essentially unchanged throughout the cell growth (9) in contradistinction to the reported finding of variable expression of H-2 antigens during the growth of murine tumor cells induced by viruses (10,11,12). These observations prompted us to determine whether yields of soluble H-2 antigens obtained during different growth phases correlate with the degree of expression of these antigenic determinants on the surface of cultured murine tumor cells.