Abstract
Monoclonal antibodies specific to HLA antigens and the fluorescence-activated cell sorter were used to analyze the changes in the density of human histocompatibility antigens HLA-A,B and HLA-DR on the surface of synchronously growing WI-L2 cells (a human B cell line) progressing through the cell cycle. The WI-L2 cells were synchronized by density-dependent arrest in G1, and samples from G0, G1, late S and late G2 phases were used to determine the frequency distribution of cell volume, DNA content, and the relative amounts of cell surface HLA antigens; the observed density changes were calculated from these values. The HLA-A,B density remained nearly constant throughout the cell cycle, whereas the HLA-DR density increased sharply at the G2-M stage. These results suggest a cell cycle-dependent differential control of the expression of these two sets of histocompatibility antigens on B cells.