Variations in antigen expression during the cell cycle of a human B-lymphoblastoid cell line

Expression of six surface markers during the cell cycle of a human B-lymphoblastoid cell line has been examined. Cultures were synchronised by a double thymidine block, then monitored through a complete cell cycle following release. Surface marker expression was studied by manual immunofluorescence and flow cytometry. Surface topography of the cells during the cycle was examined by scanning electron microscopy. Some variation in the expression of all markers was observed during the cell cycle. Four antigens (surface membrane immunoglobulin, common ALL antigen, an immature cell marker identified by monoclonal antibody 11D1, and an ubiquitous leucocyte antigen identified by monoclonal antibody 6B1) showed maximal expression in S and/or G2 phase and minimal expression during mitosis. These results could be due to changes in cell size. However, the individual patterns of expression of these four antigens during the phases of the cell cycle implied that changes in antigen density also occurred, at least in some cases. In contrast, expression of HLA-A, B, C and Ia antigens did not parallel cell size and was lowest during the S and G2 phases, increasing to a peak in early G1 phase.