Independent cyclic fluctuations of cell surface parameters: expression of H-2 antigens, rosetting capacity and...

Cultures of a mouse X mouse cell hybrid (synchronized either by hydroxyurea or Colcemid) were tested for fluctuations during the cell cycle of several parameters characterizing the cell surface: expression of H-2 antigens, capacity of the cells to form rosettes with sheep red blood cells and thickness of the cell coat. H-2 antigenicity of cells collected at different phases of the mitotic cycle was assessed on the basis of their capacity to bind 125I-labelled antibodies as well as their sensitivity to complement dependent immune lysis. The latter parameters fluctuated more or less independently: around mitosis, their trends were even opposite and minimum antibody-binding capacity roughly coincided with maximum cytolytic sensitivity. The cyclic fluctuations of H-2 antigenicity were similar, but not identical for two antigens contributed to the cell hybrid by different parents and even the curves for two antigens of the same parental origin displayed a slight shift one from another. The frequency of cells forming large rosettes (i.e., of more than six SRBC) reached its peak roughly at the boundery of G1 and S phase. Mitotic (versus non-mitotic) cells had a significantly thicker cell coat (as visualized by ruthenium red staining and electron microscopy) and a high incidence of morphological abnormalities. The tested parameters thus seem to fluctuate independently of each other.