Decreased Density in Membrane Localized Macromolecules in Cells Enlarged after X-Irradiation or Polyploidization

Cytophotometric measurements of DNA, dry mass (total proteins) and surface localized IgM and la were performed on individual cells of a Burkitt lymphoma derived cell line after Xirradiation and after polyploidization. Blockage of cell division was achieved with 250 r, and an arrest in G2 was found 48 hr after irradiation. The cells unable to divide increased in volume and total protein content. Cell enlargement was also achieved by polyploidization. The amount of surface localized IgM and la did not keep up pace with the increase in total proteins, thus their density decreased. This was reflected in decreased sensitivity of the enlarged cells to the cytotoxic effect of specific antisera.