Proliferation of human lymphocytes in culture : determination by measurement of nuclear volume and cell number.

Proliferation of stimulated human lymphocytes was studied in cultures by determining cell counts and nuclear volume enlargement. DNA content and the nuclear volume increase before the cell divides. Volume-frequency curves were obtained of unstimulated and phytohemagglutinin (PHA) stimulated lymphocytes on 0, 3, 6 and 9 days of cultures with the Coulter Counter H4 system. As the number of lymphocytes in the cultures transformed and enlarged in volume, the area under the volume-frequency curve increased proportionately. The fraction of transforming cells was determined by comparing the area under the curve of the unstimulated and the stimulated lymphocytes. This method provides both the fraction of cells transformed and the increment of the number of cells in the culture and is therefore a better indicator of cell proliferation than the commonly used isotope-labeled thymidine uptake method which monitors the fraction of the cells in DNA synthesis phase only.