DNA POLYMERASE ACTIVITY OF CULTURED NORMAL AND LEUKEMIC LYMPHOCYTES - RESPONSE TO PHYTOHEMAGGLUTININ

Normal lymphocytes when cultured with PHA showed increased DNA polymerase activity in 24 h. This preceded the onset of DNA synthesis. Further large increases in enzyme activity occurred in the next day or two of culture accompanying blast-cell formation and the start of mitosis. Leukemic lymphocytes from cases with low peripheral WBC counts showed the greatest increases in DNA polymerase activity and produced the largest numbers of blast-cells, while cells from cases with high WBC counts produced few or no blast-cells and failed to increase their DNA polymerase content. A broad spectrum of intermediate results were obtained in a series of 21 cases ranging in cell count from 21,000 to 265,000 per mm3. Initial studies indicate that a fluorimetric assay of cellular DNA may be a more satisfactory basis than initial cell count or protein determination for calculation of results of enzyme content of cells clumped by PHA. Increased DNA polymerase activity may be an essential preliminary to increased DNA synthesis in cells responding to PHA stimulation in cultures. © 1969.