Human bymphoblasts of the CCRF-CEM cell line initially isolated from the peripheral blood of a pediatric beukemic

cently established and well characterized both morphobogi cabbyand biochemically (11). Due to their unique growth ct@'@cteristics and increased sensitivity to a variety of chem icab .gents (6), some of the techniques normally used for synchronization of nonlymphoid cells are not directly appli cable to these cell lines. The recent availability of flow microfluorometry for rapid determination of DNA per cell (21) has made it relatively easy to follow the progression of a synchronized population through the cell cycle (20). We have used this technique in combination with [3H]TdR incorporation to follow the cell cycle traverse of human lymphoid cells synchronized by a variety of methods.4 In the present report we describe synchronization of human lymphoblasts of the CCRF-CEM cell line by exposure to the DNA synthesis-inhibitory drug IMPY (1, 5).