Frequencies of sister-chromatid exchanges in relation to cell kinetics in lymphocyte cultures

The frequency of sister-chromatid exchanges (SCE) was determined on second-division metaphases of lymphocytes stimulated by phytohaemagglutinin (PHA) during 9 days of culture. By using either a continuous or a pulsed bromodeoxyuridine (BUdR) treatment, cells were selected that had divided only twice, or at least twice, after different culture periods. No significant differences were observed in the SCE frequencies among the various samples. The incidence of SCE appears to be independent of the proliferation properties of cultured lymphocytes, such as length of cell cycle, fast or delayed response to PHA and number of divisions performed in vitro.