Factors influencing sister-chromatid exchange rate in cultured human lymphocytes

Factors influencing sister-chromatid exchange (SCE) frequency in human lymphocytes were investigated. Slides treated by the hot PO4 technique showed a lower SCE rate than those treated by the fluorescence plus Giemsa (FPG) technique. Lymphocytes cultured in McCoy's 5A culture medium showed a lower SCE rate than those cultured in TC 199. Neither of the 2 batches of serum tested (Gibco batch 092 and human AB) increased the SCE rate. Cultures harvested at 48 and 72 h showed similar SCE rates. The mean SCE rate in lymphocytes from 100 subjects was 10.98 with a standard deviation of 1.71. Only 3 donors fell outside the 95% confidence level. The distribution of SCE in individual cells was judged to differ significantly from normal. Cells with increased SCE contributed to the positive skewness of the distribution. Repeat cultures from 20 subjects were studied over a 3-year period. Only 3 subjects showed significant variation in SCE in successive cultures.