Dimorphism of sister chromatid exchange in Bloom's syndrome B- and T-cell lines transformed with Epstein-Barr and adult T-cell leukemia viruses.

The present study describes the establishment of both B- and T-cell lines from the peripheral blood cells of two Bloom's syndrome (BS) patients and one healthy female by using Epstein-Barr (EBV) and adult T-cell leukemia viruses (ATLV). The cell lines from normal and BS subjects exhibited cell surface markers compatible with B- and T-cell origin; in addition, the BS B- and T-cell lines retained the original cytogenetic characteristics of the syndrome. Even though phytohemagglutinin-stimulated BS lymphocytes from the two BS patients studied all showed high levels of sister chromatid exchange (SCE), the established BS B-lines with EBV yielded two separate lines each, i.e., one with increased SCE and another with normal levels of SCE; also, one of the BS T-lines retained high SCE levels in 100% of the cells, whereas the other BS T-line contained two populations, one with high SCE (70%) and the other with normal SCE levels (30%), at a relatively constant frequency over a period of 6 months. Neither EBV nor ATLV caused a significant increase in chromosome instability in the established lines compared to fresh lymphocytes. Reinfection of the BS B- and T-cell lines with EBV or ATLV did not alter the SCE or karyotypes. These results strongly suggest that BS patients have two populations in vivo, one with high and another with normal levels of SCE, at least in the lymphoid cell system.