UV-C sensitivity of unstimulated and stimulated human lymphocytes from normal and xeroderma pigmentosum donors in the comet assay: a potential diagnostic technique.

We have studied incision-break formation in unstimulated and stimulated populations of human T-lymphocytes using the comet (single-cell microgel electrophoresis) assay. The frequency of strand breaks 1 h after UV-irradiation appears to be far greater in unstimulated than in stimulated lymphocytes from normal donors and the excess of strand breaks was observed for a far longer time after irradiation. This result corroborates the greater sensitivity of UV-C irradiation observed in a colony-forming assay but suggests that the defect may relate to a defect in strand rejoining rather than a defect in incision. Few strand breaks were seen in either unstimulated or stimulated lymphocytes of four xeroderma pigmentosum donors, suggesting that the method may offer a rapid diagnostic assay for XP.