Induction and disappearance of DNA single-strand breaks in human B and T lymphocytes after exposure to ethylnitrosourea

Using the alkaline filter elution technique we monitored the induction and disappearance of DNA single-strand breaks (SSB) in 3 different human lymphocyte populations: (1) freshly isolated peripheral blood lymphocytes (PBL); (2) B and T cell-enriched lymphocyte fractions; and (3) actively proliferating T cells, after exposure to ethylnitrosourea (ENU). Between these different lymphocyte populations no significant differences were observed in the number of SSB induced by a 20-min treatment with 0.5 mM ENU. SSB disappearance was observed in PBL of some but not all individuals, confirming our earlier results (Boerrigter et al., 1990a). Determinations on B and T cell-enriched lymphocyte populations indicated that ENU-induced SSB were removed only in T lymphocytes; no significant amount of SSB disappearance was observed in B lymphocytes. In contrast, no differences in SSB repair between B and T lymphocytes were found after gamma-irradiation. Induction and disappearance of ENU-induced SSB were found not to be dependent on the proliferative status of T lymphocytes; no differences were observed between quiescent PBL or T lymphocytes and actively proliferating T cells from the same donor, with respect to either the rate or the total amount of ENU-induced SSB disappearance.