Induction of micronuclei and apoptosis in natural killer cells compared to T lymphocytes after gamma -irradiation

PURPOSE: To investigate the chromosomal damage caused by gamma-irradiation in T lymphocytes and natural killer (NK) cells and compare this with apoptosis induction in both lymphocyte subsets. MATERIALS AND METHODS: Apoptosis induction by gamma-irradiation in T lymphocytes and NK cells was quantified using the annexin V flow cytometric assay. The cytokinesis-block micronucleus (MN) assay was used to evaluate the induced cytogenetic damage. For the MN assays on NK cells, gamma-irradiated peripheral blood mononuclear cells were cultured and stimulated with interleukin 15 (IL-15). Afterwards the NK cells (characterized by the CD3-/CD56+ phenotype) were separated with the FACSort flow cytometer and the number of MN in the sorted binuclear cells was scored. Doses of 1 and 2 Gy gamma-irradiation were applied. RESULTS: Higher numbers of MN in NK cells were found compared with the MN yield in T lymphocytes. In contrast, NK cells were less than T lymphocytes prone to apoptosis after gamma-irradiation. CONCLUSION: The results support the view that cytogenetic damage and apoptosis after gamma-irradiation are not necessarily correlated.