Comet assay and early apoptosis.

The comet assay is a single cell gel electrophoresis test currently used as a qualitative and quantitative genotoxicity test. However, some of the results from this comet assay and current knowledge on apoptosis lead us to suspect the presence of some false positive results. The aim of this study was to ascertain if apoptotic cells can yield comet images that might distort the interpretation of the results. Using Jurkat cells, that hardly express Fas antigen, and apoptosis induction with anti-Fas antibody, it was possible to show that apoptosis can generate typical comet pictures as soon as the cells enter the apoptosis process. Therefore, comet images cannot be interpreted as a genotoxicity indicator when an apoptosis risk is present. Yopro-1 staining, that is also nearly immediate after apoptosis induction, can be used to balance comet assay results.