EARLY DETECTION OF APOPTOSIS IN DEFINED LYMPHOCYTE POPULATIONS IN-VIVO

Recently many methods have been developed for the detection of apoptos is. However, all of them have some limitations in determining whether specific subsets of cells are undergoing apoptosis. In this paper we d escribe a technique in which one simultaneously stains for cell surfac e markers with fluorescent monoclonal antibodies and for nuclear DNA b reaks using in situ DNA nick translation detectable by fluorescence. T he method has been evaluated using radiation-induced programmed cell d eath of lymphocytes and compared with some other techniques. It was fo und that the method is very specific and sensitive. It enabled us to e numerate apoptotic cells at the single cell level and simultaneously d etermine their subset-specific surface antigen profile both in vivo an d in vitro. It is also insensitive to nicks present in replicating cel ls. Our data suggest that this method may be useful for the study of p rogrammed cell death of antigen specific T cells in vivo.