Identification of a transitional preapoptotic population of thymocytes

摘要: Apoptosis, a major form of cell death in the immune system, is characterized by shrinkage, chromatin condensation, and cleavage into nucleosomal fragments. Apoptosis may be mechanism for elimination autoreactive unselected CD4+ CD8+ thymocytes thymus. A large number diverse agents are capable inducing apoptosis immature thymocytes. Rat were treated with etoposide, DNA topoisomerase II reactive agent, or dexamethasone, glucocorticoid, separated on discontinuous Percoll gradients. We have identified isolated transitional preapoptotic population that exhibited early morphologic biochemical changes associated apoptosis. These cells intermediate size density between normal apoptotic decreased surface expression both CD4 CD8 molecules compared to control On ultrastructural examination, they shown possess sharply defined clumps condensed abutting onto nuclear membrane. changes, first detectable signs apoptosis, occurred prior internucleosomal DNA, often regarded as hallmark Nucleosomal fragments 180 200 base pairs multiples thereof were, however, detected following subsequent dramatic structure these resulted morphology typical results suggest critical events precede DNA.