Gamma delta and alpha beta T cells are equally susceptible to apoptosis

Little is known about the role of apoptosis in the regulation of gamma delta T cell development and function. We have used chicken as a model to study apoptosis of gamma delta T cells at different stages of their development. Apoptosis was measured with electrophoretic analysis of DNA fragmentation and flow cytometric determination of DNA content combined with immunofluorescence staining of cell surface molecules. In vitro culture, dexamethasone, and gamma-irradiation induced apoptosis of both gamma delta TCR+ thymocytes and peripheral gamma delta T cells. Apoptosis could be induced even in the earliest thymic gamma delta thymocytes on embryonic day 13. Resting peripheral blood gamma delta T cells were more resistant to apoptosis than thymocytes and spleen cells. Following polyclonal activation of splenic gamma delta T cells by Con A, the proportion of the CD8+ gamma delta T cell blasts decreased significantly when recultured without further stimulation. These results indicate that gamma delta T cells are susceptible to apoptosis in a manner similar to alpha beta T cells, and suggest that apoptosis plays an important role in the regulation of the development and function of both thymic and peripheral gamma delta T cells.