The Journal of Immunology, Vol 154, Issue 9 4371-4378, Copyright © 1995 by American Association of Immunologists

ARTICLES

In situ detection and characterization of apoptotic thymocytes in human thymus. Expression of bcl-2 in vivo does not prevent apoptosis

PT Le, HT Maecker and JE Cook
Department of Cell Biology, Loyola University Medical Center, Maywood, IL 60153, USA.

Apoptosis plays a crucial role in shaping the T cell repertoire during T cell development in the thymus. The observed disappearance in the thymus of CD4+ CD8+ thymocytes with a specific TCR, and the lack of CD4+ or CD8+ single positive mature cells expressing the same TCR specificity in the periphery have led to the conclusion that deletion occurs at the CD4+ CD8+ double positive stage; however, there is no direct evidence demonstrating apoptotic CD4+ CD8+ cells in situ. Apoptosis of thymocytes in situ at other stages of T cell development has also not been reported. Using three-color immunofluorescence and flow cytometric assays on frozen human thymic tissue and freshly isolated human thymocytes respectively, we directly identify CD4+ CD8+ and CD4- CD8- thymocytes in newborn human thymus that contain intracellular fragmented DNA and are therefore apoptotic. We determine that 75% of the apoptotic thymocytes are CD4+ CD8+ double positive apoptotic thymocytes, and interestingly, that 13% are CD4- CD8- double negative thymocytes. The majority of apoptotic thymocytes in situ are detected at the cortical-medullary junction; however, apoptotic thymocytes are also found scattered throughout the cortex. Furthermore, we determine that within the apoptotic thymocyte population, 54% express the apoptotic regulatory protein bcl-2 in vivo, whereas 32% are bcl-2 negative. Thus, our in vivo data directly demonstrate that both CD4+ CD8+ and CD4- CD8- human thymocytes die in situ via an apoptotic process, and that expression of the bcl-2 protein in situ does not prevent immature thymocytes from apoptosis.

This article has been cited by other articles:

				R. J. McKallip, Y. Do, M. T. Fisher, J. L. Robertson, P. S. Nagarkatti, and M. Nagarkatti Role of CD44 in activation-induced cell death: CD44-deficient mice exhibit enhanced T cell response to conventional and superantigens Int. Immunol., September 1, 2002; 14(9): 1015 - 1026. [Abstract] [Full Text] [PDF]

				N. Moulian, F. Truffault, Y. M. Gaudry-Talarmain, A. Serraf, and S. Berrih-Aknin In vivo and in vitro apoptosis of human thymocytes are associated with nitrotyrosine formation Blood, June 1, 2001; 97(11): 3521 - 3530. [Abstract] [Full Text] [PDF]

				P. Bu, A. Keshavarzian, D. D. Stone, J. Liu, P. T. Le, S. Fisher, and L. Qiao Apoptosis: One of the Mechanisms That Maintains Unresponsiveness of the Intestinal Mucosal Immune System J. Immunol., May 15, 2001; 166(10): 6399 - 6403. [Abstract] [Full Text] [PDF]

				L. Crisa, V. Cirulli, K. A. Smith, M. H. Ellisman, B. E. Torbett, and D. R. Salomon Human Cord Blood Progenitors Sustain Thymic T-Cell Development and a Novel Form of Angiogenesis Blood, December 1, 1999; 94(11): 3928 - 3940. [Abstract] [Full Text] [PDF]

				J. E. Paz-Miguel, R. Flores, P. Sanchez-Velasco, G. Ocejo-Vinyals, J. Escribano de Diego, J. Lopez de Rego, and F. Leyva-Cobian Reactive Oxygen Intermediates During Programmed Cell Death Induced in the Thymus of the Ts(1716)65Dn Mouse, a Murine Model for Human Down's Syndrome J. Immunol., November 15, 1999; 163(10): 5399 - 5410. [Abstract] [Full Text] [PDF]

				K. K. Baldwin, P. A. Reay, L. Wu, A. Farr, and M. M. Davis A T Cell Receptor-specific Blockade of Positive Selection J. Exp. Med., January 4, 1999; 189(1): 13 - 24. [Abstract] [Full Text] [PDF]

				N. J. Olsen, S. M. Viselli, J. Fan, and W. J. Kovacs Androgens Accelerate Thymocyte Apoptosis Endocrinology, February 1, 1998; 139(2): 748 - 752. [Abstract] [Full Text] [PDF]

				D. M. Page, E. M. Roberts, J. J. Peschon, and S. M. Hedrick TNF Receptor-Deficient Mice Reveal Striking Differences Between Several Models of Thymocyte Negative Selection J. Immunol., January 1, 1998; 160(1): 120 - 133. [Abstract] [Full Text] [PDF]

				N. B. E. Oldenburg, R. B. Evans-Storms, and J. A. Cidlowski In Vivo Resistance to Glucocorticoid-Induced Apoptosis in Rat Thymocytes with Normal Steroid Receptor Function in Vitro Endocrinology, February 1, 1997; 138(2): 810 - 818. [Abstract] [Full Text] [PDF]