Thymic Medulla Epithelial Cells Acquire Specific Markers by Post-Mitotic Maturation |
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Authors: | Claude Penit Bruno Lucas Florence Vasseur Theresa Rieker Richard L Boyd |
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Institution: | 1. INSERM U. 345, Institut Necker, 156 rue de Vaugirard, Paris Cedex 15, 75730, France.;2. Institute for General and Experimental Pathology, University of Innsbruck, Innsbruck, A-6020, Austria.;3. Department of Pathology and Immunology, Monash Medical School, Commercial Road, Prahran, Melbourne, Victoria, Australia, |
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Abstract: | The development of thymocyte subsets and of the thymic epithelium in SCID and RAG-2-/– mice was monitored after normal bone-marrow-cell transfer. The kinetics of thymic
reconstitution and their relationships with cell proliferation were investigated by using
bromodeoxyuridine to detect DNA-synthesizing cells among lymphoid cells by 3-color
flow cytometry, and in epithelial compartments by staining frozen sections. Thymocytes
started to express CD8 and CD4 10 days after transfer, simultaneously with extensive proliferation.
The first mature CD4+ single-positive cells were generated, from resting CD4+CD8+
cells after day 15. During this day 10–15 period, many epithelial cells positive for cortexspecific
or panepithelial markers were labeled with BrdUrd after pulse-injection. Organized
medullary epithelium also developed after day,15, that is, synchronously with the
appearance of mature thymocytes, but medullary cells were never found BrdUrd+. These
results suggest that, in these models, the reconstitution of the thymic epithelial network
proceeds through expansion of preexisting cortical or undifferentiated cells and by later
maturation (acquisition of specific markers) of medullary cells. This last process is dependent
of the presence of mature thymocytes. |
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Keywords: | Thymus epithelium thymocytes cell proliferation bone-marrow transfer RAG-2-/– mice |
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