Subpopulations of fetal thymocytes defined by expression of T cell receptor/CD3 and IL-2 receptor. CD3 and IL-2 receptor alpha-chain are expressed on reciprocal cell populations.
The expression of the TCR/CD3 complex and the IL-2R alpha chain (p55) on fetal thymocytes has been analyzed by flow cytometry (FCM). Two-parameter immunofluorescence identified three subpopulations which were respectively IL-2R alpha-/CD3+, IL-2R alpha+/CD3-, or IL-2R alpha-/CD3-; no detectable population of IL-2R alpha+/CD3+ cells was found in unstimulated fetal thymocytes. Fractionation by "panning" and by sterile flow cytometric separation was used to characterize the functional responsiveness of these three subpopulations to a variety of stimuli. All three populations proliferated in response to PMA + ionomycin + rIL-2. In contrast, stimulation with anti-CD3 + IL-2 induced proliferation in IL-2R alpha-/CD3+ and IL-2R alpha-/CD3- but not in IL-2R alpha+/CD3- thymocytes. IL-2R alpha- cells, including sorted IL-2R alpha-/CD3- thymocytes, underwent a phenotypic change in response to in vitro stimulation with anti-CD3 + IL-2, resulting in the appearance of an IL-2R alpha+/CD3+ population that was not detected in freshly isolated thymocytes. The ability of fractionated fetal thymocytes to produce lymphokine in response to PMA + ionomycin was also evaluated. Only the IL-2R alpha-/CD3- fraction generated detectable IL-2. These findings demonstrate for the first time that CD3 and IL-2R alpha are expressed in a mutually exclusive fashion in fetal thymocytes and define three subpopulations of thymocytes that differ significantly in their proliferative and differentiative responses to TCR-mediated, IL-2R-mediated, and pharmacologic stimulation.
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Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
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Sharrow
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D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis*; D017252:CD3 Complex; D002454:Cell Differentiation; D002455:Cell Division; D005333:Fetus / Q000276:immunology; D005455:Fluorescent Antibody Technique; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000378:metabolism; D051379:Mice; D010641:Phenotype; D011948:Receptors, Antigen, T-Cell / Q000096:biosynthesis*; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis*; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology*; D013950:Thymus Gland / Q000196:embryology* / Q000276:immunology
D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D008222:Lymphokines; D011948:Receptors, Antigen, T-Cell; D015375:Receptors, Interleukin-2