title: Transient expression of IL-2 receptor precedes the differentiation of immature thymocytes.
abstract: The growth of mature T lymphocytes after activation by antigen is regulated by the binding and endocytosis of interleukin-2 (IL-2). In the thymus, approximately 50% of adult thymocytes that carry neither the CD4 nor the CD8 antigen and day 14-15 fetal CD4-8- thymocytes express receptors for IL-2(IL-2R). The CD4-8- (double-negative) subpopulation of thymocytes contains the precursors of cells that can differentiate along an unknown pathway into thymocytes bearing either CD8 or CD4, with the characteristics of mature T lymphocytes. The basis for IL-2R expression by double-negative thymocytes is unclear as they appear to lack a functional T-cell receptor/CD3 complex through which activation of peripheral T cells is mediated. The argument for a role for IL-2 in thymocyte differentiation has also been complicated by conflicting reports on the inability or capability of double-negative thymocytes to respond to IL-2 in vitro. At present, both the nature of the stimuli within the thymic micro-environment which induce IL-2R expression and its relevance to thymocyte differentiation are not known. We show here that the IL-2R-bearing subset has a greater potential to differentiate into phenotypically mature T lymphocytes than do IL-2R-negative thymocytes. In addition, progeny of IL-2R-negative donor cells transiently express IL-2R in the thymuses of adoptive hosts before generating CD8 and/or CD4-positive thymocytes. These results identify the IL-2R-positive cells as a more differentiated double-negative thymocyte subset on the pathway to mature T lymphocytes.
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D005333:Fetus; D005434:Flow Cytometry; D007116:Immunization, Passive; D007376:Interleukin-2 / Q000276:immunology; D008198:Lymph Nodes / Q000276:immunology; D051379:Mice; D008815:Mice, Inbred Strains; D011971:Receptors, Immunologic / Q000096:biosynthesis*; D015375:Receptors, Interleukin-2; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology
chemical_list: D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2