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      Neonatal Androgenization Affects the Intrathymic T-Cell Maturation in Rats

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          Abstract

          The thymus structure, expression of CD4/CD8/TCRαβ on thymocytes and thymocyte proliferative and apoptotic indexes were analyzed in sexually immature 30-day-old and in sexually mature 60-day-old female rats neonatally androgenized (NA) by subcutaneous injection of 500 µg testosterone propionate/day on days 1–3 and in their vehicle-administered counterparts. The treatment affected normal thymus development. Thus, at 30 days of age, there was a reduction in the thymus weight, reflecting a decrease in the main thymic compartments. However, at 60 days of age, thymus weight did not significantly differ from that in age-matched controls, since the cortical volume enlargement was followed by a proportional decrease in the medullary volume. In rats of both ages, the changes in thymic compartments most likely reflected alterations in the size of both lymphoid and nonlymphoid components. Furthermore, in NA rats, substantial changes in thymocyte phenotypic characteristics were registered, in spite of their age. In both groups of NA rats, a decrease in the relative proportion of the least mature CD4–8–TCRαβ– cells and in that of CD4+8– TCRαβ–/TCRαβ<sup>low</sup> cells followed by an increase in the percentage of their successor CD4+8+TCRαβ–/TCRαβ<sup>low</sup> cells was detected. In addition, in 30-day-old NA rats, the relative proportions of CD4+8+TCRαβ<sup>high</sup> cells (just positively selected) and that of mature single positive (CD4+8– and CD4–8+) and CD4–8– double negative TCRαβ<sup>high</sup> cells, were reduced, while in 60-day-old NA rats only the percentage of CD4+8+TCRαβ<sup>high</sup> thymocytes was decreased. Thus, the study showed that the changes in the development of the hypothalamo-pituitary-gonadal axis induced by neonatal androgenization may affect the thymus development and intrathymic T-cell maturation.

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          Most cited references 36

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          Mapping Precursor Movement through the Postnatal Thymus Reveals Specific Microenvironments Supporting Defined Stages of Early Lymphoid Development

          Cellular differentiation is a complex process involving integrated signals for lineage specification, proliferation, endowment of functional capacity, and survival or cell death. During embryogenesis, spatially discrete environments regulating these processes are established during the growth of tissue mass, a process that also results in temporal separation of developmental events. In tissues that undergo steady-state postnatal differentiation, another means for inducing spatial and temporal separation of developmental cues must be established. Here we show that in the postnatal thymus, this is achieved by inducing blood-borne precursors to enter the organ in a narrow region of the perimedullary cortex, followed by outward migration across the cortex before accumulation in the subcapsular zone. Notably, blood precursors do not transmigrate the cortex in an undifferentiated state, but rather undergo progressive developmental changes during this process, such that defined precursor stages appear in distinct cortical regions. Identification of these cortical regions, together with existing knowledge regarding the genetic potential of the corresponding lymphoid precursors, sets operational boundaries for stromal environments that are likely to induce these differentiative events. We conclude that active cell migration between morphologically similar but functionally distinct stromal regions is an integral component regulating differentiation and homeostasis in the steady-state thymus.
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            A monoclonal antibody to a constant determinant of the rat T cell antigen receptor that induces T cell activation. Differential reactivity with subsets of immature and mature T lymphocytes

            mAb R73 detects a T cell-specific surface molecule consisting of two disulfide-linked subunits of 40 and 46 kD, respectively, on 97% of peripheral rat T cells, as defined by the OX-52 marker. Of the few OX- 52+ R73- cells, none are CD4+ but many express the CD8 antigen known to be present on rat NK cells. mAb R73 is mitogenic for unseparated spleen cells and for purified T cells. In the absence of non-T "accessory cells", stimulation by R73 requires artificial crosslinking of the mAb and is largely dependent on exogenous IL-2. Overnight incubation of purified T cells with crosslinked R73 mAb induces blastoid transformation, IL-2-R expression, and modulation of the R73 antigen. In the rat thymus, mature medullary cells express the R73 determinant at the same level as peripheral T cells, whereas 94% of CD4-CD8- thymocytes are R73-. The major CD4+8+ thymocyte population contains 25% R73- and 70% R73low cells. Thymocytes of the CD4-CD8+OX-44- subpopulation that are the direct precursors of CD4+CD8+ cells display a continuum of R73 antigen density from undetectable to very low levels. We conclude that R73 is most likely directed at a constant determinant of the rat alpha/beta heterodimeric TCR and suggest that CD8+ immature thymocytes are the first cells in the T cell differentiation pathway to express this molecule at their surface.
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              Disorganization and restoration of thymic medullary epithelial cells in T cell receptor-negative scid mice: evidence that receptor-bearing lymphocytes influence maturation of the thymic microenvironment.

              In order to assess the possible role of lymphoid cells in the development of thymic epithelium, we compared the organization and maturation of thymic epithelium in scid mice lacking T cell receptor (TcR)-positive cells with that in scid mice containing TcR+ cells. Immunohistologic examination revealed that thymi from TcR- scid mice were deficient in thymic medullary epithelial cells recognized by the monoclonal antibody ER-TR5, and that the few thymic medullary epithelial cells present were not organized into discrete medullary areas. In contrast, thymi from scid mice containing TcR+ cells possessed ER-TR5+ thymic medullary epithelial cells and these cells were organized normally into discrete medullary regions. Thus, normal organization and maturation of thymic medullary epithelial cells did not occur in the absence of TcR+ cells, but did occur upon introduction of TcR+ cells. We conclude that lympho-stromal cell interactions in the thymus are not unidirectional, and that a symbiotic relationship exists between maturing epithelial cells and developing lymphocytes.
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                Author and article information

                Journal
                NIM
                Neuroimmunomodulation
                10.1159/issn.1021-7401
                Neuroimmunomodulation
                S. Karger AG
                1021-7401
                1423-0216
                2005
                March 2005
                17 March 2005
                : 12
                : 2
                : 117-130
                Affiliations
                aImmunology Research Center ‘Branislav Janković’, Institute of Immunology and Virology ‘Torlak’, and bDepartment of Physiology, Faculty of Pharmacy, Belgrade, Serbia and Montenegro
                Article
                83584 Neuroimmunomodulation 2005;12:117–130
                10.1159/000083584
                15785114
                © 2005 S. Karger AG, Basel

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                Page count
                Figures: 5, Tables: 1, References: 63, Pages: 14
                Categories
                Original Paper

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