Effect of Sex Steroids on T Cell Differentiation and Maturation in the Thymus.

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For recent years we have shown not only the presence of receptors for sex steroids (SH), androgen, estrogen (E) and progestin (P) in the thymus tissue, but also the immunohistochemical localization of these receptors in reticuloepithelial (RE) cells within the tissue in which thymic hormone (thymulin) is also exclusively localized. These findings clearly mean that both SH-containing cells and thymulin producing cells are the same RE cells, suggesting that SH may mediate some immune functions of the thymus through its receptors within the RE cells which produce thymulin to lead T cell differentiation.Female mice of C57BL/6NJcl strain were used. They were either ovariectomized (OVX) alone, OVX-estrogen-treated, or OVX-thymulin-treated. The thymus tissues were excised from each animal, and offered for the following experiments ;1. Scatchard plot analysis for steroid receptors (SR), 2. immunohistochemical staining to localize SR and thymulin, and 3. FACscan analysis to classify T cell subp … More opulation.The mouse thymus possessed specific receptors for E (ER) and P (PR) with high affinities and low capacities. In the ER-stained section, the stained cells were mainly located in the medulla, with dendritic cell processes, presumably RE cells. The cells comprising Hassall's corpuscle were also stained receptor-positive. In the adjacent section, a large number of thymulin-stained cells were localized exclusively in the medulla, with dendritic cell processes, identical with ER-positive RE cells. The cells of Hassall's corpuscle were also thymulin-positive. Tentatively, these results clearly indicate that both ER-containing cells and thymulin-producing cells are the same RE cells, similar to those reported for the rat thymus. E-treatment brought about a striking decrease in thymic tissue weight, whereas thymulin-treatment caused a fairly remarkable increase in weight. In turn, the loss of tissue weight by E depended on a significant decrease in the immature double positive T cell subsets with only a slight increase in the helper/inducer T cells. On the contrary, the gain of tissue weight by thymulin depended on a significant increase in the helper/inducer T cell subsets with no change in other T cell subpopulations.From the present study, it is clearly indicated that E mediates immune function of the thymus through its receptor with in RE cells which produce thymulin to lead differentiation and maturation of T cells. Less