Reticuloepithelial Cells Research Articles

Development of the embryonic chicken thymus: II. Differentiation of the epithelial cells studied by electron microscopy

The differentiation of thymic epithelial cells in embryonic chickens was studied ultrastructurally from the tenth day of incubation to hatching. Reticuloepithelial cells first displayed functionally differentiated features between the twelfth and thirteenth days of incubation, whereas medullary epithelial cells with cysts and/or numerous granules did not display such features until the fifteenth day of incubation or later. Between the twelfth and thirteenth days, reticuloepithelial cells came to possess characteristic electron-lucent vacuoles and dense bodies. Furthermore, some of the vacuoles, probably as a result of fusion, seemed to contain the electron-dense bodies. The density of the material of such inclusion vacuoles tended to decrease after its entrance into the vacuoles. These findings suggested that the material in the inclusion vacuoles may be released into cytoplasm and, thereafter, may be secreted to exterior of the cells. Since a series of distinct morphological changes of reticuloepithelial cells took place simultaneously with an abrupt increase of lymphoctes bearing the embryonic thymus-specific antigen (T antigen), it is likely that the material supposedly released from the inclusion vacuoles of reticuloepithelial cells could be responsible for differentiation of lymphoid cells into embryonic T-antigen-bearing lymphocytes.

Effects of antithymic reticuloepithelial cells serum on the levels of circulating thymic factor and on the sensitivity to azathioprine of spleen spontaneous rosette-forming cells.

Swiss mice treated with an antithymic reticuloepithelial cells serum (ATRES) showed a drastic and prolonged depression of the serum thymic factor. A similar but less pronounced effect was also observed following the administration of the antithymocyte (ATS) and the antilymphocyte (ALS) sera. Conversely, the azathioprine sensitivity of spleen spontaneous rosette-forming cells was highly modified by the ATRES but not by the ATS or the ALS. The probable mechanisms of such effects are discussed.

Identification and separation of pre T-cells from nu/nu mice: Differentiation by preculture with thymic reticuloepithelial cells

Spleens and lymph nodes of nu/nu, congenitally athymic, mice have 16–32% and 72–76%, respectively, of large, brain-associated-T (BAT) antigen positive cells. These BAT positive large cells were isolated from nu/nu spleens with a fluorescence-activated cell sorter (FACS-II) and then cultured on thymic reticuloepithelial cell (TRC) monolayers. Both concanavalin A and mixed lymphocyte reactivity was induced during this culture period. We concluded that these BAT positive cells are pre-T cells which can he induced to at least some T cell functions by an inductive factor produced by TRC.

Cellular localisation and antigenic species specificity of thymic factors.

IT is now generally accepted that T-cell differentiation is influenced by several thymic factors1,2 and that thymic reticuloepithelial cells are responsible for the production of these factors. Antibodies to a soluble thymic factor (STF) have been reported to inhibit T-cell differentiation in chicken3 and anti-thymosin globulin has been shown to inhibit the recovery of T cells in ATS-treated mice4. Such antibodies therefore can be used to advantage in studies on the modulation of T-cell functions; in this context, a preliminary knowledge of the antigenic species specificity of thymic factors becomes a primary concern.

Specific Antigenicity of Thymic Reticuloepithelial Cells

Summary An antiserum was produced in rabbits against a lymphocyte-free extract of chicken thymus. After appropriate absorptions, the serum reacted by immunofluorescence only with thymic reticuloepithelial cells and with perinuclear areas in the cortex.

Effects of Antithymus Serum on Thymic Lymphopoiesis: A Radioautographic Study

Abstract In an attempt to investigate immunosuppressive mechanisms of antithymus serum, especially its superiority to antilymphocyte serum as immunosuppressive agents, the effects of these antisera on thymic lymphopoiesis were studied by radioautography. In rats treated with antithymus serum, thymidine incorporation by the thymic cortical lymphocytes was markedly suppressed although the number of thymidinelabeled lymphocytes appeared to be increased in the medulla and in the perivascular sheaths. In rats treated with antilymphocyte serum, on the other hand, there was increased thymidine incorporation by the cortical lymphocytes as indicated by the higher percentage of thymidine-labeled cells, the greater mean thymus weight and the histologic evidence. Despite lowered thymidine uptake, uridine uptake by the thymus cells of rats treated with antithymus serum was increased, suggesting an increased RNA metabolism in these cells. Histologically the majority of uridinelabeled cells were reticulo-epithelial cells and were mostly located in the medulla and in the perivascular sheaths, but some of them were seen in the subcapsular regions of the cortex showing positive periodic acid Schiff (PAS) stain. These findings suggest that the greater immunosuppressive potency of antithymus serum than that of antilymphocyte serum is related to the former's ability to suppress proliferation of the thymic cortical lymphocytes, possibly by inactivating a thymic humoral factor, whereas the latter serum has no such suppressive effect. Increased uridine uptake by the thymus of the animals treated with antithymus serum may indicate a compensatory increase in the production of a thymic humoral factor by the reticulo-epithelial cells.