We show that developmental transitions during thymocyte maturation are associated with dramatic changes in chemotactic responses to chemokines. Macrophage-derived chemokine, a chemokine expressed in the thymic medulla, attracts thymocytes only during a brief window of development, between the late cortical and early medullary stages. All medullary phenotypes (CD4 or CD8 single positive) but not...

In vitro interactions of thymocytes and thymocyte hybridomas with cortical (R-TNC.1) and medullary (TE-R 2.5) rat thymic epithelial-cell (TEC) lines were studied. It was found that the cortical line had better adhesion capability. It bound exclusively immature CD4+ CD8+ alpha beta TCRlo thymocytes, induced apoptosis of a subset of these cells, and stimulated proliferation of the BWRT 1 (CD4- CD...

The thymic medulla plays a key role in negative selection (self-tolerance induction) and contains differentiated T cells en route to the extrathymic environment. However, being relatively mature, medullary T cells are thought to be beyond the stage of tolerance induction. This paradox is resolved by the finding that medullary T cells (CD4+8- thymocytes) comprise two distinct subsets. Medullary ...

Cyclosporin A (CsA), a potent inhibitor of T-cell activation, has been shown to have several effects on thymocyte maturation, thymic stromal cells, and the generation of autoreactive T cells. In Lewis rats, the combination of lethal irradiation, syngeneic bone marrow transplantation, and a 4-week course of CsA administration causes the development of an autoimmune disease (CsA-AI) resembling al...

The cellular and subcellular distribution of terminal deoxynucleotidyl transferase (DNA nucleotidylexotransferase; nucleosidetriphosphate:DNA deoxynucleotidylexotransferase, EC 2.7.7.31) in thymocytes and peripheral lymphocytes from rat, mouse, and calf was studied by immunofluorescence using rabbit antiserum to homogeneous transferase from calf. Terminal transferase was readily detected in app...

Intrathymic events in mice bearing methylcholanthrene induced fibrosarcoma (MBS-1) were examined using mainly flow cytometric analysis. Ten days after tumor inoculation, the number of whole thymocytes was remarkably decreased. Surface phenotypical analysis by flow cytometry showed that the proportion of thymocytes with a low density of peanut agglutinin (PNAlow thymocytes), which is about 30% i...

T he thymus is organized into discrete subcapsular, corti-cal, and medullary environments that have been defined by the distribution of morphologically and phenotyp-ically distinct populations of epithelial cells and other stromal cell constituents (1–5). T cell progenitor cells entering the thymus move in a centripetal fashion from the subcapsular region through the cortex to the medullary are...

The development of thymocyte subsets and of the thymic epithelium in SCID and RAG-2/-mice was monitored after normal bone-marrow-cell transfer. The kinetics of thymic reconstitution and their relationships with cell proliferation were investigated by using bromodeoxyuridine to detect DNA-synthesizing cells among lymphoid cells by 3-color flow cytometry, and in epithelial compartments by stainin...

Light microscopic and ultrastructural studies of thymus in wall lizard showed remarkable season dependent structural changes. In winter, the thymus was involuted and its cortico-medullary differentiation was not distinct. Thymocytes were sparsely distributed. The epithelial cells exhibited atrophic features such as an appreciable decrease in the nuclear-cytoplasmic ratio and accordingly reducti...

Prostaglandins (PGs) are lipid-derived mediators of rapid and localized cellular responses. Given the role of PG in supporting thymic T cell development, we investigated the expression of the PG synthases, also known as cyclooxygenases (COX)-1 and -2, in the biosynthesis of PGs in thymic stromal cell lines. The predominant isozyme expressed in cortical thymic epithelial cells was COX-1, while C...