101. Activity of neutral endopeptidase and aminopeptidase N in mouse thymic stromal cells which bind double-positive thymocytes.
- Author
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Small M, Kaiser M, Tse W, Heimfeld S, and Blumberg S
- Subjects
- Amino Acid Sequence, Animals, Anti-Bacterial Agents pharmacology, Cell Differentiation, Cell Line, Transformed, Connective Tissue metabolism, Flow Cytometry, Immunophenotyping, Leucine analogs & derivatives, Leucine pharmacology, Mice, Mice, Inbred C3H, Mice, Inbred C57BL, Mice, Transgenic, Molecular Sequence Data, Neprilysin antagonists & inhibitors, Protease Inhibitors pharmacology, T-Lymphocyte Subsets immunology, Thymus Gland immunology, CD13 Antigens metabolism, CD4 Antigens analysis, CD8 Antigens analysis, Connective Tissue enzymology, Neprilysin metabolism, Peptides, T-Lymphocyte Subsets metabolism, Thymus Gland cytology
- Abstract
The activity of two peptidases was determined in immortalized lines of thymic stromal cells. A line of total stromal cells (T-TG-St) was grown from transgenic mouse expressing temperature-sensitive SV40 T antigen under the control of the regulatory elements of the mouse major histocompatibility complex class I gene. From these cells we isolated a subset (DP-TG-St) that binds thymocytes which are mainly CD4+8+. We also assayed a clone of fetal thymic epithelial cells (BA/10) that binds CD4+8+ thymocytes. Both lines of double -positive cell-binding stroma exhibited strong activity of two peptidases, neutral endopeptidase (NEP; EC 3.4.24.11) and aminopeptidase N (APN; EC 3.4.11.2). In contrast, the activity of both enzymes was very low in the total thymic stromal line. Use of the specific inhibitors confirmed that these two enzymes were responsible for the activity observed but also suggested the presence of additional unidentified aminopeptidase(s) in the same stromal cells. The high activity of the two peptidases on stromal cells that bind thymocytes at the double-positive stage raises the possibility that they might contribute to the microenvironment of the developing thymocytes.
- Published
- 1996
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