title: Requirement for surface aminopeptidase activities during development of CD8+ fetal thymocytes.
abstract: The role of surface aminopeptidases (APs), enzymes that cleave amino-terminal residues from polypeptide chains, in the development of fetal thymocytes was studied using a murine fetal thymic organ culture (FTOC) model. FTOC AP activity was demonstrable for various amino acid-p-nitroanilide substrates, and specific inhibitors of AP (amastatin and bestatin) inhibited enzymatic activity. AP activity decreased from Day 4 to Day 7 in FTOC. Inhibition of AP activity during thymic development by FTOC in the presence of bestatin caused a significant selective decrease in the percentage of CD8+ cells (both CD4+CD8+ and CD4-CD8+). Bestatin did not downregulate expression of CD8 by a mature CD8+ T cell clone. These data suggest that APs are involved in the development of thymocytes expressing CD8.
authors.affiliation: University of Pittsburgh Cancer Institute and Department of Pathology, University of Pittsburgh, School of Medicine, Pennsylvania 15213, USA. gastrot@pitt.edu
authors.forename: P M
authors.initials: PM
authors.lastname: Appasamy
authors.forename: T W
authors.initials: TW
authors.lastname: Kenniston
authors.forename: A A
authors.initials: AA
authors.lastname: Amoscato
mesh_terms: D000626:Aminopeptidases / Q000037:antagonists & inhibitors / Q000502:physiology*; D000818:Animals; D015704:CD4 Antigens / Q000032:analysis; D016827:CD8 Antigens / Q000032:analysis; D018414:CD8-Positive T-Lymphocytes / Q000201:enzymology* / Q000502:physiology; D005260:Female; D005333:Fetus / Q000276:immunology*; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D009924:Organ Culture Techniques; D013950:Thymus Gland / Q000201:enzymology
chemical_list: D015704:CD4 Antigens; D016827:CD8 Antigens; D000626:Aminopeptidases