title: The granzyme B inhibitor, protease inhibitor 9, is mainly expressed by dendritic cells and at immune-privileged sites.
abstract: Granzyme B is released from CTLs and NK cells and an important mediator of CTL/NK-induced apoptosis in target cells. The human intracellular serpin proteinase inhibitor (PI)9 is the only human protein able to inhibit the activity of granzyme B. As a first step to elucidate the physiological role of PI9, PI9 protein expression in various human tissues was studied. A mAb directed against human PI9 was developed, which specifically stained PI9-transfected COS-7 cells, and was used for immunohistochemistry. Both in primary lymphoid organs and in inflammatory infiltrates, PI9 was present in different subsets of dendritic cells. Also T-lymphocytes in primary and organ-associated lymphoid tissues were PI9 positive. Endothelial cells of small vessels in most organs tested as well as the endothelial layer of large veins and arteries showed strong PI9 staining. Surprisingly, high PI9 protein expression was also found at immune-privileged sites like the placenta, the testis, the ovary, and the eye. These data fit with the hypothesis that PI9 is expressed at sites where degranulation of CTL or NK cells is potentially deleterious.
authors.affiliation: Department of Pathology, Free University Hospital, Amsterdam, the Netherlands.
authors.forename: B A
authors.initials: BA
authors.lastname: Bladergroen
authors.forename: M C
authors.initials: MC
authors.lastname: Strik
authors.forename: N
authors.initials: N
authors.lastname: Bovenschen
authors.forename: O
authors.initials: O
authors.lastname: van Berkum
authors.forename: G L
authors.initials: GL
authors.lastname: Scheffer
authors.forename: C J
authors.initials: CJ
authors.lastname: Meijer
authors.forename: C E
authors.initials: CE
authors.lastname: Hack
authors.forename: J A
authors.initials: JA
authors.lastname: Kummer
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D000918:Antibody Specificity; D015153:Blotting, Western; D019556:COS Cells; D003713:Dendritic Cells / Q000276:immunology* / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000201:enzymology / Q000276:immunology; D005123:Eye / Q000201:enzymology / Q000276:immunology; D005260:Female; D053804:Granzymes; D006801:Humans; D008221:Lymphoid Tissue / Q000201:enzymology / Q000276:immunology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009928:Organ Specificity / Q000276:immunology*; D010053:Ovary / Q000201:enzymology / Q000276:immunology; D010920:Placenta / Q000201:enzymology / Q000276:immunology; D012697:Serine Endopeptidases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000096:biosynthesis* / Q000276:immunology / Q000502:physiology; D015843:Serpins / Q000096:biosynthesis* / Q000276:immunology / Q000502:physiology; D013737:Testis / Q000201:enzymology / Q000276:immunology; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; C102316:SERPINB9 protein, human; D015842:Serine Proteinase Inhibitors; D015843:Serpins; C509213:GZMB protein, human; D053804:Granzymes; C509214:Gzmb protein, mouse; D012697:Serine Endopeptidases