Modulation of the granzyme B inhibitor proteinase inhibitor 9 (PI-9) by activation of lymphocytes and monocytes in vitro and by Epstein-Barr virus and bacterial infection.
Proteinase inhibitor 9 (PI-9) is an intracellular serpin expressed in lymphocytes and monocyte-derived cells. It is the only known endogenous natural antagonist of granzyme B (GrB), and its proposed function is protection of cells from misdirected GrB. We have studied the regulation of PI-9 in primary peripheral blood mononuclear cells (PBMCs) following ex-vivo stimulation, and in PBMCs from patients suffering from viral or bacterial infections. By intracellular flow cytometry, we found identical PI-9 expression in all lymphocyte subsets, lower levels in monocytes and none in granulocytes. PI-9 was stable for 48 h in the presence of cycloheximide, indicating slow protein turnover. Incubation of PBMCs with several stimuli including lipopolysaccharide (LPS) led to up-regulation in the monocyte, but not the lymphocyte fraction, within 48 h, inhibitable by the NF-kappaB inhibitor pyrrolidin dithiocarbamate (PTDC). Up-regulation of PI-9 was observed in lymphocytes and monocytes of patients with acute Epstein-Barr virus (EBV), but not bacterial infection. Preterm infants had similar PI-9 expression as adults in monocytes, but lower in lymphocytes, decreasing during bacterial infection. Taken together, our data indicate that PI-9 is rapidly up-regulated upon stimulation of monocytes, but not lymphocytes. By protecting monocytes and macrophages from misdirected GrB in the inflammatory process, PI-9 might be involved in the regulation of antigen presentation.
University Children's Hospital Ulm, Ulm, Germany. cfclassen@gmx.de
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D000208:Acute Disease; D000328:Adult; D001424:Bacterial Infections / Q000276:immunology*; D002478:Cells, Cultured; D002648:Child; D003907:Dexamethasone / Q000494:pharmacology; D020031:Epstein-Barr Virus Infections / Q000276:immunology*; D005434:Flow Cytometry; D005938:Glucocorticoids / Q000494:pharmacology; D006098:Granulocytes / Q000276:immunology; D053804:Granzymes; D006801:Humans; D007376:Interleukin-2 / Q000276:immunology; D008070:Lipopolysaccharides / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D016131:Lymphocyte Subsets / Q000276:immunology; D009000:Monocytes / Q000276:immunology; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D011759:Pyrrolidines / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000276:immunology*; D015842:Serine Proteinase Inhibitors / Q000096:biosynthesis / Q000097:blood*; D015843:Serpins / Q000096:biosynthesis / Q000097:blood*; D013859:Thiocarbamates / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology
D005938:Glucocorticoids; D007376:Interleukin-2; D008070:Lipopolysaccharides; D016328:NF-kappa B; D011759:Pyrrolidines; C102316:SERPINB9 protein, human; D015842:Serine Proteinase Inhibitors; D015843:Serpins; D013859:Thiocarbamates; C020972:pyrrolidine dithiocarbamic acid; D003907:Dexamethasone; C509213:GZMB protein, human; D053804:Granzymes; D012697:Serine Endopeptidases