title: Granzyme C supports efficient CTL-mediated killing late in primary alloimmune responses.
abstract: It is well established that granzymes A and B play a role in CTL killing of target cells by the perforin-dependent granule exocytosis pathway. The functions of multiple additional granzymes expressed in CTL are less well defined. In the present studies, CTL generated from mice deficient in dipeptidyl peptidase 1 (DPP1) were used to investigate the contribution of granzyme C to CTL killing of allogeneic target cells. DPP1 is required for activation of granzymes A and B by proteolytic removal of their N-terminal dipeptide prodomains while a significant portion of granzyme C is processed normally in the absence of DPP1. Cytotoxicity of DPP1(-/-) CTL generated in early (5-day) MLC in vitro and in peritoneal exudate cells 5 days after initial allogeneic sensitization in vivo was significantly impaired compared with wild-type CTL. Following 3 days of restimulation with fresh allogeneic stimulators however, cytotoxicity of these DPP1(-/-) effector cells was comparable to that of wild-type CTL. Killing mediated by DPP1(-/-) CTL following restimulation was rapid, perforin dependent, Fas independent and associated with early mitochondrial injury, phosphatidyl serine externalization, and DNA degradation, implicating a granzyme-dependent apoptotic pathway. The increased cytotoxicity of DPP1(-/-) CTL following restimulation coincided with increased expression of granzyme C. Moreover, small interfering RNA inhibition of granzyme C expression during restimulation significantly decreased cytotoxicity of DPP1(-/-) but not wild-type CTL. These results indicate that during late primary alloimmune responses, granzyme C can support CTL-mediated killing by the granule exocytosis pathway in the absence of functional granzymes A or B.
authors.affiliation: Department of Internal Medicine, Division of Digestive and Liver Diseases, niversity of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Yonas
authors.initials: Y
authors.lastname: Getachew
authors.forename: Heather
authors.initials: H
authors.lastname: Stout-Delgado
authors.forename: Bonnie C
authors.initials: BC
authors.lastname: Miller
authors.forename: Dwain L
authors.initials: DL
authors.lastname: Thiele
mesh_terms: D000818:Animals; D020789:Cathepsin C / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D005089:Exocytosis / Q000235:genetics / Q000276:immunology*; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics / Q000276:immunology; D053804:Granzymes / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D007519:Isoantigens / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D054353:Perforin / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D010718:Phosphatidylserines / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000235:genetics; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology / Q000276:immunology*; D013997:Time Factors; D019014:fas Receptor / Q000235:genetics / Q000276:immunology / Q000378:metabolism
chemical_list: C491899:Fas protein, mouse; D007519:Isoantigens; D010718:Phosphatidylserines; D019014:fas Receptor; D054353:Perforin; D020789:Cathepsin C; D053804:Granzymes; C509214:Gzmb protein, mouse; C509216:Gzmc protein, mouse