title: Presence of C1-inhibitor polymers in a subset of patients suffering from hereditary angioedema.
abstract: Hereditary angioedema (HAE) is a potentially life-threatening disease caused by mutations in the gene encoding the serine protease inhibitor (serpin) C1 inhibitor (C1-inh). The mutations cause decreased functional plasma levels of C1-inh, which triggers unpredictable recurrent edema attacks. Subjects suffering from HAE have been classified in type I patients with decreased functional and antigenic levels of C1-inh, and type II patients with decreased functional but normal antigenic C1-inh levels. However, a few reports have demonstrated that some mutations cause C1-inh polymerization in vitro, and it is speculated that C1-inh polymers may exist in patient plasma, challenging the current classification of HAE patients. To investigate the presence of C1-inh polymers in patient plasma samples, we developed an immunological method, where monoclonal antibodies produced against polymerized C1-inh were applied in native PAGE western blotting. Using this approach we analyzed genuine plasma samples from 31 Danish HAE families, and found that plasma samples from three genotypically distinct HAE type I families (classified upon C1-inh plasma concentrations) contained C1-inh polymers. Identical C1-inh polymerization phenotypes were observed in four affected family members from one of these families. Genotyping of the families revealed that the polymerogenic mutations of two families were located in proximity to the reactive center loop insertion site in C1-inh (p.Ile271Thr and p.Ser258_Pro260del),and one mutation affected helix C (p.Thr167Asn). In conclusion, we demonstrate that C1-inh polymers are present in the plasma of a subgroup of HAE type I patients.
authors.affiliation: University of Southern Denmark, Institute of Public Health, Unit for Thrombosis Research, Esbjerg, Denmark.
authors.forename: Daniel Elenius
authors.initials: DE
authors.lastname: Madsen
authors.affiliation: University of Southern Denmark, Institute of Molecular Medicine, Cancer and Inflammation Research, Odense C, Denmark.
authors.forename: Søren
authors.initials: S
authors.lastname: Hansen
authors.affiliation: University of Southern Denmark, Institute of Public Health, Unit for Thrombosis Research, Esbjerg, Denmark.
authors.forename: Jørgen
authors.initials: J
authors.lastname: Gram
authors.affiliation: Hereditary Angioedema Centre Denmark, Department of Dermatology and Allergy Centre, Odense University Hospital, Odense C, Denmark.
authors.forename: Anette
authors.initials: A
authors.lastname: Bygum
authors.affiliation: University Joseph Fourier Grenoble, National Reference Centre for Angioedema, Grenoble, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Drouet
authors.affiliation: University of Southern Denmark, Institute of Public Health, Unit for Thrombosis Research, Esbjerg, Denmark.
authors.forename: Johannes Jakobsen
authors.initials: JJ
authors.lastname: Sidelmann
mesh_terms: D054179:Angioedemas, Hereditary / Q000097:blood* / Q000235:genetics; D000818:Animals; D016022:Case-Control Studies; D003174:Complement C1 Inactivator Proteins / Q000235:genetics / Q000378:metabolism*; D050718:Complement C1 Inhibitor Protein; D005260:Female; D006801:Humans; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D009154:Mutation; D066329:Protein Aggregates
chemical_list: D003174:Complement C1 Inactivator Proteins; D050718:Complement C1 Inhibitor Protein; D066329:Protein Aggregates; C469952:SERPING1 protein, human