title: A novel mechanism of complement-independent clearance of red cells deficient in glycosyl phosphatidylinositol-linked proteins.
abstract: Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic anemia characterized by the increased sensitivity of red blood cells (RBCs) to complement, leading to intravascular hemolysis and hemoglobinuria. PNH is due to the expansion of a cell clone that has acquired a mutation in the PIGA gene. Mice with targeted Piga gene inactivation genetically mimic the human disease and have phosphatidylinositol glycan class A-negative (PIGA-) RBCs with a reduced half-life in circulation. Although PIGA-RBCs are hypersensitive to complement in vitro, their complement sensitivity in vivo is barely detectable. Here we show that the shortened survival of PIGA- RBCs is independent of complement either by using inhibitory C5 antibodies or by transfusion into C5-, C4-, C3-, or factor B-deficient mice. Splenectomy or high-dose cortisone treatment had no effect on the shorter survival of PIGA- RBCs. However, treatment with liposome-encapsulated clodronate, an agent that depletes macrophages in vivo, normalized the half-life of PIGA- RBCs. This indicates that the shortened survival of PIGA- RBCs is due to a novel pathway of PIGA- RBC clearance that is mediated by macrophages, but occurs independently of complement. Future investigations will show whether this novel pathway of PIGA- RBC destruction identified in mice may also operate in patients with PNH.
authors.affiliation: Division of Hematology, Department of Internal Medicine, Washington University School of Medicine, St Louis, MO 63110, USA.
authors.forename: Marek
authors.initials: M
authors.lastname: Jasinski
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Pantazopoulos
authors.forename: Russell P
authors.initials: RP
authors.lastname: Rother
authors.forename: Nico
authors.initials: N
authors.lastname: van Rooijen
authors.forename: Wen-Chao
authors.initials: WC
authors.lastname: Song
authors.forename: Hector
authors.initials: H
authors.lastname: Molina
authors.forename: Monica
authors.initials: M
authors.lastname: Bessler
mesh_terms: D000743:Anemia, Hemolytic / Q000097:blood / Q000235:genetics; D000818:Animals; D003165:Complement System Proteins / Q000502:physiology*; D004195:Disease Models, Animal; D004912:Erythrocytes / Q000502:physiology*; D005434:Flow Cytometry; D017261:Glycosylphosphatidylinositols / Q000097:blood* / Q000172:deficiency*; D006207:Half-Life; D006457:Hemoglobinuria, Paroxysmal / Q000097:blood / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D051379:Mice; D009154:Mutation
chemical_list: D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; C080086:phosphatidylinositol glycan-class A protein; D003165:Complement System Proteins