title: Complement-mediated clearance of erythrocytes: mechanism and delineation of the regulatory roles of Crry and DAF. Decay-accelerating factor.
abstract: The role of complement in the pathogenesis of autoimmune hemolytic anemia (AIHA) has been controversial and may depend on a number of factors, including the affinity and isotype of the pathogenic antibodies involved. We have recently shown that mouse erythrocytes deficient in the membrane C3 regulatory protein, complement receptor 1-related gene/protein y (Crry), but not decay-accelerating factor (DAF), were spontaneously eliminated in vivo by complement. Here, by generating a mouse deficient in both DAF and Crry, we further delineated the roles of Crry and DAF in regulating alternative and classical pathway C3 activation. By using immunoglobulin-, Fcgamma receptor (FcgammaR)-, C3-, C4-, and C5-deficient mice, we also determined the mechanism by which membrane C3 regulator-deficient erythrocytes are cleared from the circulation. Finally, we evaluated the relative importance of the Fc receptor versus the complement pathway in disposing antibody-opsonized DAF/Crry-deficient erythrocytes. We conclude that (1) Crry plays a more dominant role than DAF in regulating the alternative pathway of complement, whereas DAF and Crry are equally effective in preventing antibody-induced runaway complement activation on mouse erythrocytes; (2) DAF/Crry-deficient erythrocytes are eliminated by the alternative pathway of complement via complement receptor-mediated erythrophagocytosis in the spleen; and (3) when opsonized with an immunoglobulin G2a (IgG2a) autoantibody, Crry/DAF-deficient erythrocytes are eliminated more rapidly by complement than by the Fc receptor pathway. These results shed new light on the relative activities of Crry and DAF and underscore the critical roles of membrane C3 regulators in preventing spontaneous and antibody-induced erythrocyte damage in vivo.
authors.affiliation: Center for Experimental Therapeutics, Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
authors.forename: Hector
authors.initials: H
authors.lastname: Molina
authors.forename: Takashi
authors.initials: T
authors.lastname: Miwa
authors.forename: Lin
authors.initials: L
authors.lastname: Zhou
authors.forename: Brendan
authors.initials: B
authors.lastname: Hilliard
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Mastellos
authors.forename: Michael A
authors.initials: MA
authors.lastname: Maldonado
authors.forename: John D
authors.initials: JD
authors.lastname: Lambris
authors.forename: Wen-Chao
authors.initials: WC
authors.lastname: Song
mesh_terms: D000361:Agammaglobulinemia / Q000097:blood / Q000235:genetics / Q000276:immunology; D000744:Anemia, Hemolytic, Autoimmune / Q000097:blood / Q000276:immunology; D000818:Animals; D001323:Autoantibodies / Q000276:immunology; D018958:CD55 Antigens / Q000235:genetics / Q000502:physiology*; D003176:Complement C3 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D003181:Complement C4 / Q000172:deficiency / Q000235:genetics; D003182:Complement C5 / Q000172:deficiency / Q000235:genetics; D003170:Complement Pathway, Alternative / Q000502:physiology*; D003171:Complement Pathway, Classical / Q000502:physiology*; D004789:Enzyme Activation; D004905:Erythrocyte Aging; D017707:Erythrocyte Transfusion; D006085:Graft Survival; D006461:Hemolysis / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009895:Opsonin Proteins / Q000276:immunology; D010587:Phagocytosis; D011951:Receptors, Complement / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D017463:Receptors, Complement 3b; D017452:Receptors, IgG / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D013154:Spleen / Q000166:cytology
chemical_list: D001323:Autoantibodies; D018958:CD55 Antigens; D003176:Complement C3; D003181:Complement C4; D003182:Complement C5; C081470:Cr1l protein, mouse; D009895:Opsonin Proteins; D011951:Receptors, Complement; D017463:Receptors, Complement 3b; D017452:Receptors, IgG