title: Normal function of CR1 on affected erythrocytes of patients with paroxysmal nocturnal hemoglobinuria.
abstract: Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic anemia in which affected erythrocytes (E) are abnormally sensitive to lysis by autologous complement. Affected E from patients with PNH (PNH-E) are deficient in an E membrane regulatory protein of complement, decay-accelerating factor (DAF). Because a functional defect in a second membrane regulatory protein of complement, CR1 (C3b receptor), has also been hypothesized, severely affected PNH-E (type III PNH-E) were tested for abnormalities in CR1 by four methods. E from two patients with 100% type III PNH-E had 3201 and 6783 sites per cell for binding of 125I-labeled rabbit polyclonal F(ab')2 anti-CR1. These values fall within the normal range of CR1 antigenic sites per cell (1267 to 7915, mean = 5,014 +/- 155 SEM) established by assaying the E from 113 healthy donors. The Ka of CR1 on type III PNH-E for 125I-labeled C3b dimer was 2.06 X 10(7) M-1, and the Ka values for the binding of the same ligand to the E from two healthy individuals were 2.45 X 10(7) M-1 and 1.58 X 10(7) M-1. In an assay designed to measure the capacity of human E (Eh) to accelerate the decay of the classical C3 convertase deposited on 1 X 10(7) bystander sheep E (EAC1gp,4bh,2agp), the half-life (t 1/2) of this convertase was diminished from 18.1 min (range 15.2 to 22.9) to 8.1 min (range 7.4 to 8.5) by the addition of 1 X 10(7) normal Eh, to 6.2 min by 100% type III PNH-E, and to 7.5 min by Eh pretreated with an IgG fraction of human antiserum directed against the D antigen of the Rh system. In contrast, Eh (t 1/2 = 7.4) pretreated with a saturating dose of F(ab')2 anti-CR1, and CR1-deficient Eh (less than 10 CR1 molecules/E) from a patient with systemic lupus erythematosus, showed a loss of convertase decay-accelerating capacity to t 1/2 = 11.6 and t 1/2 = 12.4, respectively. Type III PNH-E pretreated with anti-CR1 demonstrated a total loss of their decay-accelerating capacity (t 1/2 = 19.9). In an assay of I cofactor activity, soluble C3b was rapidly converted to iC3b by purified I plus Eh or type III PNH-E, whereas CR1-deficient Eh exhibited less than 5% the I cofactor activity of normal Eh.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.forename: W N
authors.initials: WN
authors.lastname: Roberts
authors.forename: J G
authors.initials: JG
authors.lastname: Wilson
authors.forename: W
authors.initials: W
authors.lastname: Wong
authors.forename: D E
authors.initials: DE
authors.lastname: Jenkins
authors.forename: D T
authors.initials: DT
authors.lastname: Fearon
authors.forename: K F
authors.initials: KF
authors.lastname: Austen
authors.forename: A
authors.initials: A
authors.lastname: Nicholson-Weller
mesh_terms: D000936:Antigen-Antibody Complex; D003176:Complement C3 / Q000502:physiology*; D003179:Complement C3b / Q000502:physiology; D000939:Epitopes / Q000032:analysis; D004912:Erythrocytes / Q000276:immunology*; D006457:Hemoglobinuria, Paroxysmal / Q000276:immunology*; D006461:Hemolysis; D006801:Humans; D007106:Immune Sera; D007074:Immunoglobulin G / Q000276:immunology; D011951:Receptors, Complement / Q000502:physiology*; D017463:Receptors, Complement 3b
chemical_list: D000936:Antigen-Antibody Complex; D003176:Complement C3; D000939:Epitopes; D007106:Immune Sera; D007074:Immunoglobulin G; D011951:Receptors, Complement; D017463:Receptors, Complement 3b; D003179:Complement C3b