title: Biphasic clearance of incompatible red blood cells through a novel mechanism requiring neither complement nor Fcγ receptors in a murine model.
abstract: BACKGROUND
  Antibody binding to red blood cells (RBCs) can induce potentially fatal outcomes, including hemolytic transfusion reactions (HTRs), hemolytic disease of the fetus and newborn, and autoimmune hemolytic anemia. The mechanism(s) of RBC destruction following antibody binding is typically thought to require complement activation and/or the involvement of Fcγ receptors (FcγRs). In the current report, we analyzed mechanisms of HTRs during incompatible transfusions of murine RBCs expressing human glycophorin A (hGPA) into mice with anti-hGPA.
  
  
  METHODS
  C3 and Fcγ receptor knockout, splenectomized, Fcγ receptor blocking antibody-treated, and clodronate-treated mice were passively immunized with anti-hGPA (10F7 or 6A7) and transfused with RBCs expressing the hGPA antigen. Posttransfusion blood and serum were collected and analyzed via flow cytometry and confocal microscopy.
  
  
  RESULTS
  This HTR model results in both rapid clearance and cytokine storm. Neither complement nor FcγRs were required for RBC clearance; in contrast, FcγRs were required for cytokine storm. Circulating aggregates of hGPA RBCs were visible during the HTR. Splenectomy and phagocyte depletion by clodronate had no effect on acute RBC clearance; however, incompatible RBCs reentered over 24 hours in clodronate-treated mice.
  
  
  CONCLUSIONS
  These data demonstrate a biphasic HTR, the first phase involving sequestration of incompatible hGPA RBCs and the second phase involving phagocytosis of sequestered RBCs. However, the mechanism(s) of phagocytosis in the second phase required neither C3 nor FcγRs. These findings demonstrate novel mechanistic biology of HTRs.
authors.affiliation: Center for Transfusion and Cellular Therapies, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, USA.
authors.forename: Justine S
authors.initials: JS
authors.lastname: Liepkalns
authors.forename: Eldad A
authors.initials: EA
authors.lastname: Hod
authors.forename: Sean R
authors.initials: SR
authors.lastname: Stowell
authors.forename: Chantel M
authors.initials: CM
authors.lastname: Cadwell
authors.forename: Steven L
authors.initials: SL
authors.lastname: Spitalnik
authors.forename: James C
authors.initials: JC
authors.lastname: Zimring
mesh_terms: D000818:Animals; D001787:Blood Group Incompatibility / Q000276:immunology* / Q000473:pathology; D001803:Blood Transfusion; D003176:Complement C3 / Q000235:genetics* / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D004912:Erythrocytes / Q000276:immunology* / Q000473:pathology; D005434:Flow Cytometry; D006021:Glycophorins / Q000235:genetics / Q000276:immunology; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010587:Phagocytosis / Q000276:immunology; D017452:Receptors, IgG / Q000235:genetics* / Q000276:immunology*; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013156:Splenectomy
chemical_list: D003176:Complement C3; D016207:Cytokines; C485701:Fcgr1 protein, mouse; C485700:Fcgr3 protein, mouse; C522404:Fcgr4 protein, mouse; D006021:Glycophorins; D017452:Receptors, IgG