NA1/NA2 antisera inhibit FcgammaRI- but not FcgammaRII- mediated phagocytosis.
OBJECTIVE
Alloantibodies against the granulocyte-specific NA antigens play an important role in alloimmune neonatal neutropenia. As the NA system is located on the FcgammaRIIIb, the influence of NA-specific antibodies on granulocyte function is of special interest.


METHODS
We tested alloantisera specific for NA1 and NA2 for their ability to influence FcgammaR-mediated phagocytosis of polymorphonuclear neutrophils by use of different FcgammaR-specific targets. Red blood cells coated with human IgG anti-D served as specific targets for FcgammaRI-mediated phagocytosis while mouse IgG1 anti-glycophorin A was used to coat red blood cells (RBCs) to obtain FcgammaRII specific targets. To test for a hypothetical induction of phagocytosis by FcgammaRIIIb we used D-- RBCs coated with human monoclonal anti-D as target cells for unprimed neutrophils.


RESULTS
Granulocyte phagocytosis was directly induced by FcgammaRI and FcgammaRII but not by FcgammaRIIIb. NA1 alloantisera significantly inhibited FcgammaRI-mediated phagocytosis of IFN-gamma-stimulated neutrophils if the corresponding antigen was expressed. Conversely, NA2 alloantisera inhibited FcgammaRI-mediated phagocytosis in NA2-positive individuals. There was no effect of NA1- and NA2-specific alloantibodies on FcgammaRII-mediated phagocytosis.


CONCLUSIONS
NA-specific alloantisera inhibit the FcgammaRI-induced phagocytosis in primed neutrophils, but they do not significantly inhibit their FcgammaRIIa-specific phagocytosis of mIgG1-coated RBCs.
Flesch
B K
BK
Institute of Transfusion Medicine, University of Kiel, Germany. flesch@transfusion.uni-kiel.de
Maass
W
W
Neppert
J
J
D000328:Adult; D000818:Animals; D004912:Erythrocytes; D006021:Glycophorins / Q000276:immunology; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology*; D007074:Immunoglobulin G / Q000276:immunology; D007518:Isoantibodies / Q000276:immunology; D007519:Isoantigens / Q000276:immunology*; D051379:Mice; D009504:Neutrophils / Q000276:immunology*; D010587:Phagocytosis / Q000276:immunology*; D017452:Receptors, IgG / Q000037:antagonists & inhibitors* / Q000145:classification / Q000276:immunology / Q000502:physiology; D018029:Rho(D) Immune Globulin
D006021:Glycophorins; D007106:Immune Sera; D007074:Immunoglobulin G; D007518:Isoantibodies; D007519:Isoantigens; C061961:RHO(D) antibody; D017452:Receptors, IgG; D018029:Rho(D) Immune Globulin; C067704:neutrophil-specific antigen NA1, human; C072753:neutrophil-specific antigen NA2