Changes in immunologic properties of group A RBCs during treatment with an A-degrading exo-alpha-N-acetylgalactosaminidase.
BACKGROUND
Blood group A RBCs theoretically can be converted to universal-donor group O cells by incubation with alpha-N-acetylgalactosaminidase (A-zyme). The purpose of this study was to compare the extent of A-zyme treatment required to abolish several immunologic responses of group B or O recipients to group A RBCs.


METHODS
A(1) RBCs were incubated for 2 hours at 37 degrees C in buffer alone (control) or with 0.1 to 5.0 units (U) of A-zyme per mL of packed cells. They were then tested for 1) immune adherence (% rosetting) and activation of monocytic cells (% erythrophagocytosis, TNFalpha production), 2) activation of immune hemolysis, and 3) hemagglutination with Dolichos biflorus lectin and pooled human anti-A serum.


RESULTS
A 2-hour incubation with < or =5.0 U of A-zyme per mL of packed cells abolished monocytic cell adherence and phagocytosis of group A(1) RBCs coated with IgG(3) A MoAb. Epitopes of A binding to IgG(3) anti-A A005 MoAb and BG-2 MoAb differed in A-zyme sensitivity. TNFalpha production in group B or O whole blood in response to the addition of A(1) cells varied, but it essentially was abolished when group A cells were treated with 0.1 to 1.0 U of A-zyme per mL of packed cells. A epitopes mediating immune hemolysis and hemagglutination with D. biflorus lectin were also cleaved by <5 U of A-zyme per mL of packed cells. In contrast, hemagglutination with polyclonal anti-A typing serum was diminished by only 1 to 2 serial titer dilutions.


CONCLUSIONS
A epitopes mediating immune hemolysis and immune adherence to and activation of monocytic cells are highly sensitive to A-zyme cleavage, as compared to those mediating hemagglutination with monoclonal and polyclonal anti-A.
Hoskins
L C
LC
Department of Medicine, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio. lch2@po.cwru.edu
Boulding
E T
ET
D000017:ABO Blood-Group System / Q000276:immunology*; D004912:Erythrocytes / Q000276:immunology*; D006388:Hemagglutinins / Q000187:drug effects; D006454:Hemoglobins / Q000187:drug effects / Q000378:metabolism; D006461:Hemolysis / Q000187:drug effects / Q000276:immunology; D006596:Hexosaminidases / Q000494:pharmacology*; D006801:Humans; D010587:Phagocytosis / Q000187:drug effects; D012397:Rosette Formation; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000187:drug effects; D048809:alpha-N-Acetylgalactosaminidase
D000017:ABO Blood-Group System; D006388:Hemagglutinins; D006454:Hemoglobins; D014409:Tumor Necrosis Factor-alpha; D006596:Hexosaminidases; C482722:NAGA protein, human; D048809:alpha-N-Acetylgalactosaminidase