Removing IgG antibodies from intact red cells: comparison of acid and EDTA, heat, and chloroquine elution methods.
BACKGROUND
To accurately phenotype red cell from patients with a positive direct antiglobulin test (DAT), nonlytic elution procedures were assessed for their ability to dissociate IgG from antibody-coated red cells without altering red cell antigen expression.


METHODS
Antibodies coating red cells that were sensitized in vivo (warm-reactive autoantibodies: 8 patients) or in vitro (42 alloantibodies) were eluted by using glycine-HCl and EDTA (acid/ EDTA), heat (56 degrees C, 10 min), or chloroquine method.


RESULTS
Acid/EDTA elution gave the best results, reducing DAT positivity to microscopic levels or rendering the DAT negative in 48 of 50 instances, whereas 4 samples remained resistant to heat elution and 24 to chloroquine. Standard DAT agglutination scores demonstrated that both acid/EDTA and heat elution were superior to the chloroquine method (p < 0.0001). With the gel low-ionic-strength saline indirect antiglobulin test, acid/ EDTA was superior to heat (p < 0.001). Overall, acid/ EDTA elution dissociated more antibodies than heat (p < 0.0001), especially for Kell system (K, k, Kpa, Kpb) alloantibodies. Common red cell antigens, other than Kell system antigens, were unaffected by acid/EDTA elution. In contrast, the expression of most blood group antigens was diminished after heat elution. However, it was possible to type red cell antigens by using gel low-ionic-strength saline indirect antiglobulin tests or tube agglutination methods.


CONCLUSIONS
Although heat elution may be used on a limited basis, the acid/EDTA method appears to be the procedure of choice for typing red cell coated with warm-reactive IgG alloantibodies or autoantibodies.
Burin des Roziers
N
N
Etablissement de Transfusion Sanguine de Languedoc-Roussillon, Nimes, France.
Squalli
S
S
D000143:Acids / Q000494:pharmacology; D000906:Antibodies / Q000302:isolation & purification*; D001323:Autoantibodies / Q000302:isolation & purification; D002738:Chloroquine / Q000494:pharmacology; D003298:Coombs Test / Q000379:methods; D004492:Edetic Acid / Q000494:pharmacology; D004912:Erythrocytes / Q000276:immunology*; D006358:Hot Temperature; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D008722:Methods
D000143:Acids; D000906:Antibodies; D001323:Autoantibodies; D007074:Immunoglobulin G; D002738:Chloroquine; D004492:Edetic Acid