Recombinant human immunoglobulin (Ig)A1 and IgA2 anti-D used for detection of IgA deficiency and anti-IgA.
BACKGROUND
To avoid anaphylactic reactions, immunoglobulin (Ig)A-deficient patients with anti-IgA should be transfused with IgA-deficient blood components. There is a need for fast and robust assays for demonstration of IgA deficiency and for detection of anti-IgA.


METHODS
Recombinant human IgA1 and IgA2 anti-D molecules were constructed, expressed in Chinese hamster ovary cells, and purified. These antibodies were used to sensitize group O D+ red blood cells (RBCs) for use as indicator cells, either in the format of a passive hemagglutination inhibition assay for detection of IgA deficiency or in a passive hemagglutination assay for detection of anti-IgA. Both assays were performed in gel card.


RESULTS
The sensitivity for IgA detection was adjusted to approximately 100 ng per mL. The assay for demonstration of IgA deficiency correlated with an enzyme-linked immunosorbent assay for quantification of IgA. Anti-IgA were easily detected, and the reactivity with IgA anti-D-sensitized RBCs could be inhibited by purified IgA1 and/or IgA2 and by normal plasma containing IgA but not by IgA-deficient plasma. Anti-IgA was found in 64 percent of IgA-deficient donors with less than 3 ng of IgA per mL.


CONCLUSIONS
The assays for detection of IgA and anti-IgA described in this article are fast and robust. Furthermore, they are applicable in all standard blood typing laboratories and are therefore well suited for immediate investigation of transfusion reactions.
Nielsen
Leif K
LK
Blood Bank, KI2034, Department of Clinical Immunology, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark. lkn@rh.regionh.dk
Dziegiel
Morten H
MH
D000888:Antibodies, Anti-Idiotypic / Q000032:analysis* / Q000276:immunology; D001803:Blood Transfusion; D004797:Enzyme-Linked Immunosorbent Assay; D006386:Hemagglutination Tests; D006801:Humans; D017098:IgA Deficiency / Q000175:diagnosis / Q000276:immunology*; D007070:Immunoglobulin A / Q000235:genetics / Q000276:immunology*; D011994:Recombinant Proteins / Q000032:analysis / Q000276:immunology
D000888:Antibodies, Anti-Idiotypic; D007070:Immunoglobulin A; D011994:Recombinant Proteins; C049937:anti-IgA