IMMUNOHEMATOLOGY Recombinant human immunoglobulin (Ig)A1 and IgA2 anti-D used for detection of IgA deficiency and anti-IgA Leif K. Nielsen and Morten H. Dziegiel BACKGROUND: To avoid anaphylactic reactions, immunoglobulin (Ig)A-deficient patients with anti-IgA should be transfused with IgA-deficient blood compo- nents. There is a need for fast and robust assays for demonstration of IgA deficiency and for detection of anti-IgA. STUDY DESIGN AND METHODS: Recombinant human IgA1 and IgA2 anti-D molecules were con- structed, 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 con- taining 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. CONCLUSION: 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. I n healthy blood donors, the prevalence of selective immunoglobulin A (IgA) deficiency varies from approximately 1 in 330 in a North American popu- lation 1 to approximately 1 in 18,500 in Japan. 2 The majority of IgA-deficient individuals are asymptomatic, but there is a higher prevalence of respiratory and gas- trointestinal tract infections in IgA-deficient individuals. 3 Anti-IgA in an IgA-deficient recipient can cause transfu- sion reactions presenting as anaphylactic shock if the recipient is transfused with blood components containing IgA. To avoid this, patients with anti-IgA should be trans- fused with IgA-deficient blood components.To investigate transfusion reactions, and for identification and release of IgA-deficient components for these patients, fast, simple, and sensitive IgA and anti-IgA detection methods are needed. Several methods for demonstration of IgA defi- ciency and for detection of anti-IgA have been published, ABBREVIATIONS: rIgA1 = recombinant human immunoglobu- lin A1 anti-D; rIgA2 = recombinant human immunoglobulin A2m(1) anti-D; rIgG1 = recombinant human immunoglobulin G1 anti-D; rIgG3 = recombinant human immunoglobulin G3 anti-D. From the Blood Bank, KI2034, Department of Clinical Immunol- ogy, Copenhagen University Hospital (Rigshospitalet), Copen- hagen, Denmark. Address reprint requests to: Leif Kofoed Nielsen, Blodban- ken KI2034, Department of Clinical Immunology, Copenhagen University Hospital (Rigshospitalet), Blegdamsvej 9, DK-2100 Copenhagen, Denmark; e-mail: lkn@rh.regionh.dk. This work was supported by the Danish Medical Research Council, the Velux Foundation, the Novo Nordisk Research Foundation, Danmarks Frivillige Bloddonorer, Direktør Ib Hen- riksens Fond, The Danish Hospital Foundation for Medical Research, Region of Copenhagen, The Faroe Islands and Green- land, the EU BioMed program Contract Number BMH4-CT96- 1545, and Toyota Fonden, Denmark. Received for publication December 29, 2007; revision received March 5, 2008, and accepted March 10, 2008. doi: 10.1111/j.1537-2995.2008.01781.x TRANSFUSION 2008;48:1892-1897. 1892 TRANSFUSION Volume 48, September 2008