Premium
IgG3 anti‐Kell allotypic variation results in differential antigen binding and phagocytosis
Author(s) -
Cen Selena Y.,
Holton Mairead B.,
Binnington Beth,
Denomme Gregory A.,
Howie Heather L.,
Lebedev Jen.,
Zimring James C.,
Branch Donald R.
Publication year - 2020
Publication title -
transfusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.045
H-Index - 132
eISSN - 1537-2995
pISSN - 0041-1132
DOI - 10.1111/trf.15663
Subject(s) - phagocytosis , antibody , flow cytometry , recombinant dna , hemolysis , monoclonal antibody , subclass , immunology , antigen , monocyte , microbiology and biotechnology , biology , chemistry , gene , biochemistry
BACKGROUND Human immunoglobulin G (hIgG) includes four different subtypes (IgG1, IgG2, IgG3, and IgG4). Due to genetic variations, each IgG subtype contains different isoallotypes. It was previously shown that a Food and Drug Administration–approved monoclonal anti‐IgG failed to recognize 2 of 15 recombinant, human IgG3 anti‐Kell (K1) isoallotypes (rIgG3‐03 and rIgG3‐13) by indirect antiglobulin test (IAT). STUDY DESIGN AND METHODS We expressed and purified 15 recombinant human rIgG3 anti‐K1 isoallotypes and investigated their antigen binding and ability to induce phagocytosis using homozygous (KK) and heterozygous (Kk) K1‐positive red blood cells (RBCs) by gel IAT, flow cytometry, and a monocyte monolayer assay (MMA) with peripheral blood monocytes and cultured inflammatory (M1) and anti‐inflammatory (M2) macrophages. RESULTS MMA results showed that differences in the Fc region of rIgG3 anti‐K1 led to distinctive phagocytic activity with both monocytes and M1 macrophages. rIgG3‐18 and rIgG3‐19 showed an enhanced ability to induce phagocytosis. Differences in Fc regions also led to variations in the number of antibodies bound to KK RBCs. Despite the differences in phagocytic activity, all 15 rIgG3 clones are predicted to induce clinically significant hemolysis if K1‐positive blood was transfused into patients. CONCLUSION These results argue that antiglobulin reagents that fail to detect isoallotype rIgG3‐03 or rIgG3‐13 could present a transfusion risk or lack of detection of a potentially clinically significant anti‐K1 in hemolytic disease of the fetus and newborn.