Background - Correct blood group typing is the cornerstone of transfusion medicine. In patients whose gastrointestinal wall is compromised, bacterial enzymes can cause deacetylation of blood group A, converting N-acetylgalactosamine to galactosamine, which resembles the B-defining galactose. This acquired B (acqB) phenomenon, first described 1959, can lead to blood grouping errors. Herein, we explore the possibility of producing acqB red blood cells (RBCs) by enzymatic conversion, for quality control purposes.
Materials and methods - A1 RBCs along with group B and O control RBCs were subjected to enzymatic digestion by bacterially derived deacetylase, FpGalNAcDeAc. RBCs were tested with monoclonal anti-A, anti-B, acquired-B-reactive anti-B (ES4 clone), and a panel of donor plasmas. Standard serological techniques were used. RBCs were subsequently frozen by a glycerolisation method, stored at −80 oC, and thawed for testing to evaluate stability.
Results - Specific deacetylation of A antigen was achieved at both enzyme concentrations. Enzymatically modified A1 RBCs reacted 1-3+ with clone ES4 but not with other anti-B reagents. Group B and O RBC controls reacted as expected. Crossmatch testing revealed 1-3+ reactions in 17/26 group A plasma with modified RBCs but not with untreated controls. Furthermore, 2/3 group AB plasmas reacted strongly with the modified RBCs. The acqB phenotype was maintained upon freezing/thawing.
Discussion - Using a recombinant deacetylase, we demonstrated the feasibility of creating acqB RBCs from donor A1 RBCs, thus providing a reagent for quality assurance of monoclonal anti-B. These RBCs can be frozen once treated, providing a reliable source of this unusual but clinically important phenotype.
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