α-Gal Sensitization in Group O Blood Recipients Linked to Severe Allergic Transfusion Reactions

α-Gal sensitization was first described in 2009. It occurs when individuals develop IgE antibodies against the common mammalian disaccharide galactose-α-1,3-galactose (α-Gal), which is often triggered by tick bites. A retrospective national study in France from 2022 to 2024 found that severe allergic reactions were higher in group O recipients transfused with group B or AB platelets and plasma compared to other ABO combinations, which led to the hypothesis that α-Gal sensitization in group O recipients could be contributing to these severe allergic transfusion reactions. α-Gal is immunogenically similar and cross-reactive with the blood group B glycan.  Recently, researchers in France grouped 59 platelet and plasma transfusion recipients who had severe allergic transfusion reactions (grade > 2) into three categories—group O recipients who received B or AB platelets or plasma (Group 1; n=12), group O recipients who received A plasma or platelets (Group 2; n=4), and all remaining recipients (Group 3; n=43). All patients were then tested for the presence of anti-α-Gal IgE antibodies of which 67% of Group 1 patients had high titers compared to zero in Group 2. In addition, 7% (3/43) of recipients in Group 3 had high titers of anti-α-Gal IgE antibodies, all of which were group O recipients who received group O products. Further investigations in other geographic regions are needed to confirm these observations, and care should be taken transfusing group O patients with incompatible plasma and platelets.

References:

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