Immunoglobulin E oligomers identified in blood components activate mast cells: relevance to anaphylactic transfusion reaction

BACKGROUND: In most cases of anaphylactic transfusion reaction, the mechanisms underlying its development are unclear. We found a donor whose transfused blood components were implicated in two cases of anaphylactic transfusion reaction, and we found that the donor plasma showed mast cell degranulation activity. STUDY DESIGN AND METHODS: The donor plasma was examined to identify the mast cell–activating factors in it. Cultured mast cells prepared from cord blood were used for in vitro degranulation assay. Serum prepared from the donor plasma was fractionated by three-step chromatography using mast cell degranulation activity as a marker. The fractions selected from the third step of chromatography were analyzed by mass spectrometry after separation by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The characteristics of the identified proteins and other plasma samples that had been donated by the donor over several years were examined. RESULTS: Two plasma proteins of high molecular weight were detected in the anion-exchange fractions and identified as human immunoglobulin (Ig)Es of 500 kDa and higher. The mast cell degranulation activity of the IgEs decreased in the presence of monomeric human IgE as well as an anti-human IgE antibody. Mast cell degranulation activity was detected in the donor plasma since January 4, 2002, when the first case was reported. CONCLUSION: We identified high-molecular-weight IgEs as the mast cell–activating factors in the donor plasma. Results of analysis suggest that these IgEs were dimeric and trimeric and that they directly activated the transfusion recipient's mast cells by triggering the crosslinking of Fce receptor I, thereby inducing an anaphylactic transfusion reaction.