Recent progress in understanding of allergic transfusion reaction.

Allergic transfusion reactions (ATRs) are among the most common adverse nonhemolytic transfusion reactions. However, since ATR is diagnosed based only on clinical observations, contrary to other allergic diseases, the causal relationship between a given ATR and the corresponding transfusion remains ambiguous in most cases. Although the prevailing theory suggests that immunoglobulin E (IgE)-mediated type I allergies are the primary cause of ATRs, the IgE-mediated pathway has rarely been demonstrated. Furthermore, despite accumulating reports suggesting the role of allergic predispositions to food and inhaled antigens, the etiology of ATR has yet to be fully elucidated. The recent introduction of the basophil activation test (BAT) and passive immune BAT into transfusion medicine has provided novel insights into these issues.