The frequency of phospholipase A(2) binding of basophilic granulocytes does not decrease during bee-venom-specific immunotherapy

Background: The major allergenic component of bee Venom is phospholipase A( 2) (PLA2). Methods: In this study, PLA2 was used to analyze and enrich PLA2-binding ce lls from peripheral blood by high gradient magnetic cell sorting. Results: In normal donors, the frequency of allergen (PLA2)-binding cells a mong peripheral blood mononuclear cells (PBMC) as determined by flow cytome try is below 0.1%, whereas in beevenom-allergic patients, PLA2-binding cell s are readily detectable at frequencies of up to 2.3%. In severely bee-veno m-allergic patients, many basophilic granulocytes are present, as defined b y anti-CD9, CD25, and CD38 mAb, comprising up to 95% of the PLA2-binding ce lls. From blood of allergic and normal donors, about equal absolute numbers of allergen-binding CD19/21-positive B cells can be enriched. Severe anaph ylactic reactions (Mueller grade IV) and failure of or adverse reactions du ring immunotherapy are associated with high numbers of circulating allergen -binding basophils. Interestingly, in the patients studied, the number of P LA2-binding basophilic granulocytes did not markedly change during rush imm unotherapy and up to 6 months of maintenance immunotherapy. Conclusions: The specific and reproducible enrichment of PLA2-binding cells provides a new tool for the analysis and monitoring of effector cells in b ee-venom-allergic patients with immediate-type hypersensitivity.