High sensitivity of basophils predicts side-effects in venom immunotherapy

Background: Systemic side-effects of venom immunotherapy (VIT) represent a considerable problem in the treatment of patients allergic to Hymenoptera venom. We examined the hypothesis whether basophil responsiveness might be connected with the adverse reactions to VIT. Methods: Basophil surface expression of activation marker CD63 induced by different concentrations of honeybee and wasp venom (0.1 and 1 mu g/ml) was measured by flow cytometry in 34 patients with history of systemic anaphylactic reactions to Hymenoptera sting just before rush honeybee or wasp VIT. Results: Eleven of 34 patients had systemic anaphylactic reaction (Mueller grades I-III) and one patient a large local reaction to VIT. In those 12 patients, median percentage of activated basophils after stimulation with VIT-specific venom in concentration of 0.1 mu g/ml was 99% (range: 17-195) of value reached with stimulation with 1 mu g/ml. Side-effects occurred in all patients with 0.1/1 ratios over 92% (eight of 12). In contrast, in 22 patients with no side-effects, the median 0.1/1 ratio was 25% (range: 2-92). These concentration-dependent activation ratios were significantly different between the groups with and without side reactions (P < 0.0001). We also show significant positive correlation of the occurrence/clinical grade of the side-effects with individual ratios of CD63 basophil response (r = 0.73, P < 0.0001). Conclusion: The results suggest that increased basophil sensitivity to allergen-specific in vitro stimulation is significantly associated with major side-effects of VIT.