Impact of immunotherapy on blood dendritic cells in patients with Hymenoptera venom allergy

Background Modulation of T-cell differentiation, which is controlled by dendritic cells (DCs), plays a crucial role in specific immunotherapy (SIT). However, the number and the characteristics of blood DCs before and during immunotherapy are unknown. Objective To analyze the number and the characteristics of blood DC subsets in patients with Hymenoptera venom allergy before and after initiation of SIT. Methods In this clinical trial (NCT00947908), blood myeloid and plasmacytoid DCs were analyzed in 20 patients with Hymenoptera venom allergy (bee or wasp venom) by using 4-color flow cytometry at 3 time points: directly before SIT, and 52 hours and 12 months after initiation of SIT. In addition, 20 age-matched and sex-matched controls were examined. Results In patients with Hymenoptera venom allergy, the number of plasmacytoid DCs before SIT was comparable to that of controls. Plasmacytoid DCs decreased markedly 52 hours after initiation of SIT and returned to control levels after 12 months of treatment. Myeloid DCs were elevated in patients with Hymenoptera venom allergy before, during, and after the first 12 months of SIT. In addition, there were changes in the expression of function-associated surface molecules on myeloid DCs (such as Fc γ receptor 2 and Toll-like receptor 2) during SIT. Conclusion Numbers of blood myeloid DCs are elevated in patients with Hymenoptera venom allergy, and there are specific changes in the expression of function-associated surface molecules on these cells during SIT. Numbers of plasmacytoid DCs in blood are profoundly but are only transiently decreased after initiation of SIT.