Decreased release of histamine and sulfidoleukotrienes by human peripheral blood leukocytes after wasp venom immunotherapy is partially due to induction of IL-10 and IFN-γ production of T cells

Background: Recent studies provide evidence that venom immunotherapy (VIT) alters the pattern of cytokine production by inducing an allergen-specific T-cell shift in cytokine expression from T-H2 (IL-4, IL-5) to T-H1 (IFN-gamma) cytokines and also inducing the production of IL-10. Objective: This study was carried out to analyze whether these changes in cytokine production of T cells already observed 1 week after the initiation of VIT in subjects with wasp venom allergy also influence the reactivity of effector cells, such as mast cells and basophils. Methods: All subjects included in this study had a history of severe systemic allergic reactions to wasp stings and positive skin test responses with venom and venom-specific IgE in the sera. Peripheral blood leukocytes were isolated before and after the initiation of VIT (rush therapy reaching a maintenance dose of 100 mu g venom injected subcutaneously within 1 week) and preincubated with or without addition of IL-10, IFN-gamma, IL-10 + IFN-gamma, anti-IL-10, or anti-IFN-gamma. After stimulation with wasp venom, histamine and sulfidoleukotriene release were assessed by ELISA and compared with spontaneous release and total histamine content. Results: After the induction of VIT, venom-induced absolute and relative histamine and sulfidoleukotriene release were reduced. This was at least partially due to the induction of IFN-gamma and IL-10 production, because (1) neutralization of IL-10 and IFN-gamma by mAbs partially restored the release after the initiation of VIT and (2) the addition of exogenous IFN-gamma and IL-10 caused a statistically significant diminution of the venom-induced histamine and sulfidoleukotriene release before VIT, Depletion of CD2(+) T cells also restored the releasability after VIT. Conclusion: These data indicate that T cells (producing IL-10 and IFN-gamma after VIT) play a key role for the inhibition of histamine and sulfidoleukotriene release of effector cells.