Analysis of effector and regulatory immune reactivity to nickel

Background: Diagnostic patch testing in allergic contact dermatitis faces the risk of boosting existing hypersensitivities or active sensitization. Risk-free and reliable in vitro assays using peripheral blood are, therefore, wanted. Objectives: Here, we studied new approaches for in vitro monitoring of nickel-specific effector ad regulatory cell functions in allergic patients and potentially tolerized individuals. Methods: Lymphocyte proliferation assays were carried out with the allergen and additional IL-12/ IL-7 or IL-4/IL-7 cytokine supplements. Release of IFN-γ and IL-5 were assessed as measures for type-1 and type-2 effector T cell function, respectively, and IL-10 and TGF-β₁ to monitor possible regulatory T cell function reflecting immunological tolerance. After optimization of in vitro cut-off values, potency of these parameters was evaluated as compared with conventional nickel patch testing. Results: One hundred and fifty six outpatients were included in this study, 74 of whom presenting with a positive history of nickel allergy. Nickel-sulphate patch test results showed positive reactions in 43 patients, of whom 40 had a positive history (test sensitivity 54%; specificity 96%; overall accuracy 76%). Proliferation tests without cytokine supplementation showed an accuracy of 68%, which was further improved by supplementing IL-4/IL-7 (82%). IFN-γ and IL-5 cytokine production, as revealed in IL-12/IL-7 and IL-4/IL-7 supplemented cultures, respectively, showed accuracies of 70% and 83%. As to the production of putatively immunoregulatory cytokines, IL-10 was most informative, with highest production rates in nickel-skin test negative individuals with long-lasting mucosal metal contact preceding skin piercing. Conclusions: These results indicate that measuring both T cell proliferation and cytokine secretion profiles, in particular IL-5 release using IL-4/IL-7 supplemented medium, offers a promising improvement of the in vitro diagnostic options in monitoring nickel contact sensitization. Since oral nickel contact has been shown earlier to induce active tolerization, nickel-induced in vitro IL-10 production may help identify nickel-tolerized individuals.