Analysis of effector and regulatory immune reactivity to nickel

Summary 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.