Cytokine patterns in vitro, in particular IL-5/IL-8 ratio, to detect patients with nickel contact allergy

Background: Patch test (PT) is the gold standard to reveal nickel (Ni) allergy. In vitro tests are under discussion. We aimed to establish a cytokine based in vitro assay to detect Ni sensitization. Methods: From 15 patients with positive (13f, 42–78 years) and 15 with negative PT to Ni (controls, 3f, 31–82 years) within a consecutive patient series, peripheral blood mononuclear cells (PBMC) were obtained. Six-day stimulation with three concentrations of NiSO₄ was performed. Proliferative response (uptake of tritiated thymidine) and production of the cytokines IL-1β, IL-4, IL-5, IL-6, IL-8, IL-10, IL-17A, TNF-α, IFN-γ (cytometric bead array) were assessed. Results: Twelve of fifteen Ni PT-positive patients also had positive LTT, and all control patients were PT and LTT negative. The mean SI differed between Ni allergics and controls (P < 0.01). Upon Ni stimulation, PBMC of the allergic patients showed (i) enhanced IL-5 response (P < 0.0001) and (ii) reduced IL-8 production (P < 0.01). The IL-5/IL-8-ratio best distinguished allergics from non-allergics in all three Ni concentrations with a sensitivity and specificity of 93%. Conclusion: Assessment of the ratio of Ni-induced IL-5 and reduced IL-8 production in vitro is a helpful tool for a better characterization of Ni-allergic patients.