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Allergic contact dermatitis to nickel: modified in vitro test protocols for better detection of allergen‐specific response

To date, no in vitro test is suitable for routine diagnosis of contact allergy. The aim of our study was to establish improved in vitro test protocol for the detection of antigen‐specific responses of lymphocytes from patients with allergic contact dermatitis to nickel (Ni‐ACD). Blood leucocytes from 14 Ni‐ACD patients and 14 controls were cultured in the presence of ‘cytokine cocktails’ skewing lymphocytes towards ‘type 1’ [interferon‐γ (IFN‐γ)‐secreting] or ‘type 2’ [interleukin (IL)‐5 and IL‐13‐secreting] phenotypes. The cocktails consisted of IL‐7 and, respectively, either IL‐12 or IL‐4. Cell responses to nickel were measured with enzyme‐linked immunospot assay (ELISpot), enzyme‐linked immunosorbent assay (ELISA), and lymphocyte proliferation test (LPT). Significant differences between patients with Ni‐ACD and controls were found for the ‘type 2’ cytokines IL‐13 and IL‐5, with further increase of allergen‐specific responses occurring when cultures were supplemented with IL‐7 and IL‐4. No significant differences were found for IFN‐γ. The best correlate to clinical diagnosis was LPT with ‘type 2’ skewing (r= 0.739, P < 0.001), followed by IL‐13 ELISpot with ‘type 2’ skewing (r= 0.654, P < 0.001). The non‐radioactive method that correlated best with LPT was IL‐2 ELISpot (r= 0.809, P < 0.001). Overall, we conclude that combining ELISpot assay with proposed modifications of culture conditions improves detection of specific lymphocyte responses in contact allergy to nickel.