Patients with allergic contact dermatitis to nickel and nonallergic individuals display different nickel-specific T cell responses. Evidence for the presence of effector CD8+ and regulatory CD4+ T cells

To investigate the mechanisms underlying the expression of allergic contact dermatitis, we compared the characteristics of nickel (Ni)-specific T cell responses in 10 patients with allergic contact dermatitis to Ni and in 10 healthy, nonallergic individuals. CD4⁺ T cells purified from peripheral blood of both allergic and nonallergic subjects proliferated similarly to NiSO₄ in vitro, with the responses mostly restricted to CD4⁺ CD45RO⁺ memory T cells. In contrast, Ni-specific CD8⁺ T cell responses were detected only in allergic patients. Limiting dilution assay confirmed a high frequency of Ni-specific CD4⁺ T cells in both individual categories, and of Ni- specific CD8⁺ T cells in allergic patients, but not in nonallergic persons. Ni-specific CD4⁺ T cell clones prepared from nonallergic subjects displayed lower interferon-γ and higher interleukin-10 production compared with T cell clones from allergic patients. The T cell skin-homing receptor, cutaneous lymphocyte-associated antigen, was expressed on the large majority of specific CD4⁺ clones from both the groups. Finally, Ni-specific CD8⁺ clones prepared from patients also expressed the cutaneous lymphocyte-associated antigen receptor, and released high interferon-γ and no interleukin-4. In aggregate, the results suggest that the presence of specific CD8⁺ T cells and a distinct pattern of cytokine release (e.g., an augmented production of interleukin-10) by CD4⁺ T cells can be important elements in determining whether a hapten induces allergy or a silent immune response.