PATIENTS WITH ALLERGIC CONTACT-DERMATITIS TO NICKEL AND NONALLERGIC INDIVIDUALS DISPLAY DIFFERENT NICKEL-SPECIFIC T-CELL RESPONSES - EVIDENCE FOR THE PRESENCE OF EFFECTOR CD8(-CELLS() AND REGULATORY CD4(+) T)

To investigate the mechanisms underlying the expression of allergic co ntact dermatitis, we compared the characteristics of nickel (Ni)-speci fic T cell responses in 10 patients with allergic contact dermatitis t o Ni and in 10 healthy, nonallergic individuals. CD4(+) T cells purifi ed from peripheral blood of both allergic and nonallergic subjects pro liferated similarly to NiSO4 in vitro, with the responses mostly restr icted 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 cel ls 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 inte rferon-gamma and higher interleukin-10 production compared with T cell clones from allergic patients. The T cell skin-homing receptor, cutan eous lymphocyte-associated antigen, was expressed on the large majorit y of specific CD4(+) clones from both the groups. Finally, Ni-specific CD8(+) clones prepared from patients also expressed the cutaneous lym phocyte-associated antigen receptor, and released high interferon-gamm a and no interleukin-4. In aggregate, the results suggest that the pre sence of specific CD8(+) T cells and a distinct pattern of cytokine re lease (e.g., an augmented production of interleukin-10) by CD4(+) T ce lls can be important elements in determining whether a hapten induces allergy or a silent immune response.