Nickel-induced activation of T cells in individuals with negative patch test to nickel sulphate

Contact hypersensitivity to nickel is the most common form of allergic contact dermatitis. To gain insight into the induction of this frequent disease, T cell reactivity towards nickel was investigated in "nonallergic" individuals defined as those with no skin manifestations and a negative patch test towards NiSO4. Surprisingly, we found that nickel induced proliferation of peripheral blood mononuclear cells (PBMC) from 16 of 18 adult individuals tested. This activation was specific, and no stimulation of PBMC was observed using control stimulants at equimolar concentrations. Furthermore, the NiSO4-induced activation required the presence of professional antigen-presenting cells. To describe the functional capacity of the nickel-inducible T cells, cytokine release was investigated in both nickel-allergic and nonallergic individuals. The T cells from both groups released interferon-gamma but no interleukin-4 upon stimulation with nickel, suggesting that the functional capacities of these cell populations were similar in nickel-allergic and nonallergic individuals. Thus, at this level, no qualitative differences could be demonstrated between T cells obtained from nickel-allergic and nonallergic individuals.