CD4+ T cells producing interleukin (IL)-17, IL-22 and interferon-γ are major effector T cells in nickel allergy

Background. It has been suggested that interleukin (IL)-17 and IL-22 play important roles in the elicitation of human allergic contact dermatitis; however, the frequencies of T cell subtypes producing IL-17 and IL-22 in human allergic contact dermatitis are unknown. Objectives. To determine the frequencies of CD4(+), CD8(+) and gamma delta T cells producing IL-17, IL-22 and interferon (IFN)-gamma in the blood and skin from nickel-allergic patients. Patients/materials/methods. Blood samples were collected from 14 patients and 17 controls, and analysed by flow cytometry. Biopsies were taken from 5 patients and 6 controls, and analysed by immunohistochemistry and flow cytometry of skin lymphocytes. Results. We found an increased frequency of gamma delta T cells in the blood, but no differences in the distribution of cytokine-producing CLA(+) T cell subtypes in nickel-allergic patients as compared with controls. In nickel-allergic patients, there was massive cellular infiltration dominated by CD4(+) T cells producing IL-17, IL-22 and IFN-gamma in nickel-challenged skin but not in vehicle-challenged skin. Conclusion. CD4(+) T cells producing IL-17, IL-22 and IFN-gamma are important effector cells in the eczematous reactions of nickel-induced allergic contact dermatitis in humans.