Abstract
Nickel (Ni) is one of the most common causes of allergic contact dermatitis (ACD) and the number one allergen in the frequency of positive patch test reactions. The cellular basis of ACD is the lack of specialized T cells with regulatory function allowing for the expansion of Ni
specific cytotoxic CD8+ T cells. However, Ni also exerts a number of not yet fully understood activities on cells belonging to the immune system. To this regard, an immunosuppressive activity of Ni on natural killer (NK) cells has been repeatedly suggested both in animal models and humans. Here we demonstrate that NK activity of Ni
intolerant patients was significantly lower than observed in controls. Moreover, the addition of Ni
sulphate to cultures of peripheral blood lymphocytes (PBL) obtained by Ni
allergic patients, further depressed the NK cell activity. Finally, according to the key role exerted by NK cells in containing viral infections, we found an increased frequency of Herpesvirus 1 (HSV-1) recurrence among patients with Ni
allergy. In conclusion, our results indicate that Ni
allergic patients may present reduced NK cell response, this resulting in turn in increased susceptibility to viral infections. Patch testing should be considered in individuals affected by unexplained recurrences of HSV-1 infection.