In vitro lymphocyte transformation to nickel: a study of nickel-sensitive patients before and after epicutaneous and oral challenge with nickel.

An in vitro lymphocyte transformation test (LTT) was performed in 8 patients with nickel contact dermatitis and in 4 control persons. The mitogenic response was of the same magnitude before patch testing, after patch testing and after oral challenge with nickel. When purified protein derivative (PPD) was used as the antigen, there was no difference between the LTT response of patients and controls before and after patch testing. After oral challenge with nickel, however, the patients' responses to PPD were significantly increased when compared with the responses after patch testing. The responses of the controls were unchanged. The LTT levels of the patients were approximately the same before and after patch testing, but were markedly increased after oral challenge.