ORAL DESENSITIZATION IN NICKEL ALLERGY INDUCES A DECREASE IN NICKEL-SPECIFIC T-CELLS

Nickel (Ni) is the most frequent cause of allergic contact dermatitis, mainly in female patients. In animals, oral tolerance to Ni sensitiza tion can be obtained by feeding with Ni sulfate (NiSO4). The aim of th e present study was to compare the specific proliferative responses an d frequencies of Ni-responding T cells from peripheral blood of patien ts before and after a protocol of Ni ingestion. Ten patients with chro nic disseminated eczema and patch test-proved contact allergy to Ni ga ve informed consent for the study. All were non-pregnant female patien ts between the ages of 21 and 40 years (mean 35 years). They ingested 22.4 mg NiSO4 (5 mg Ni) once a week for 8 weeks. All patients experien ced an exacerbation of pruritus 12 to 24 hours after ingesting the fir st capsules, resolving within 24 hours. Two patients had a major flare -up of their eczema. Eight patients completed the whole study, and pre sented a progressive improvement of their cutaneous lesions. In these patients, the sums of individual epicutaneous test scores were decreas ed after 8 weeks (p<0.02). Peripheral blood lymphocytes (PBL) were iso lated and stored before and after Ni ingestion. Proliferation assays w ere performed with 5 x 10(-5) mol/I NiSO4. Stimulation indexes were de creased after 8 weeks when compared to preingestion PBL (p<0.02). A li miting dilution assay was developed to quantify Ni-specific T cells fr om peripheral blood. The frequencies of responding T-cells were decrea sed after 8 weeks (1/49 061 to 1/2 517 920), when compared to preinges tion PBL (1/14 547 to 1/128 682). Our results confirm that oral hypose nsitization may decrease the degree of contact hypersensitivity as mea sured by epicultaneous test and induce clinical improvement of cutaneo us lesions. In addition, oral nickel intake can decrease Ni-specific p roliferations and the numbers of Ni-responding T cells in peripheral b lood. These data open a new area of investigation of the treatment of Ni allergy.