Lymphocyte subset changes in blood and gastrointestinal mucosa after oral nickel challenge in nickel‐sensitized women

This study investigates lymphocyte subsets in both the gastrointestinal mucosa and blood, in patients with nickel allergic contact dermatitis, after 10 mg oral nickel challenge (double‐blind, placebo‐controlled). 6 such patients with cutaneous symptoms induced only by skin contact with nickel (group A), 6 with a flare‐up of cutaneous symptoms after food nickel ingestion (group B) and 6 healthy controls (group C) were enrolled. Blood lymphocyte subsets (CD4, CD45RO, CD8) were analyzed before and after 4 and 24 h from the challenge (test 1, 2, and 3), and intestinal biopsies were performed 2 days later. Challenges were positive in group B and negative in group A and controls. Serum and urine nickel levels significantly increased after nickel ingestion, with no differences between the 3 groups. At test 3, a significant decrease of the all CDs studied was found in group B. Biopsies of this group showed higher levels of CD45RO+ cells in the lamina propria and in the epithelium and lower levels of epithelial CD8+ lymphocytes. This study confirms that ingested nickel may induce flare‐up of cutaneous reactions in some nickel‐allergic patients, independently of the degree of sensitization and the intake of metal. In these patients, oral nickel stimulates the immune system, inducing maturation of T lymphocytes from virgin into memory cells; these latter cells seem to accumulate in the intestinal mucosa. The immunoreaction also involves CD8+ cells, whose role is not yet clear.