Allergic Contact Dermatitis: Novel Immunohistologic Features

Leu-8 is a novel antigen expressed by the majority of mature T cells and certain other cells. Recent studies of the allogeneic mixed leukocyte reaction indicate that both Leu- 8+ and Leu-8- subsets of Leu-3+ T cells have important functions in cell-mediated immunity in vitro. In order to determine whether Leu-3+8+ and/or Leu-3+8- T cells are present in cell-mediated immune reactions in vivo, we studied the immunohistology of allergic contact dermatitis in 8 biopsies from 8 patients with positive patch tests and 3 biopsies from 2 patients with Rhus dermatitis. Both Leu-3+8+ and Leu-3+8- T cells were present in each biopsy. Only 1 case had a definite minority of the Leu-3+8+ subset. These results suggest that, analogous to in vitro systems, both Leu-8+ and Leu-8- subsets of Leu-3+ T cells are involved in cell-mediated immunity in vivo. HLA-DR+ keratinocytes were present in only 3 of 11 biopsies at days 3-7. No HLA-DQ+ keratinocytes were identified. We also confirmed prior findings that Leu-3+ cells are the predominant T-cell population, Langerhans cells are increased, and B cells and NK cells are rare. Furthermore, Tac and Ki-67 expression by T cells and Leu-3 expression by Langerhans cells tended to increase over time.