gamma/delta T lymphocytes in leukocytoclastic cutaneous necrotizing vasculitis: A clue to the infective etiology

Cutaneous necrotizing vasculitis (CNV) has been traditionally divided into leukocytoclastic and lymphomonocytic forms. We studied by immunohistochemistry the infiltrate of 9 cases of the leukocytoclastic form of CNV in two phases (early and late), 5 with a documented infective etiology and 4 with unknown etiology. The aim of the study was to evaluate:1. The immunophenotypical characteristics of the infiltrate; 2. The expression of some adhesion molecules receptors; 3. The presence of gamma/delta T cells and the expression of heat shock proteins (HSPs), Our results showed a poor infiltrate of CD4+, CD1a+ cells in the early phase of leukocytoclastic vasculitis, while the perivascular infiltrate was rich of these cells in the late phase. LFA-1 and ICAM-1 were strongly expressed in the late phase, gamma/delta T cells and the expression of HSP72 kD were significantly present only in leukocytoclastic CNV with documented infective etiology. These data seem to suggest the participation of a secondary cell-mediated immune response in the late phase of leukocytoclastic CNV. Moreover, the presence of gamma/delta T cells could be a possible clue to the infective etiology of CNV.