title: Langerhans cells and vasculitis.
abstract: Langerhans cells are members of the dendritic cell system, which reside in the skin. These cells have many immunohistochemical and ultrastructural markers (for example, they are CD1a+ and possess Birbeck granules), which consent to identify them in an infiltrate. Langerhans cells have the specific role to present the antigens to T lymphocytes and to induce the cell-mediated immune reaction. Cutaneous necrotizing vasculitis (CNV) can be divided in two major forms: a leukocytoclastic type and a lymphocytic type. The pathogenesis of the first one is presumably immune complex-mediated, while for the second one a cell-mediated immunity has been proposed. Our group investigated on the cell infiltrate of some cases of CNV, both leukocytoclastic and lymphocytic type; and for leukocytoclastic CNV two phases were studied: an early one (at the onset of the lesion) and a later one (more than 24 hours). Special attention was paid to the presence of dendritic cells in the infiltrate and to their relationship to lymphocytes, if present. By immunohistochemistry and electron microscopy we could find many Langerhans cells and T lymphocytes in lymphocytic and in the late phase of leukocytoclastic CNV. The observed pattern of the cell infiltrate suggests that a cell mediated immune response play a major role in the pathogenesis of lymphocytic vasculitis and that dendritic cells and lymphocytes contribute to self-perpetuate leukocytoclastic vasculitis, which cannot be anymore considered as simply due to infiltration of neutrophils.
authors.affiliation: Department of Human Anatomy and Istology, University of Florence, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Romagnoli
authors.forename: I
authors.initials: I
authors.lastname: Ghersetich
authors.forename: T
authors.initials: T
authors.lastname: Lotti
mesh_terms: D000818:Animals; D006801:Humans; D007801:Langerhans Cells / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure*; D009336:Necrosis; D017445:Skin Diseases, Vascular / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D014657:Vasculitis / Q000276:immunology / Q000378:metabolism / Q000473:pathology*