title: Immunopathology of pityriasis lichenoides acuta.
abstract: Eleven biopsy specimens (five papules and six dusky or crusted lesions) from four patients with pityriasis lichenoides et varioliformis acuta ( PLEVA ) were studied by direct immunofluorescence and immunoperoxidase technics. Slight vascular deposits of IgM and C3 were present in most lesions. Slight perivascular deposits of fibrin were observed in early lesions; more extensive perivascular and interstitial deposits of fibrin were detected in advanced lesions. Most of the infiltrating cells were T lymphocytes; cells with cytotoxic/suppressor phenotype (T8-positive) were generally more numerous than cells with helper/inducer phenotype (Leu-3a-positive, T4-positive). A marked increase in epidermal T8-positive cells over epidermal Leu-3a/T4-positive cells was found in late lesions. Moreover, a reduction of the ratio of circulating T4-positive to T8-positive cells was observed in most cases. The number of epidermal T6-positive (Langerhans/indeterminate) cells was decreased in the lower as compared with the upper stratum spinosum. About 5% of perivascular infiltrating cells were T6-positive. These results suggest that cell-mediated immune mechanisms are probably important in the pathogenesis of PLEVA .
mesh_terms: D000328:Adult; D000911:Antibodies, Monoclonal / Q000276:immunology; D003176:Complement C3 / Q000032:analysis; D005260:Female; D005337:Fibrin / Q000032:analysis; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007111:Immunity, Cellular; D007124:Immunoenzyme Techniques; D007136:Immunoglobulins / Q000032:analysis; D007801:Langerhans Cells / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010915:Pityriasis / Q000276:immunology / Q000473:pathology*; D013601:T-Lymphocytes / Q000145:classification / Q000473:pathology*
chemical_list: D000911:Antibodies, Monoclonal; D003176:Complement C3; D007136:Immunoglobulins; D005337:Fibrin