An immunohistochemical study was carried out on the kinetics of Langerhans cells (LCs) at various pathological stages of "Kasen". Skin lesions of "Kasen" that were collected by biopsy from May to October were classified histopathologically into three stages: initial (Group I, 31 cases), developing (Group II, 50 cases) and regressing (Group III, 13 cases). LCs showed a positive reaction with antiequine thymocytes (EqT6) monoclonal antibody (MoAb) and anti-major histocompatibility complex (MHC)

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... ass II MoAb by immunohistochemical staining. The anti-EqT6 MoAb was intensely positive along the cytoplasmic process. The number of LCs per unit area increased markedly with the passage of time from the initial to the developing stage of the disease, particularly in the epidermo-dermal junction (EDJ). However, the number of LCs tended to decrease in the epidermal layer. In conclusion, the LCs moving into the epidermal layer moved into the EDJ and dermis during the time course of lesion development, and the changes occurring in LCs possibly influenced the progression of the skin lesions of "Kasen".-KEY WORDS: , , , , .