Abstract
The interactions between lymphocytes, Langerhals cells and keratinocytes, are described by electron microscopy in cutaneous lesions of malignant epidermotropic lymphomas (mycosis fungoides and Sézary's syndrome). Various contacts are observed between the different cells. During the degenerating process of keratinocytes, Langerhans cells disappear and histiocytic cells are bound to necrosing epidermal cells. The immunological process of Pautrier microabscess formation is discussed by comparison with ultrastructural aspects of cutaneous lecions of G.V.H. reaction in man.