[Parapsoriasis en plaques. Characterization of the cellular infiltrate using monoclonal antibodies].

We report on a 65-year old woman suffering from parapsoriasis with large plaques. The cellular infiltrate was analysed by means of monoclonal antibodies and an immunoperoxidase technique. Our findings proved that the majority of the cellular infiltrate in the upper dermis is composed of helper-inducer T-cells (Leu 4+, Leu 3a+). A notable number of Leu-2a-reactive suppressor-cytotoxic T-cells associated with hydropic degeneration of the basal cell layer were found within the dermal infiltrate and the dermoepidermal interface. Large numbers of Leu-6-reactive dendritic Langerhans' cells were noted in the lower layers of the epidermis, in particular in areas where the epidermis showed focal exocytosis of lymphoid cells. Langerhans' cells, in contrast, were present in the upper portions of epidermis lacking exocytic T-cells. HLA-DR antigens were expressed on Langerhans' cells as well as on nearly all T-lymphocytes. Positive intercellular staining for HLA-DR antigens were only found in localized areas of the epidermis. Small numbers of both Leu-11B-reactive natural killer cells and cells expressing interleukin-2 receptors were seen within the basal cell layer and at the dermo-epidermal junction. Our findings suggest that a cell-mediated immune response which is directed against antigens expressed by keratinocytes may play an important role in the pathogenesis of parapsoriasis en plaques.