CD68 POSITIVE EPIDERMAL DENDRITIC CELLS

In a pilot study designed to investigate immunopathologic events in the evolution of cutaneous lesions in pemphigus foliaceus, we found that in this condition the epidermis is replete with CD68+ dendritic cells. The present study was designed to investigate the nature of this novel intraepidermal CD68+ cell population. For that purpose lesional skin of five patients with PF and, for comparison, of patients with another acantholytic autoimmune discase, pemphigus vulgaris, were examined using a panel of monoclonal antibodies in a three-step immunoperoxidase technique, in an immunofluorescence double-labeling technique, and by immunoelectron microscopy. We found epidermal CD1a+ Langerhans cells significantly decreased in pemphigus foliaceus compared to pemphigus vulgaris, but pemphigus foliaceus and not pemphigus vulgaris epidermis harbored large amounts of bone marrow-derived (CD45+) cells that expressed CD68, HLA-DR, and beta2-integrin antigens, the most pronounced expression being observed for CD11c and CD18. These epidermal CD68+ cells were of dendritic shape, were CD1a-, and lacked Birbeck granules (BG); however, a small portion of CD68+ cells was also CD1a+ and exhibited BG as revealed by immunoelectron microscopy. These findings demonstrate that in certain conditions, i.e., in pemphigus foliaceus but not in pemphigus vulgaris, there is a shift from CD1a+/CD68- epidermal Langerhans cells towards CDla-/CD68+ dendritic epidermal cells. The detection of a small number of CD1a+/CD68+/BG+ dendritic epidermal cells may identify these cells as a link between the CD1a+/CD68+/BG+ Langerhans cells and the CD1a-/CD68+/BG-cell population and suggests that these cells represent a transitional form of myelomonocytic cells during their phenotypic and morphologic transformation into resident epidermal Langerhans cells.