CD68 POSITIVE EPIDERMAL DENDRITIC CELLS

In a pilot study designed to investigate immunopathologic events in th e 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 nov el intraepidermal CD68+ cell population. For that purpose lesional ski n of five patients with PF and, for comparison, of patients with anoth er acantholytic autoimmune discase, pemphigus vulgaris, were examined using a panel of monoclonal antibodies in a three-step immunoperoxidas e technique, in an immunofluorescence double-labeling technique, and b y 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 expr essed CD68, HLA-DR, and beta2-integrin antigens, the most pronounced e xpression being observed for CD11c and CD18. These epidermal CD68+ cel ls were of dendritic shape, were CD1a-, and lacked Birbeck granules (B G); however, a small portion of CD68+ cells was also CD1a+ and exhibit ed BG as revealed by immunoelectron microscopy. These findings demonst rate that in certain conditions, i.e., in pemphigus foliaceus but not in pemphigus vulgaris, there is a shift from CD1a+/CD68- epidermal Lan gerhans cells towards CDla-/CD68+ dendritic epidermal cells. The detec tion of a small number of CD1a+/CD68+/BG+ dendritic epidermal cells ma y identify these cells as a link between the CD1a+/CD68+/BG+ Langerhan s cells and the CD1a-/CD68+/BG-cell population and suggests that these cells represent a transitional form of myelomonocytic cells during th eir phenotypic and morphologic transformation into resident epidermal Langerhans cells.