DENDRITIC CELLS IN CUTANEOUS LUPUS-ERYTHEMATOSUS - A CLUE TO THE PATHOGENESIS OF LESIONS

In view of the critical role of dendritic eels in immune mediated skin diseases, we have investigated the membrane antigen patterns and ultr astructure of cutaneous dendritic cells in eight patients with chronic discoid lupus erythematosus and five with subacute cutaneous lupus er ythematosus. In the lesional epidermis, the expression of HLA-DR antig ens by epidermal dendritic cells was reduced, as compared with periles ional, clinically normal skin. In addition, only few CD1a+ dendritic c ells (Langerhans' cells), along with some CD11c+ and CD14+ cells (pres umable precursors of Langerhans' cells), were found in atrophic areas of lesional epidermis. In contrast, the number of Langerhans' cells in non-atrophic areas of lesional epidermis was similar to that in peril esional skin. On electronmicroscopy, epidermal Langerhans' cells appea red depleted of organelles and dendrites and contained tubuloreticular inclusions. In the lesional dermis, both CD1a+ and CD36+ dendritic ce lls were found, associated with CD4+ and CD8+ T-cells, respectively. M oreover, CD11c+ and CD14+ cells were found around capillaries in the p apillary dermis on electronmicroscopy. Indeterminate cells (dendritic cells with features of Langerhans' cell lineage, but apparently withou t Birbeck granules) and dendritic macrophages were found, associated w ith lymphocytes and mast cells. No cells with intermediate/transitiona l features between these two dendritic cell types were found. Converse ly, peculiar dendritic cells-with short and blunt dendrites and cytopl asm containing many nat, rough cisternae, moderately well developed Go lgi apparatus and no lysosomes-were found in the same location as the CD11c+ and CD14+ cells identified by light microscopy. These findings might be interpreted as follows: 1 the alterations in cytological diff erentiation and expression of functionally meaningful molecules by epi dermal Langerhans' cells in cutaneous lupus erythematosus lesions sugg est an impairment of their immunological efficiency; 2 in the lesional dermis of cutaneous lupus erythematosus, a CD4+ T-cell/CD1a+ dendriti c cell-based delayed-type immune response is possibly modulated by a s uppressor T-cell circuit in which CD36+ dendritic cells may act as acc essory cells; 3 CD11c+ and CD14+ cells with peculiar ultrastructure ar e possible precursors of both CD1a+ indeterminate cells and CD36+ derm al dendrocytes in the dermis.