EPITHELIUM-LINING MACROPHAGES IN PSORIASIS

Epithelium-lining macrophages are spindle-shaped cells which line the epidermis and hair follicles. We studied the distribution and phenotyp e of this hitherto neglected member of the dermal monocyte/ macrophage system in 25 lesional psoriatic, and five normal skin biopsies. Epith elium-lining macrophages were inconspicuous in normal skin, whereas th eir number was increased in almost two-thirds of psoriatic cases; in n ine out of 25 lesional skin biopsies, these flattened cells formed an almost continuous single-cell row at the dermo-epidermal junction. Imm unophenotyping revealed that these cells expressed the leucocyte commo n antigen CD45, and the macrophage markers CD14, CD36 and CD4, but not CD11b. Epithelium-lining macrophages strongly expressed HLA-DR-antige ns and CD11a, but lacked the Langerhans cell marker CD1, and CD34. The dermal dendrocyte marker factor XIIIa was expressed in only a minorit y of these cells. It is concluded that epithelium-lining macrophages r epresent a separate subset of dermal monocytes/macrophages with a dist inct tissue localizaton and immunophenotype. Their restricted distribu tion and close association with the epidermis may suggest a role in th e regulation of epidermal growth. Alternatively, the expression of sev eral immune-associated molecules may indicate that epithelium-lining m acrophages are involved in the antigen-dependent or -independent activ ation of T cells.