THROMBOMODULIN EXPRESSION ON DERMAL CELLS IN NORMAL AND PSORIATIC SKIN

The various subsets of dermal cells with a dendritic appearance can be identified by phenotypic differences in cell markers. We report on th e morphology and tissue distribution of dermal cells detected with a m onoclonal antibody against thrombomodulin in histological sections of normal arm and scalp skin and psoriatic skin. Double staining with ant ibodies to factor XIIIa, CD34 and CD68 was also employed in scalp biop sies to elucidate the relationship between thrombomodulin(+) dermal ce lls and dermal dendrocytes and macrophages described by others. Thromb omodulin(+) dermal cells in normal arm skin had little cytoplasm with fine branched dendrites and tended to be localized just beneath the ep idermis, In scalp skin these cells had longer, more numerous dendrites and were distributed in the papillae and perivascular adventitial der mis primarily in the upper and central reticular dermis, In psoriatic skin, thrombomodulin(+) dermal cells had an increased cytoplasmic volu me with stout, less branched dendrites and appeared in the papillae an d among inflammatory cells. Dermal cells detectable by thrombomodulin expression were factor XIIIa(-), CD34(-) and CD68(-), and seemed to re present a distinct subset of dermal cells which may function in tissue repair, However, thrombomodulin(+) dermal cells and factor XIIIa(+) d endrocytes were frequently seen close together and could act cooperati vely to regulate extravascular thrombin homeostasis in both normal and pathological dermal environments.