Immunohistochemical discrimination of plasmacytoid dendritic cells from myeloid dendritic cells in human pathological tissues.

Until now, no method has been available to discriminate mature plasmacytoid DC (pDC) from myeloid DC (mDC) immunohistochemically. In this study, we report that these DC-subsets can be distinguished in routine pathological sections. Immature and mature monocyte-derived DCs (MoDCs) were S100 calcium binding protein B (S100B)+, while pDCs generated from pDC-precursors were S100B-. In contrast, both mature MoDC and pDC were fascin+. Epidermal Langerhans cells (LCs) were S100B+/fascin-. Although the majority of DCs were S100B+/fascin+ in the dermis with nonspecific inflammation, dermal DCs were mostly S100B-/fascin+ in psoriasis vulgaris, in which type I interferon secreted by pDC-precursors is thought to play a major role. S100B+/fascin+ DCs were accumulated in the superficial lymph node (LN), while they were scarce in the deep LN. In the superficial LN with dermatopathic lymphadenitis, a large number of S100B+/fascin+ DCs were accumulated in the T-zones, where numerous LC-derived DCs are accumulated. In contrast, almost all DCs were S100B-/fascin+ in the superficial LN with Kikuchi's lymphadenitis, in which numerous pDC-precursors are known to be present. In contrast to the superficial LN, the deep LN contained numerous S100B-/fascin+ DCs and a few S100B+ DCs. Thus, the distributions of S100B+ DC or S100B-/fascin+ DC correspond to the putative distribution of mDC or mature pDC, respectively.