Georg Kraal , Matthijs Breel , Marga Janse

Langerhans' cells (LC) l, veiled cells (VC), interdigitating cells (IDC), and dendritic cells (DC) form a group of non]ymphoid dendritic cells (NLDC) postulated to act primarily as antigen-presenting or accessory cells, in particular as inducers of T-dependent responses (1-5). The cells originate from bone marrow (3, 6, 7), but although it has been suggested that they belong to the mononuclear phagocyte system (8, 9), a direct relationship with monocyte] macrophage populations has not yet been proven. In contrast to typical macrophages, these DC show little phagocytic activity (10-12), whereas high levels of Ia antigens are constitutively expressed (13-16). LC are described as the primary immunocompetent cell in the skin, playing a role in the presentation of antigen to T cells and the induction of contact sensitivity (2, 4, 17). They can migrate from the skin into the afferent lymph (18, 19) as VC, characterized by their long, actively moving processes (19, 20). During their travel via the afferent lymph, VC can carry antigen, which may be presented to lymphocytes in the draining lymph node (21). Based on morphological criteria and localization patterns after cell transfer, it has been hypothesized that the IDC of the T cell-dependent area in lymph nodes are derived from immigrating VC (22, 23). An accessory role of the IDC in the immune response is assumed in studies with in vitro isolated DC. The in vitro isolated DC was first described by Steinman (3, 24) and although it has been suggested that IDC represent the DC (25, 26), it cannot be excluded that the in vitro DC belong to a functionally different subpopulation. The development of specific markers will give us more insight into the functions and relationships of these populations of nonlymphoid dendritic cells. In this study we describe an mAb that reacts with mouse LC, VC, and IDC.