Peribronchiolar accumulation of dendritic cells and their close association with CD4(+) T cells in the murine lung hypersensitivity

In order to understand the interaction between dendritic cells (DCs) and he lper T (Th) cells in the region exposed to antigens during pulmonary delaye d-type hypersensitivity (DTH), which is considered to be mediated by Th1 ce lls, we immunohistochemically investigated their spatial relationship in th e cellular infiltrate. At 24 hours after intratracheal instillation of hapt en in sensitized mice, DCs were preferentially accumulated around the bronc hioles, whereas macrophages were more abundant around the accompanying arte ries. DCs often formed a cluster, in which they were interconnected with ea ch other by projections. Serial section analysis revealed that clustered DC s made a close apposition to Th cells but much less frequently to cytotoxic T cells and B cells. Immunoelectron microscopy demonstrated that lymphocyt es extravasated the capillaries in the peribronchiolar interstitium and mad e conjugation with DCs. In the interstitial tissue, DCs often adhered to th e fibroblasts, suggesting the supportive role of the latter cells in DC mig ration. Eosinophils were also frequent around the arteries, representing th e possible involvement of Th2 cytokines. By contrast, in a chronic type of airway inflammation induced by repeated challenges of aerosolized ovalbumin , DCs were densely and diffusely accumulated around the arteries in the sam e way as macrophages. The present study demonstrated a close association of DCs with Th cells around the bronchioles during pulmonary DTH, suggesting that local interaction between them in the lung may play important roles in the development of this disorder. (C) 2001 Wiley-Liss. Inc.