Langerhans cells from human oral epithelium are more effective at stimulating allogeneic T cells in vitro than Langerhans cells from skin

This report is focused on the functional capacity of Langerhans cells (LC) in the epithelium of skin and oral mucosa, which both meet different antigenic challenges. The capacity of LC from human oral and skin epithelium to provide co-stimulatory signals to T cells in vitro was compared. LC in a crude suspension of oral epithelial cells had a significantly enhanced T cell co-stimulatory capacity compared to skin epithelial cells. This applied both to cultures with concanavalin A (con-A)-stimulated syngeneic T cells and to a mixed epithelial cell lymphocyte reaction involving allogeneic T cells. The co-stimulatory capacity of oral and skin epithelial cells was reduced by >70% if monoclonal antibodies against HLA-DR, -DP and -DQ were added to the cultures with allogeneic T cells, indicating the involvement of HLA class II expressing LC. Immunohistochemistry revealed that 6% of the epithelial cells were CD1a + LC in sections from both oral and skin epithelium. Interleukin (IL)-8 production was higher in cultures of oral epithelial cells and con-A stimulated T cells than in corresponding cultures with skin epithelial cells as accessory cells. The results suggest that LC in human oral epithelium are more efficient at stimulating T cells than those of skin.