Langerhans cell induced cytotoxic T-cell responses against normal human epidermal cell targets: in vitro studies.

We investigated the role of class II MHC (HLA-DR Ia-like) antigen-bearing Langerhans cells in the in vitro generation of human alloreactive cytotoxic T lymphocytes (CTL) directed against epidermal cells (EC). Normal EC in suspensions (from reconstructive surgery specimens) and anti-DR monoclonal antibody plus complement (C')-treated EC were used to stimulate peripheral blood (PB) T cells (T cells allogeneic or autologous to EC) in a classical 6-day human mixed skin cell-lymphocyte culture reaction (MSLR). CTL responses were then tested in 51Cr release assays against cultured EC (EC grown on collagen-coated plates in parallel to MSLR). CTL responses to EC were observed only after allogeneic MSLR and when targets and EC used in MSLR were from the same donor. They were comparable in magnitude to those seen in parallel studies using PBL from the same donor as the stimulating EC as target cells. They were abolished when EC used in MSLR were depleted in class II MHC Langerhans cells (preincubation of EC suspensions with anti-DR + C'). These data show: (a) alloreactive CTL to human normal EC may be generated in MSLR, as previously shown in animals; (b) the MSLR is an in vitro model of primary immunization against EC; (c) Langerhans cells are necessary for the generation of cell-mediated cytotoxicity reactions occurring against epidermal cells.