Fas/Fas ligand-mediated elimination of antigen-bearing Langerhans cells in draining lymph nodes.

Epidermal Langerhans cells (LC) are potent antigen-presenting cells (APC) that play a crucial part in initiating cutaneous immune responses. Although functional roles of LC as APC in the draining lymph node have been well investigated, little is known about the fate of LC after the antigen presentation to T cells. In this report, we demonstrate that antigen-bearing LC that migrated into the draining lymph nodes and were identified as fluorescent cells after skin painting with fluorescein isothiocyanate also expressed the Fas antigen. Clearance of the antigen-bearing LC was significantly delayed and the ratio of dead cells was reduced in Fas-deficient lpr and Fas ligand (FasL)-deficient gld mice at 2 days after skin painting, suggesting the involvement of a Fas/FasL-mediated pathway in the elimination of antigen-bearing LC in draining lymph nodes. These results suggest that a substantial population of LC after antigen presentation may undergo Fas/FasL-mediated apoptosis and that the elimination of active APC may be important for preventing excess immune responses.