Epidermal Langerhans cells--changing views on their function in vivo.

New experimental models and methods have rendered the field of Langerhans cells very lively. An interesting and productive scientific debate as to the functions of Langerhans cells in vivo is currently going on. We have not yet reached the point where the "pros" would weigh out the "cons", or vice versa. There is good evidence for a lack of Langerhans cell function and for down-regulatory Langerhans cell function in some models. On the other hand, there is also evidence for an active immunogenic and tolerogenic role of Langerhans cells. These recent developments will be discussed.