The pro- and anti-inflammatory properties of human antigen-presenting cells expressing the high affinity receptor for IgE (FcεRI)

Almost 20 years after the first description of IgE on the surface of epidermal Langerhans cells (LC) and the subsequent characterization of the trimeric FcεRI on human antigen-presenting cells (APC), we have gained profound insights into the receptor responsible for this binding. FcεRI may act as a pro-inflammatory structure on some APC such as inflammatory dendritic epidermal cells (IDEC) in the skin of patients with atopic dermatitis while it can also be an important instrument in mechanisms leading to tolerance on other APC such as LC of the oral mucosa. By virtue of FcεRI, APC can initiate inflammation by secretion of a wide spectrum of pro-inflammatory cytokines and chemokines. FcεRI+DC can induce either Th2 or Th1 profile in T-cells. In contrast, the production of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO) as well as IL-10 and TGFß may contribute to the tolerogenic properties of DC.