Unexpected functions of Fc epsilon RI on antigen-presenting cells

In contrast to mast cells and basophils, the high affinity IgE receptor (Fc epsilon RI) on antigen-presenting cells (APC) shows structural and functio nal differences. It consists only of a minimal structure of one alpha- and two gamma -chains and enables APC to efficiently take up and present antige n in IgE-mediated delayed-type hypersensitivity reactions that are thought to play a pivotal role in atopic diseases. However, recent studies of Fc ep silon RI signal transduction and function on APC suggest additional mechani sms by which Fc epsilon RI engagement on APC could affect inflammatory reac tions, FceRI ligation is able to induce major signaling events like protein tyrosine kinase activation including p72(syk) leading to PLC-yl phosphoryl ation and consecutive calcium influx. Late signaling events like the activa tion of transcription factors such as NF-KB provide a link to the release o f proinflammatory cytokines and chemokines, Th-polarizing factors such as I L-12 and the induction of antiapoptotic factors, Fc epsilon RI-mediated IL- 10 production in monocytes could also influence their differentiation. Sinc e there are hints that in vivo a functional Fc epsilon RI signaling pathway only exists in individuals from an atopic background, we suggest that thes e unexpected mechanisms may have an effect on inflammatory reactions in ato pic diseases. Copyright (C) 2001 S. Karger AG,Basel.