IFN-gamma-production by antigen-presenting cells: mechanisms emerge

The suggestion that antigen-presenting cells (APCs) produce interferon gamm a (IFN-gamma) is controversial because it conflicts with the initial paradi gm in which the production of IFN-gamma was restricted to lymphoid cells. H owever, some answers to this skepticism have been provided by recent findin gs of high-level production and intracellular expression of IFN-gamma by in terleukin-12 (IL-12)-stimulated macrophages and dendritic cells. New data a re now emerging to explain the mechanism of production of IFN-gamma vby APC s. As in lymphoid cells, IL-12-induced IFN-gamma production in APCs require s signal transducer and activator of transcription 4 (STAT4), although the precise molecular events that govern the transcription of the gene encoding IFN-gamma are enigmatic still. Understanding these processes in lymphoid, and now nonlymphoid, cells remains an important challenge.