The pro- and anti-inflammatory potential of IL-12: the dual role of Th1 cells.
The differentiation of T-helper (Th) lymphocytes into various types of T-helper effector and memory cells with distinct functions depending on the type of concomitant signals they receive upon activation is a critical event determining the course of an immune reaction. Th1 cells characterized by the expression of IFN-gamma and the recently described Th17 cells promote inflammation and are critically involved in the induction and maintenance of autoimmunity, whereas the secretion of IL-4 is a hallmark of Th2 cells mediating protection from parasites and allergy. Original stimulation in the presence of IL-12 results in the imprinting of Th1 memory cells for the expression of IFN-gamma by expression of the transcription factor T-bet and epigenetic modification of the ifngamma gene. It has been demonstrated that Th1 cells are potent inducers of inflammation. However, in the chronic phase of such inflammation, the regulatory potential of IL-12 and Th1 cells themselves may play an important role in limiting immunopathology.
Chang
Hyun-Dong
HD
German Rheumatism Research Center, Charitéplatz 1, 10117 Berlin, Germany. chang@drfz.de
Radbruch
Andreas
A