Jak-Stat signal transduction pathway through the eyes of cytokine class II receptor complexes

Cells of the immune system communicate with each other to initiate, establish and maintain immune responses. The communication occurs through cell-to-cell contact or through a variety of intercellular mediators that include cytokines, chemokines, growth factors and hormones. In the case of cytokines, the signal is transmitted from the outside to the inside of a cell through cell surface receptors specific for each cytokine. At this step the signal is also decoded and amplified: ligand binding causes recruitment and/or activation of numerous cytoplasmic proteins. One cytokine can activate a number of signal transduction pathways leading to regulation of a wide array of biological activities. One of these pathways, the Jak-Stat pathway, is briefly reviewed here with respect to the class II cytokine receptors. Signal transduction through receptors for interferons Type I (IFN-α, IFN-β, IFN-ω) and Type II (IFN-γ), and interleukin 10 (IL-10) is described in detail. In addition, a complex between tissue factor (TF) and coagulation factor VIIa, and two new receptors related to the class II cytokine receptor family are discussed.