Abstract
Characterization of the ability of interferons to induce immediate early genes led to the identification of the signal transducer and activators of transcription (STAT) signaling paradigm, where a single protein transduces signals directly from the receptor to the nucleus. Subsequent studies have determined that all cytokines transduce pivotal signals through at least one of the seven members of this STAT family. Notably, cytokines can be placed in functional subgroups based on the STATs they activate.