Transcription factors are key molecules in the regulation of intracellular signalling processes. They are responsible for an integrated cellular response to multiple signals and exert their activity by binding to promoter sites of genes thereby enabling their transcription.
GATA-binding factor 3 (GATA-3) has been found to be strongly up-regulated in Th2 cells and it is well accepted that GATA-3 represents the central regulatory molecule in the differentiation and activation of Th2 cells (see chart below).
Source: Murphy and Reiner, Nat. Rev. Immunol. (2002)
It directly promotes the expression of the Th2 cytokines IL-4, IL-5, and IL-13 and suppresses the expression of counter-acting Th1 cytokines at the same time. Thus, GATA-3 is necessary and sufficient for Th2 cytokine expression in CD4-positive T cells. Very recently, it has been demonstrated that GATA-3 is also expressed in mast cells and eosinophils, i.e. effector cells of allergic immune responses.
In contrast, Tbet is the characteristic transcription factor of Th1 cells. It is expressed after appropriate stimulation of these cells and is responsible for the induction of Th1 cytokines, mainly of interferon-γ. In parallel, Tbet suppresses Th2-cytokine expression. Thus, Tbet is indispensable for the induction of Th1 cell activities.