Initiation and maintenance of Th2 cell identity.

T helper type 2 (Th2) cells produce IL-4, IL-5, and IL-13 and play an important role in humoral immunity and allergic reactions. During Th2 cell differentiation, naïve CD4 T cells acquire 'Th2 cell identity', that is, the capability to produce selectively a large amount of Th2 cytokines. Th2 cell identity is maintained in memory Th2 cells. Significant advances in understanding of the molecular requirement for these processes have been made. The expression of GATA3, a master transcription factor for Th2 cell differentiation, is uniquely regulated by several distinct mechanisms. Molecular analyses of memory Th2 cells revealed that cell survival and the maintenance of Th2 cell function are epigenetically regulated by various nuclear factors, including Polycomb and Trithorax molecules.