Transcriptional regulation in the immune system: all roads lead to AP-1.

The mechanisms regulating the development and function of the immune system are diverse and complicated. The signaling pathways and target genes that become activated upon cell-surface stimulation are currently being defined, and transcription factor activator protein 1 (AP-1) is proving to be an important regulator of nuclear gene expression in leukocytes. In vitro and in vivo studies have demonstrated that AP-1 expression is induced after a diverse range of stimuli and that AP-1 contributes to the regulation of a large number of genes. In this review we will examine the role of AP-1 during leukocyte activation and differentiation in the immune system.