The Interleukin-4 Enhancer CNS-2 Is Regulated by Notch Signals and Controls Initial Expression in NKT Cells and Memory-Type CD4 T Cells

Abstract

Epigenetic changes in chromatin structure at the T helper (Th2) locus correlate with interukin-4 (IL-4) and IL-13 expression during Th2 differentiation. By using a transgenic green fluorescence protein (GFP) reporter system, we show that conserved noncoding sequence-2 (CNS-2), located downstream of the Il4 locus, is a constitutively active enhancer in NKT cells as well as in a subset of CD44(hi) memory phenotype CD4+ T cells. CNS-2 enhancer activity and initial IL-4 expression in CD44(hi) CD4+ T cells were abolished in mice with a CD4-specific deletion of the transcriptional mediator of Notch signaling, Rbp-j. Depletion of CNS-2 active CD4+ T cells markedly decreased Th2 differentiation from naive CD4 T cells and antigen-specific IgE production after in vivo priming. These findings indicate that Notch-regulated CNS-2 enhancer controls initial IL-4 expression in NKT and memory phenotype CD4+ T cells and that CNS-2 active CD44(hi) memory phenotype T cells are important in facilitating Th2 differentiation of naive CD4+ T cells in allergic responses.

Regulation of innate and adaptive immunity by Notch

“…Regulation of T H 2 cell differentiation in vivo by Notch was documented in several experimental models 81,82 .…”

“…Several RBPJ-binding sites were identified on the Il4 enhancer (conserved non-coding sequence 2 (CNS2); also known as HS5), suggesting a direct role of Notch in IL-4 transcription in T H 2 cells, NKT cells and possibly other IL-4-secreting cells 72,82 . As IL-4 is a master regulator of T H 2 cell differentiation, Notch signalling may thereby promote T H 2 cell differentiation by both cell-intrinsic and cell-extrinsic mechanisms.…”

CD1d-restricted iNKT cells, the ‘Swiss-Army knife’ of the immune system

“…Epigenetic changes in chromatin structures at the IL-4 and IFNγ loci are known to occur during iNKT cell development in the thymus [29]. It was reported that Notch signaling might control the activity of an enhancer located downstream of the IL-4 locus that is responsible for the initial IL-4 expression in iNKT cells [45]. Similarly, identification of regulatory regions that might control IFNγ gene expression by iNKT cells are starting to emerge [46].…”

How are TH1 and TH2 effector cells made?

“…Also, Notch directly activates transcription of the Il4 gene via conserved RBP-J binding sites in the HS5 enhancer (Fig. 2) [18,38]. The fact that IL4 is genetically downstream of Notch explains why exogenously added IL4, such as in traditional cytokine mediated skewing experiments, overcomes the requirement for Notch in T H 2-cell differentiation [30,39].…”

“…3), and together controlled expression of reporter transgenes in a T H 2-specific fashion [47,48]. Among these is the 3′ Notch responsive enhancer HS5 [18,38]. Additionally, seven hypersensitive sites exist more distally.…”