Chromatin structure and DNA methylation of the IL-4 gene in human T(H)2 cells.

Human T(H)2 cell differentiation results in the selective demethylation of several specific CpG dinucleotides in the IL-4 and IL-13 genes, which are expressed in activated T(H)2, but not T(H)1, cells. This demethylation is accompanied by the appearance of six DNase I hypersensitive sites within 1.4 kb at the 5'-end of the IL-4 gene.

The controversial 30 nm chromatin fibre.

DNA is packed as chromatin on several levels in the eukaryotic nucleus. Dissection of chromatin with nucleases produces three stable substructures: the nucleosome core particle, the chromatosome and the 30 nm fibre. Whilst the first two allow transcription, the 30 nm fibre is taken to be the first level of transcriptionally dormant chromatin and it has an important functional role in cell differentiation and epigenetic regulation.

The sequentiallity of nucleosomes in the 30 nm chromatin fibre.

The folding of eukaryotic DNA into the 30 nm fibre comprises the first level of transcriptionally dormant chromatin. Understanding its structure and the processes of its folding and unfolding is a prerequisite for understanding the epigenetic regulation in cell differentiation. Although the shape of the fibre and its dimensions and mass per unit length have been described, the path of the internucleosomal linker DNA and the sequentiallity of the nucleosomes in the fibre are poorly understood.

Analysis of intergenic transcription in the human IL-4/IL-13 gene cluster.

During the differentiation of naïve CD4+ precursors to T helper 1 (Th1) or Th2 effector cells, several epigenetic changes occur in a lineage-specific manner at the IFN-gamma or IL-4/IL-13 loci. These changes result in alterations in the chromatin structure of these loci and, hence, lineage-restricted expression of the corresponding cytokines. Intergenic transcripts have recently been shown to regulate the expression of genes in the beta-globin locus; therefore, we have examined the Th2 cytokine gene cluster during human Th1/Th2 differentiation and in a transgenic mouse line containing the human IL-4/IL-13 genes for intergenic transcripts.

Cytokine coexpression during human Th1/Th2 cell differentiation: direct evidence for coordinated expression of Th2 cytokines.

We have developed an in vitro differentiation assay in which human naive CD4(+) cells are driven toward either the Th1 or Th2 phenotype. We have examined the interrelationships among the expression of IL-2, IL-4, IL-5, IL-10, IL-13, GM-CSF, and IFN-gamma in individual cells using intracellular cytokine staining at various times during the differentiation process. We provide direct evidence that the Th2 cytokines IL-4, IL-5, and IL-13, unlike the other cytokines, are regulated by a coordinated mechanism.

DNA methylation changes at human Th2 cytokine genes coincide with DNase I hypersensitive site formation during CD4(+) T cell differentiation.

The differentiation of naive CD4(+) T lymphocytes into Th1 and Th2 lineages generates either cellular or humoral immune responses. Th2 cells express the cytokines IL-4, -5, and -13, which are implicated in asthma and atopy. Much has been published about the regulation of murine Th2 cytokine expression, but studies in human primary T cells are less common.