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Science  19 Mar 2004:
Vol. 303, Issue 5665, pp. 1731
DOI: 10.1126/science.303.5665.1731c

Differentiation of CD4+ helper T cells is described as taking one of two routes: Naive T cells can become either T helper type 1 (TH1) cells or TH2 cells, with distinctive patterns of cytokine expression. Looking at genome-wide transcriptional profiles of helper T cells at different stages of differentiation, Lu et al. observed that of the distinct sets of transcribed genes, those regulating replication became prominent soon after activation, while resting-state genes were silenced. This led the authors to suggest that a large-scale increase in chromatin accessibility accompanying early events would allow transcription factors to coordinate the expression of genes needed to secure the subsequent differentiation of the helper T cell.

Cote-Sierra et al. reexamined the specific role of interleukin-2 (IL-2) in TH2 differentiation. In contrast to the previously held assumptions that this cytokine acts simply as a growth factor for differentiating T cells, IL-2 appeared to assist directly the differentiation process by stabilizing the accessibility of the IL-4 locus. Both studies suggest that factors influencing activation and proliferation also set the stage for transcription events that secure the fate of the T cell. — SJS

Proc. Natl. Acad. Sci. U.S.A. 101, 3023; 3880 (2004).

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