A report is presented of SHRIMP zircon U-Pb dating data of meta-igneous and meta-sedimentary rocks of the Xinghuadukou Group (Xinlin-Hanjiayuanzi area, Heilongjiang Province) and meta-volcanic rocks of the Zhalantun Group (Zhalantun district, Inner Mongolia). The SHRIMP analyses show that the meta-igneous rocks from the Xinghuadukou Group formed at 506±10-547±46 Ma, belonging to Early-Middle Precambrian, whereas the meta-sedimentary rocks yielded detrital zircons, with ages of 1.0 -1.2, 1.6 -1.8 and 2.5 -2.6 Ga, indicative of deposition age at least <1.0 Ga.
Meta-basic volcanic rocks from the Zhalantun Group have a formation age of 506±3 Ma. These data suggest that both the Xinghuadukou and Zhalantun Groups formed during Cambrian and/or Neoproterozoic time, rather than Paleoproterozoic time as previously thought. Early Precambrian inherited zircons in the meta-igneous rocks and numerous Precambrian detrital zircons inthe meta-sedimentary rocks imply that these rocks were formed proximal to older crust. It is inferred that the Xinghuadukou and Zhalantun Groups represent Cambrian and/or Neoproterozoic volcano-sedimentary sequences formed in an active continental margin setting.
Functional exhaustion of antigen-specific T cells is a defining characteristic of many chronic infections, but the underlying mechanisms of T cell dysfunction are not well understood. Epigenetics plays an important role in the control of T cell development, differentiation, and function. To examine if epigenetics also plays a role in T cell exhaustion, we analyzed chromatin remodeling in CD8(+) T cells from mice with chronic lymphocytic choriomeningitis virus infection. We observed downregulation of diacetylated histone H3 in both virus-specific and total CD8(+) T cells, and functional defects not only in virus-specific CD8(+) T cells but also within the total CD8(+) T cell population. In vitro treatment of these exhausted CD8(+) T cells with histone deacetylase inhibitors restored diacetylated histone H3 levels, and improved their immune functions. Upon adoptive transfer, these treated CD8(+) T cells developed into functional memory T cells in vivo that enhanced protective immunity. These results define a role of epigenetics in T cell exhaustion and suggest epigenetic manipulation as a novel molecular therapy to restore immune functions.
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