Yuning Peng,Huanrong Tang,Hao Xiao,Wenyuan Chen,Jingdong Song,Jing Zheng,Hongrong Liu
T5 is a siphophage that has been extensively studied by structural and biochemical methods. However, the complete in situ structures of T5 before and after DNA ejection remain unknown. In this study, we used cryo-electron microscopy (cryo-EM) to determine the structures of mature T5 (a laboratory-adapted, fiberless T5 mutant) and urea-treated empty T5 (lacking the tip complex) at near-atomic resolutions. Atomic models of the head, connector complex, tail tube, and tail tip were built for mature T5, and atomic models of the connector complex, comprising the portal protein pb7, adaptor protein p144, and tail terminator protein p142, were built for urea-treated empty T5. Our findings revealed that the aforementioned proteins did not undergo global conformational changes before and after DNA ejection, indicating that these structural features were conserved among most myophages and siphophages. The present study elucidates the underlying mechanisms of siphophage infection and DNA ejection.
Decidual CD8 + T (dCD8 + T) cells are pivotal in the maintenance of the delicate balance between immune tolerance towards the fetus and immune resistance against pathogens. The endometrium and decidua represent uterine environments before and during pregnancy, respectively, and the composition and phenotypic alterations of uterine CD8 + T cells in these tissues remain unclear. Using flow cytometry and analysis of transcriptome profiles, we demonstrated that human dCD8 + T and endometrial CD8 + T (eCD8 + T) cells exhibited similar T cell differentiation statuses and phenotypes of tissue infiltrating or residency, compared to peripheral CD8 + T (pCD8 + T) cells. However, dCD8 + T cells showed decreased expression of coinhibitory (PD-1), chemotaxis (CXCR3), and tissue-resident (CD69 and CD103) markers and increased granzyme B and granulysin expression compared to eCD8 + T cells. In vitro, cytotoxicity assays demonstrated greater effector functions in dCD8 + T cells than in eCD8 + T cells. Further in vitro and in vivo chemotaxis assays confirmed the recruitment of non-resident effector memory T cell subsets to the pregnant decidua, contributing to the dCD8 + T cell-mediated anti-infection mechanism at the maternal-fetal interface. This work demonstrated dCD8 + T cells replenished from the circulation retained their cytotoxic capacity, which may serve as an enhanced defense mechanism against infection during pregnancy.
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