Cell：宿主特异性微生物丛诱导免疫系统成熟

6月21日，Cell杂志报道了宿主特异性微生物丛在诱导免疫系统成熟过程中作用的重要研究进展。

肠道微生物诱导宿主的免疫系统成熟，充分体现了宿主 - 微生物共生关系。研究者移植小鼠微生物丛（MMB）或人类微生物丛（HMB）到无微生物（GF）小鼠小肠中，以确定是否小肠免疫成熟取决于宿主特异性的微生物共同进化。

研究显示，肠道细菌的数量和细菌分类门 (phylum)的丰度在MMB和HMB小鼠小肠中是类似的，但细菌种类不同，尤其是厚壁菌门细菌的含量不同。 HMB小鼠肠道有低水平的CD4 +和CD8 + T细胞；增殖T细胞和树突状细胞也很少；同时，抗菌肽的表达也比较低。这些都是类似于GF小鼠的特点。

大鼠的微生物丛也未能充分扩大小鼠肠道T细胞的数量。给GF或HMB小鼠移植小鼠分段丝状菌（SFB）可部分恢复T细胞数量。这表明SFB和其他MMB微生物是诱导小鼠免疫功能充分成熟所必需的。重要的是，MMB比HMB能更好地保护小鼠免受沙门氏菌感染。可见，宿主特异性微生物丛，对于一个健康的免疫系统是何等地关键！

这项研究，也为防止滥用抗生素，维护正常肠道菌群带来很大的启发。

doi:10.1016/j.cell.2011.10.017
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Gut Immune Maturation Depends on Colonization with a Host-Specific Microbiota

Hachung Chung, Sünje J. Pamp, Jonathan A. Hill, Neeraj K. Surana,et al

Gut microbial induction of host immune maturation exemplifies host-microbe mutualism. We colonized germ-free (GF) mice with mouse microbiota (MMb) or human microbiota (HMb) to determine whether small intestinal immune maturation depends on a coevolved host-specific microbiota. Gut bacterial numbers and phylum abundance were similar in MMb and HMb mice, but bacterial species differed, especially the Firmicutes. HMb mouse intestines had low levels of CD4+ and CD8+ T cells, few proliferating T cells, few dendritic cells, and low antimicrobial peptide expression—all characteristics of GF mice. Rat microbiota also failed to fully expand intestinal T cell numbers in mice. Colonizing GF or HMb mice with mouse-segmented filamentous bacteria (SFB) partially restored T cell numbers, suggesting that SFB and other MMb organisms are required for full immune maturation in mice. Importantly, MMb conferred better protection against Salmonella infection than HMb. A host-specific microbiota appears to be critical for a healthy immune system.