Intestinal microbiome adjusts the innate immune setpoint during colonization through negative regulation of MyD88

Bjørn E V Koch,Gerda Lamers,Herman P Spaink,Shuxin Yang,Jens Stougaard

doi:10.1038/s41467-018-06658-4

Abstract

Host pathways mediating changes in immune states elicited by intestinal microbial colonization are incompletely characterized. Here we describe alterations of the host immune state induced by colonization of germ-free zebrafish larvae with an intestinal microbial community or single bacterial species. We show that microbiota-induced changes in intestinal leukocyte subsets and whole-body host gene expression are dependent on the innate immune adaptor gene myd88. Similar patterns of gene expression are elicited by colonization with conventional microbiome, as well as mono-colonization with two different zebrafish commensal bacterial strains. By studying loss-of-function myd88 mutants, we find that colonization suppresses Myd88 at the mRNA level. Tlr2 is essential for microbiota-induced effects on myd88 transcription and intestinal immune cell composition.

Highlights

Several animal studies point to the toll-like receptor (TLR) pathway as central in many aspects of host sensing of the microbiome[8,9,10,11]
Previous observations in zebrafish larvae have found neutrophil presence in the intestine to be lowest in germ-free larvae as compared to colonized groups at 6 DPF9,27
As L-plastin, the antigen targeted in our experiments, is a general leukocyte marker, this approach cannot distinguish macrophages from neutrophils

Summary

Introduction

Several animal studies point to the toll-like receptor (TLR) pathway as central in many aspects of host sensing of the microbiome[8,9,10,11]. Several observations support the importance of TLR signaling to host intestinal immune homeostasis, as mouse mutants of specific TLRs have been found to develop inflammatory intestinal conditions without pathogenic challenge[19,20]. Seemingly conflicting observations have been reported as another recent study found improved intestinal immune responses to a high fat diet in a Myd[88] deficient mouse mutant[21]. Utilizing fluorescent reporter fish lines, immunostaining, and genetic mutants we characterize the intestinal innate immune response to bacterial colonization and investigate the role of Myd[88] in mediating these effects. Using RNAseq we characterize and compare the effects of colonization at different levels of microbial community complexity, and in the presence or absence of a functional Myd[88] encoding gene. Our data reveal aspects of myd[88] transcription controlled by microbial colonization through Tlr[2] mediated sensing

Methods

Results

Conclusion