Lamina propria Interleukin 17 A aggravates natural killer T cells activation in autoimmune hepatitis

Autoimmune hepatitis is an interface hepatitis characterized by the progressive destruction of the liver parenchyma, the cause of which is still obscure. Interleukin (IL)-17A is a major driver of autoimmunity, which can be produced by innate immune cells against several intracellular pathogens. Here, we investigated the involvement of IL-17A in a mice model of immune-mediated hepatitis with the intestine exposed to Salmonella typhimurium. Our results showed more severe Concanavalin (Con) A-induced liver injury and gut microbiome dysbiosis when the mice were treated with a gavage of S. typhimurium. Then the Natural Killer (NK) T cells were over-activated by the accumulated IL-17A in the liver in the Con A and S. typhimurium administration group. IL-17A could activate NKT cells by inducing CD178 expression via IL-4/STAT6 signaling. Furthermore, via the portal tract, the laminae propria mucosal-associated invariant T (MAIT) cell-derived IL-17A could be the original driver of NKT cells' over-activation in intragastric administration of S. typhimurium and Con A injection. In IL-17A deficient mice, Con A-induced liver injury and NKT cells activation was alleviated. However, when AAV-sh-mIL-17a was used to specifically knock down IL-17A in liver, it seemed that hepatic IL-17a knock down did not significantly influence the liver injury. Our results suggested that, under Con A-induction, laminae propria MAIT-derived IL-17A activated hepatic NKT, and this axis could be a therapeutic target in autoimmune liver disease. Overall design: Total genome DNA from murine luminal samples from ileocecus was extracted for amplification using the V4 regions (Qiagen, USA) (20). Sequencing libraries were prepared using the TruSeq® DNA PCR-Free Sample Preparation Kit (Illumina, USA) following the manufacturer's recommendations. The library quality was evaluated on the Qubit@ 2.0 Fluorometer (Thermo Scientific, USA) and Agilent Bioanalyzer 2100 system (Agilent Technologies, USA). At last, the library was sequenced on an Illumina platform (Illumina, USA), and 250 bp paired-end reads were generated. The 16S rDNA gene sequence data were processed using the QIIME (V1.7.0) with default parameters (21). Sequences analysis was performed by Uparse software (Uparse v7.0.1001) (22). Sequences with =97% similarity were assigned to the same operational taxonomic units (OTUs). The representative sequence for each OTU was screened for further annotation. The output data were further analyzed using Statistical Analysis of Metagenomic Profiles (STAMP) software version 2.1.3