Abstract: Objective To investigate the pro-inflammatory function and mechanisms of γδ T cells derived from intestinal intraepithelial lymphocytes (IELs) in a mouse model of inflammatory bowel disease (IBD) induced by dextran sulfate sodium (DSS). Methods Mouse model of IBD was established by DSS administration in both γδ T cell knockout (KO) mice and in wild-type (WT) mice. Intestinal tissue damage was evaluated by the disease activity index (DAI) and hematoxylin-eosin (HE) staining microscopy. Flow cytometry was employed to analyze the proportion, subset composition, cytokine secretion, and surface cluster of differentiation (CD27) expression of γδ T cells isolated from the spleen(SPL), peripheral lymph nodes(LNs) and IEL.Bulk RNA sequencing(bulk RNA-seq) was performed to examine transcriptomic changes while and immune repertoire sequencing was used to evaluate the character of TCRγδ repertoire. Results Compared to WT controls, γδ T cell KO mice exhibited lower DAI scores(P＜0.05) and milder tissue damage following DSS administration. The proportion of γδ T cells in the IEL was higher than that in the spleen or peripheral lymph nodes but significantly increased after DSS treatment(P＜0.05). The relative proportions of Vγ1 and Vγ4 subsets,IFN-γ and IL-17 secretion, and surface CD27 expression did show any significant difference between untreated and DSS-treated groups. However, bulk RNA-seq analysis revealed a down regulation of anti-bacterial molecule genes and anti-inflammatory genes in DSS-treated mice(P＜0.05).Immune repertoire analysis showed that complementarity determining region(CDR)3 diversity in γδ T cells from DSS-induced mice was reduced significantly(P＜0.05). Conclusions IEL-derived γδ T cells promote intestinal inflammation in DSS-induced colitis via mechanisms that appear independent of pro-inflammatory cytokine secretion. These cells exhibit reduced inflammation-associated CDR3 diversity, impaired anti-microbial pathway activity, and disrupted immunoregulatory signaling. The results of this research may support the development of novel therapeutic strategies for IBD.

Key words: inflammatory bowel disease(IBD), γδ T cell, intestinal intraepithelial lymphocyte(IEL), bulk transcriptomic sequence, immune repertoire