BackgroundAn increasing number of autoimmune disorders (AD) have been associated with microbial dysbiosis[1, 2]. However, this dysbiosis is difficult to characterize for individual patients owing to the high heterogeneity of the gut microbiota. Thus, researchers must find an accurate method of characterizing the AD gut microbiota that is meaningful to clinical diagnosis.ObjectivesThe aim of this study was to investigate the enterotype characters of intestinal flora in AD and their associations with peripheral lymphocyte subpopulations and cytokines.MethodsA total of 339 AD patients and 339 age- and sex- matched healthy controls (HCs) were enrolled in this study. Mathematical modeling using Dirichlet multinomial mixtures (DMM) was applied to describe the variability in the microbiome data and cluster samples into enterotypes. The peripheral lymphocyte subsets were detected by flow cytometry and the cytokines were assessed by ELISA. Differential abundance analysis was carried out the STAMP software. R (version 4.1.0) was used for comparative statistics, and spearman’s correlation analysis was used to assess the correlations between the relative abundances of bacterial genera and clinical variables.ResultsLaplace approximation of DMM suggested gut microbiota of AD patients and HCs both can be divided into two distinct enterotypes (Figure 1 A-B), and AD E1 and HC E1 were primarily dominated by Prevotella while AD E2 and HC E2 by Bacteroides. Interestingly, the Prevotella-enriched enterotype (AD E1 and HC E1) had a higher alpha diversity than The Bacteroides-enriched enterotype (AD E2 and HC E2). Patients with AD always had a lower richness and diversity compared with those of HCs in each enterotype (p< 0.001), suggesting gut microbiome was markedly less diverse in composition in AD. Bray curtis distance-based beta-diversity were also different (P<0.001, ANOSIM.R =0.23, Figure 1 C-H). Significant differences in gut microbiota composition at the genus level between AD patients and HCs were found using the STAMP software in each enterotype. Compared with HCs, 37 species in AD E1 patients and 40 species in AD E2 patients of flora were discovered to be distinctly different. In the co-upregulated flora of both enterotypes, Lactobacillus was inversely associated with a variety of lymphocytes such as T, CD4+T, NK, Th2, Th17, Treg cells(P<0.05), and positive correlation with IL-10 and IFN-γ(P<0.05,Figure 1 I). However, in the co-downregulated floras Coprococcus had a positive correlation with B, NK and Treg cells, and anaerostipes had a negativate corrleation with IL-2 and IL-4(P<0.05,Figure 1 J).ConclusionThere were both two enterotypes in patients and HCs with autoimmune disease, E2 exhibited a loss of Prevotella but a growth of Bacteroides, while E1 presented the opposite results, which were closely correlated with peripheral lymphocyte subsets and cytokines.References[1]Levy M, Thaiss CA, Zeevi D, Dohnalová L, Zilberman-Schapira G, Mahdi JA, David E, Savidor A, Korem T, Herzig Y et al: Microbiota-Modulated Metabolites Shape the Intestinal Microenvironment by Regulating NLRP6 Inflammasome Signaling. Cell 2015, 163(6):1428-1443.[2]Belkaid Y, Hand TW: Role of the microbiota in immunity and inflammation. Cell 2014, 157(1):121-141.AcknowledgementsThis work was supported by the National Natural Science Foundation of China (No. 82001740).Disclosure of InterestsNone declared

BackgroundAnkylosing spondylitis (AS) is an immune-mediated inflammatory arthritis that affects the axial skeleton. Currently, the cause of AS is still not known, so there is no way to prevent AS. Interleukin-7 (IL-7) is a restrictive and non repetitive cytokine, mainly produced by epithelial and stromal cells. The relationship between IL-7 and some inflammatory cytokines such as AS has been discussed in recent advances in the pathogenesis of AS, but a direct effect of IL-7 on AS has not been demonstrated[1].ObjectivesStudy to investigate the casual association between IL-7 and AS.MethodsWe evaluated the causal relationship between IL-7 levels and AS using a Mendelian randomization approach. The GWAS summary statistics of IL-7 (N = 3409) and AS (Ncase = 968, Ncontrol = 336,191) were downloaded from the IEU GWAS database in the study. Instrumental variables (IVs) were constructed using single nucleotide polymorphisms (SNPs). To assess the causal relation of IL-7 and AS, we used three analytical methods: MR-Egger mode, Weighted median mode, and Inverse variance weighted (IVW). In addition, we also conducted sensitivity tests, including the heterogeneity test, the pleiotropy test, the funnel plot, leave-one-out approach and MR-PRESSO.ResultsWhen selecting SNPs associated with IL-7, in the situation of the genome-wide significant threshold of P < 5×10-6 and LD r2 = 0.001, we finally obtained 9 IVs that could be used in the subsequent steps. Based on the IVW mode with high statistical power, a prudent and credible causal relationship was demonstrated between IL-7 and AS [IVW: P=0.025, OR(95%CI)=0.999(0.999, 1.000)]. As the level of IL-7 increased, the risk of developing AS also decreased, proving that IL-7 was a protective factor for this disease (Figure 1a). The Cochrane Q test (Q test p = 0.99) showed a good homogeneity among studies. The results of a leave-one-out sensitivity analysis suggested that causal associations were not strongly influenced by any of the selected IVs (Figure 1b). Funnel plot results (Figure 1c) and the intercept of the MR-Egger regression (Figure 1d) further showed that pleiotropy did not bias the causal effect in this study.ConclusionOur research results show that IL-7 is causally associated with the pathogenesis of AS. which enables the early detection of AS, this findings have great clinical value.Reference[1]Pedersen SJ, Maksymowych WP. The Pathogenesis of Ankylosing Spondylitis: an Update. Curr Rheumatol Rep. 2019;21(10):58 ‘doi’: 10.1007/s11926-019-0856-3[‘2019-11-11].AcknowledgementsThis work was supported by the Key R&D Program of Shanxi Province(201903D311011) and Taiyuan Science and Technology Plan (XG2020-5-06).Disclosure of InterestsNone Declared.