BackgroundAutoimmune diseases (AD) are a group of heterogeneous disorders caused by both genetic and environmental factors. Rheumatoid arthritis (RA) and Sjögrens syndrome (SS) are typical autoimmune diseases[1], Pulmonary fibrosis (PF) is the most common complication of AD. Despite the extensive study of the human gut microbiome in AD complicated with PF(AD-PF),the question of whether there are common microbial features characterizing AD-PF still remains[2].ObjectivesThis study focused on exploring differences between the microbiota diversity and peripheral lymphocyte subpopulations as well as cytokine in AD with PF is different from that of AD without PF.MethodsA total of 64 AD patients (44 AD without PF and 20 AD with PF) as well as 100 age- and sex- matched healthy controls (HCs) were enrolled in this study. The peripheral lymphocyte subsets were analyzed by flow cytometry and the gut microbiota were investigated via 16s rRNA sequencing. Alpha and Beta diversity (bray curtis distance-based) analysis was used to define the difference of gut microbiota profiles between patients and HCs. To explore the specific bacterial taxa associated with AD-PF, the STAMP software was used to compare the fecal microbiota composition. Spearman correlation analysis was used to determine the similarities in the microbiota community with clinical meatures among fecal samples.ResultsThere is a decrease that the richness and diversity index between HCs, AD and AD-PF patients. Principal co-ordinates analyses suggested that these three microbiota states explained a reasonable proportion of observed variance in gut microbiota composition (ANOSIM R2 = 0.113, p < 0.001; Figure 1b). Compared with HCs, there are obvious differences among 19 species of flora in AD without PF at the genus level, of which 2 species of flora (Lachnospira,Muribaculaceae) belong to AD-PF patients were showed much fewer. The relative abundance of Lachnospira was positive correlated with the absolute numbers of Th17, IL-6 and THF-α (P<0.05,Figure 1D-E)，which indicated Lachnospira may be the most critical among the AD-RF patients’ own species of flora. Therefore, the reduction of Lachnospira may influence the immune status of the intestinal tract of patients by producing less short-chain fatty acids.ConclusionOur results suggest that the decrease of Lachnospira may lead to the occurrence of AD with pulmonary interstitial fibrosis, which was closely correlated with lymphocyte subsets and Cytokines, maintaining the flora balance might be a potential therapeutic target for AD-PF.References[1]Ma Y, Shi N, Li M, Chen F, Niu H: Applications of Next-generation Sequencing in Systemic Autoimmune Diseases. Genomics Proteomics Bioinformatics 2015, 13(4):242-249.[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