Over the last decade, the interplay between the gut microbiota, the consortium of intestinal microbes that colonizes intestinal mucosal barriers, and its host immune system has been increasingly better understood. Disruption of the delicate balance between beneficial and pathogenic commensals, known as dysbiosis, contributes to a variety of chronic immunologic and metabolic diseases. Complicating this paradigm are bacterial strains that can operate paradoxically both as instigators and attenuators of inflammatory responses, depending on host background. Here, we review the role of several strains in the genus Lactobacillus within the context of autoimmune and other chronic disorders with a predominant focus on L. reuteri. While strains within this species have been shown to provide immune health benefits, they have also been demonstrated to act as a pathobiont in autoimmune-prone hosts. Beneficial functions in healthy hosts include competing with pathogenic microbes, promoting regulatory T cell development, and protecting the integrity of the gut barrier. On the other hand, certain strains can also break through a dysfunctional gut barrier, colonize internal tissues such as the spleen or liver and promote inflammatory responses in host tissues that lead to autoimmune disease. This review summarizes the manifold roles that these commensals play in the context of health and disease.
Keywords: Autoimmunity; Dysbiosis; E. gallinarum; Endosomal TLR7; Gut microbiome; L. johnsonii; L. reuteri; Lactobacillus; P. copri; R. intestinalis; Resistant starch diet; Translocation; Type I interferon.
© 2020 Elsevier Inc. All rights reserved.
A Diet-Sensitive Commensal Lactobacillus Strain Mediates TLR7-Dependent Systemic Autoimmunity.Cell Host Microbe. 2019 Jan 9;25(1):113-127.e6. doi: 10.1016/j.chom.2018.11.009. Epub 2018 Dec 20. Cell Host Microbe. 2019. PMID: 30581114 Free PMC article.
Lactobacillus johnsonii N6.2 mitigates the development of type 1 diabetes in BB-DP rats.PLoS One. 2010 May 6;5(5):e10507. doi: 10.1371/journal.pone.0010507. PLoS One. 2010. PMID: 20463897 Free PMC article.
Mechanisms and consequences of gut commensal translocation in chronic diseases.Gut Microbes. 2020;11(2):217-230. doi: 10.1080/19490976.2019.1629236. Epub 2019 Jul 15. Gut Microbes. 2020. PMID: 31306081 Free PMC article.
Role of Lactobacillus reuteri in Human Health and Diseases.Front Microbiol. 2018 Apr 19;9:757. doi: 10.3389/fmicb.2018.00757. eCollection 2018. Front Microbiol. 2018. PMID: 29725324 Free PMC article. Review.
Impact of gut microbiota on gut-distal autoimmunity: a focus on T cells.Immunology. 2019 Apr;156(4):305-318. doi: 10.1111/imm.13037. Epub 2019 Jan 21. Immunology. 2019. PMID: 30560993 Free PMC article. Review.