By Rideeta Raquib ’19
The human gut is colonized by many microorganisms and each of them plays a role in maintaining various physiological functions, such as regulating digestion and fat absorption. It has been found that a vast number of inflammatory diseases around the world are associated with an instability of the gut microbiome. Researchers at the Mayo Clinic and University of Iowa suggest that gut commensals, bacteria that provide benefits such as fermenting dietary fiber and modulating immune responses, may be employed therapeutically to treat multiple sclerosis (MS), a deadly autoimmune disease. MS damages the myelin, a membrane that insulates nerves in the brain. As a result, the strength of the neural signals deteriorates; causing the affect individual to experience symptoms such as blurred vision and impaired coordination.
According to an animal model, known as experimental autoimmune encephalomyelitis (EAE), it is hypothesized that MS is caused by myelin-specific CD4 cells. CD4 is a type of T cell that recognizes antigens on surfaces of virus-infected cells. MS patients tended to show higher frequencies of human leukocyte antigen (HLA) class II haplotypes. HLA is a cell surface complex that is responsible for the regulation of the immune system. The researchers utilized transgenic mice that expressed human class II genes, as well as lacked endogenous class II genes to spot class II alleles that are prone to disease. The mice that expressed HLA-DR3 and DQ8 genes tended to develop EAE. After testing several bacteria commensal strains, it was discovered that Prevotella histicola had the ability to suppress disease by downregulating pro-inflammatory TH1/TH17 responses.
Overall, this study demonstrated that the human upper gastrointestinal tract contains commensals that have protective effects against diseases and neuroinflammation. This novel information can be expanded to treat other diseases that cause severe inflammatory responses.
- Ashutosh Mangalam, Shailesh K. Shahi, et al. Human Gut-Derived Commensal Bacteria Suppress CNS Inflammatory and Demyelinating Disease. Cell Reports, 2017; 20 (6): 1269 DOI: 10.1016/j.celrep.2017.07.031