One of the exciting implications of gut health for autoimmune conditions is the role of gut microbes in regulating immune tolerance. The article by Miyauchi et al. describes how different gut microbe populations may be contributing to immune dysfunction that sustains autoimmunity, focusing on multiple sclerosis (MS), rheumatoid arthritis, type 1 diabetes, and lupus. Some highlights include:
- Gut microbe populations associated with extra-intestinal autoimmunity share in common that they promote the development of certain T cells (e.g., TH17) that are characteristically overactive in autoimmune conditions.
- The key T cell type that promotes tolerance and suppresses autoimmunity — the Treg cell — is reduced in people who have autoimmune conditions. Gut microbes that promote the development of Tregs are decreased in number in autoimmune conditions, and this may contribute to the observed lower activity of Treg cells.
- Components of some gut microbes can cross-react with human tissue components. This molecular mimicry may be another way that certain microbes initiate or drive autoimmune conditions. Evidence for autoantibodies that cross-react with parts of gut microbes has been found in patients with MS, rheumatoid arthritis, and lupus.
These observations suggest that modulating gut microbes may be an effective treatment for autoimmune conditions, but so far there is not much information on how effective this may be for patients. Findings from animal models are encouraging, however, as are studies in mice and humans showing that supplementing the diet with short-chain fatty acids such as propionate and butyrate (normally produced by the missing microbes) can improve symptoms in MS.
A key challenge identified in studies of modulating microbes to benefit autoimmunity is that there are marked individual differences between patients. Some people respond and some don't. Thus, to be effective, treatments will need to be tailored to each individual patient.
Overall, even though there is a ways to go before we have "tried and true" microbe-based interventions for autoimmunity, I feel the field is heading in the right direction.