Immunology and the Microbiome

The human body, inside and out, is covered in microbes, with the bulk of them lining the intestinal walls. Recent research is examining the relationship between microbes and the body and the ways in which this relationship impacts the immune system. Although this research is still in the early stages, some researchers and clinicians believe that the microbiome could become a cornerstone of autoimmune disease treatment.¹

Microbiota are implicated in almost every chronic condition, including autoimmune conditions. Imbalance among the gut microbiota may drive inflammatory conditions such as obesity, diabetes, inflammatory bowel disease, colorectal cancer, and immunosenescence in the elderly,² as well as endocrine diseases.³ The accumulation of microbes that are perceived as pathogens in the microbiome likely contributes to the inflammatory cascade that impacts immune function and tolerance.⁴

Sensitive periods for the microbiome include childhood and pregnancy, during which the microbiome may undergo profound changes.⁵ A 2012 study suggests that differences exist in pregnant women between their first and third trimesters; in the last months of pregnancy, researchers noticed an abundance of Proteobacteria and Actinobacteria and a depletion of Faecalibacterium (a butyrate producer with anti-inflammatory effects). During childhood, the gut microbiome may be influenced by environmental factors such as geographic area, breastfeeding, exposure to antibiotics, and method of delivery. Vaginally delivered infants acquire bacterial communities resembling their own mother’s vaginal microbiota (Lactobacillus, Prevotella, Sneathia spp.), while Cesarean section–delivered infants harbor bacterial communities similar to those found on the skin surface (Staphylococcus, Corynebacterium, and Propionibacterium). These types of alterations in the microbiome may trigger both local and systemic inflammation.⁵

This line of research points to the potential for treatment and prevention of autoimmune conditions using therapies directed at the microbiome, as the loss of immune tolerance can be caused by microbial composition changes. A recent review article described a number of exciting studies focused on the microbiome, therapeutic probiotics, and autoimmune conditions, including systemic lupus erythematosus (SLE), type 1 diabetes, and more.^6,7 Even central nervous system autoimmune conditions may benefit from treatments that target the microbiome and its activity.⁸

In one surprising study, researchers found that bacteria in the small intestines of mice and humans can travel to other organs, where they may trigger an autoimmune response.⁹ The researchers also found that this autoimmune reaction can be suppressed with antibiotic treatment or vaccines designed to target the bacteria. These findings offer a new understanding of and exciting promise for the treatment of autoimmune conditions such as SLE and autoimmune liver disease.⁹