The Central Nervous System is protected from physical trauma and invading pathogens by the surrounding meninges. Meninges contain a variety of innate and adaptive immune cells, such as the T cells, dendritic cells, mast cells, and meningeal macrophages as a defence against pathogens. However, not many studies have focused on B cells. Increased levels of IgG and IgA antibodies have been observed in various diseases states of the CNS. Previously believed to be a result of systemic production and transport through the blood to the brain, newer evidence establishes the existence of localized populations of IgA producing plasma cells in the meninges.
IgA in the gut maintains barrier integrity by preventing their entry through the epithelium and trapping them in the mucus layer. The slow blood flow and low shear forces in the dural venous sinuses make it susceptible to invasion by bloodborne pathogens. Thus the localisation of IgA producing plasma cells in the dural sinuses is a protective measure against the invading pathogens.
Further research suggests that these plasma cells train in the intestines and then migrate to the meninges. What is even more interesting is that the population of IgA producing cells is dependent on the microbiome present in the gut. A depletion in the gut microbiome resulted in a significant reduction in the meningeal B cells. It was also observed that different microbiomes of varying bacterial diversity resulted in a variation of the meningeal plasma cell population. A breach in the intestinal barrier resulted in an increase in meningeal IgA producing plasma cells.
Thus maintaining a healthy gut flora aids the body in more than just digestion.
Fitzpatrick, Z., et al.,(2020). Gut-educated IgA plasma cells defend the meningeal venous sinuses. Nature, 587(7834), 472–476. https://doi.org/10.1038/s41586-020-2886-4
