Figure 10.

Working hypothesis of communication between the CNS and gut microbiota mediated by immune system. Acute or chronic CNS infection TMEV results in inflammation of the gray matter or white matter of the spinal cord, leading to diseases mimic acute flaccid myelitis (AFM) or multiple sclerosis (MS), respectively. Alteration of a limited number of distinct bacteria in gut microbiota was associated with different immune gene expressions during the acute and chronic phases. The genus Marvinbryantia abundance correlated with gene expressions of distinct T-cell receptors (TCR) and immunoglobulin (Ig) A during the acute phase and those of Igs during the chronic phase. The genus Coprococcus abundance was associated not only TCR and Ig (IgG isotypes and IgA) but also other immune related genes, including major histocompatibility complex (MHC) and complements (C'). Here, alteration of a small number of gut bacteria may affect distinct immune responses and then lesions in the CNS, although we do not know the precise pathophysiology, particularly the CNS upregulation of IgA, which is a component of mucosal immunity. Alternatively, activated immune response would alter composition of gut microbiota.