A protective role of bifidobacteria in the pathogenesis of MS—and also of Guillain-Barré syndrome (GBS)—was hypothesized by Shi et al. [68]: a lower level of bifidobacteria has been negatively correlated with the levels of IL-17A in cerebrospinal fluid (CSF) and plasma samples of patients. The gene discussed is IL17A; the disease is Guillain-Barre syndrome.