The human body is an incredibly complex system, and from time immemorial, humans have struggled to work out what the gut and brain have to do with health and whether the 2 are connected. The parallels between the gut’s and the brain’s immune systems are too self-evident to deny. The similarities extend to the actual structures, mechanisms, and even biochemistries of the 2 systems: the gut immune barrier (GIB) and the blood-brain barrier (BBB). Bidirectional signaling between the brain and the gut has been confirmed by numerous studies. In fact, the communication between the gut and the brain is ongoing from birth and plays a significant role in shaping how the brain is wired. The gut’s influence on the brain cannot be overestimated, so much so that it can be called a second brain. Studies have linked gut-microbiota dysbiosis to brain-linked disorders, such as depression, anxiety, multiple sclerosis, and autism. The scientific community is aware now that neurodegenerative diseases may not exclusively have a neurological trigger. Uncontrolled chronic inflammation, disturbances in the gut microbiota, and other gastrointestinally related dysfunctions have been linked to neurodegenerative disorders. A spotlight has been focused on the role of intestinal-barrier function in the pathogenesis not only of gastrointestinal diseases but also of autoimmune, neuroautoimmune, and neurodegenerative ones. Using predictive antibodies opens the possibility of prevention, amelioration, and even reversal of autoimmune disorders, both gastrointestinal and neurodegenerative, through treatment modalities that involve the repair of the GIB and BBB, thus restoring the functionality of their barriers and the stability of their environments.