The Brain-Immune-Gut Triangle: Innate Immunity in Psychiatric and Neurological Disorders

The communication between the immune and central nervous systems has been known for decades. Although the biological rules and complexity of the neuroimmune axis is yet to be clarified, in the modern era of immunology and clinical neurosciences it has become a dynamically evolving paradigm. In this review we trace the major findings of this emerging field with a special focus on innate immune cells and their phylogenetically conserved receptors, in line with their role in various psychiatric and neurological diseases. A particular interest will be given to monocytes, macrophages/microglia, dendritic cells, Toll-like and RIG-I-like receptors as well as their contribution to inflammation and other pathological processes in the CNS. Uncovering immunological mechanisms in the context of brain functions emerges as a promising avenue for future therapeutic interventions in various, still incurable ailments such as Alzheimer’s disease, schizophrenia, or different mood disorders such as major depression or bipolar disorder. We propose new perspectives for the pharmacological modification of innate immune cells and their response to inflammatory cues in the brain. A holistic concept of studying the gut-brain-immune triangle is also suggested to bring up novel approaches in immunology, gastroenterology, psychiatry and neurology.