Intimate neuro-immune interactions: breaking barriers between systems to make meaningful progress

•‘Non-immune’ cells (epithelia and neurons) exhibit properties of innate immunity.•Peripheral nerve activity modulates adaptive immune cell ontogeny and trafficking.•Peripheral nerves can initiate and suppress immune responses.•Abnormal neuro-immune signaling disrupts homeostasis and contributes to disease.•Biological systems are integrated, demanding interdisciplinary research approaches.