Immune drivers of pain resolution and protection

Immune cells are involved in the pathogenesis of pain by directly activating or sensitizing nociceptor sensory neurons. However, because the immune system also has the capacity to self-regulate through anti-inflammatory mechanisms that drive the resolution of inflammation, it might promote pain resolution and prevention. Here, we describe how immune cell-derived cytokines can act directly on sensory neurons to inhibit pain hypersensitivity and how immune-derived endogenous opioids promote analgesia. We also discuss how immune cells support healthy tissue innervation by clearing debris after nerve injury, protecting against axon retraction from target tissues and enhancing regeneration, preventing the development of chronic neuropathic pain. Finally, we review the accumulating evidence that manipulating immune activity positively alters somatosensation, albeit with currently unclear molecular and cellular mechanisms. Exploration of immune-mediated analgesia and pain prevention could, therefore, be important for the development of novel immune therapies for the treatment of clinical pain states. Woolf and colleagues review the current evidence that immune cells could promote pain resolution and prevention through direct effects on sensory neurons and through maintaining healthy tissue innervation.