Figure 1.

Contribution of different immune cells to pain development and recovery. CD4⁺ T helper cells were shown to infiltrate the spinal cord, DRG and injured nerve, where they contribute to pain responses through different mechanisms. Further, DRG invading macrophages were shown to be important mediators of pain. Like T effector cells, Tregs infiltrate the nerve, DRG, and spinal cord in neuropathic mice and contribute to immunomodulation and tissue regeneration through different mechanisms, including secretion of anti-inflammatory IL-10. M2 macrophages were shown to initiate analgesic responses in the nerve through upregulation of the endogenous opioid system and anti-inflammatory responses.