Nerve injuries can lead to hidden immune changes throughout the entire body

Nerve injuries are common and can occur as a result of stretching, compression, or cuts. They often lead to persistent problems such as chronic pain. Although the immune system normally works to repair damaged tissue, the new findings suggest that nerve injuries can also alter immune activity throughout the entire body.

Laboratory analysis of blood taken from mice showed clear evidence of inflammation throughout the body after nerve injury. The researchers also found that males and females did not respond in the same way.

Distinctive immune patterns in males and females

In male mice, markers of inflammation in the bloodstream increased and remained elevated. In female mice, these markers did not increase at all. However, when blood from infected males or females was transferred to healthy mice, it resulted in increased sensitivity to pain in both cases. According to the researchers, this means that something in the bloodstream – although not the same in males and females – is able to spread pain responses throughout the body.

“This means that whatever causes pain in females operates through a completely different biological pathway that we don’t yet understand,” said co-author Jeffrey Mogill, professor of pain studies at McGill University and the James McGill Distinguished Professor.

“By understanding how men and women react differently to nerve injuries, we can work toward more personalized and effective treatments for chronic pain,” added Sam Chu, lead author of the study and a doctoral student at McGill University.

Wider health implications

Researchers report that nerve injuries may affect much more than the damaged site. Long-term disturbances in immune function can increase the likelihood of chronic pain and may contribute to related conditions such as anxiety and depression.

“Recognizing the full impact of nerve injuries is important for both doctors and patients,” said Dr. Jie Zhang, lead researcher and professor in the Department of Neurology and Neurosurgery and the Faculty of Dentistry and Oral Health Sciences at McGill University. “Local nerve injury can affect the entire body. Men and women may respond differently.”

“The effect of nerve injury on the immune system across the lifespan is sexually dimorphic” by Sam Zhu, Xiang Shi, Alan Zhang, Magali Melcamps, Jeffrey Mogil and Ji Zhang Published in Neurobiology of pain. The study was funded by the Canadian Institutes of Health Research and the Louise and Alan Edwards Foundation.