When your body suffers trauma, its fierce army of immune cells go to work — clearing out dead and damaged tissue as well as beefing up the injured area’s defense against infection. But for the some 12,000 new cases of spinal cord injury in the US annually, the body’s immune system can often do more harm than good, causing nerve damage, numbness, even paralysis.

With this in mind, scientists at the University of Michigan set out to find a way around this over-reactive immune response, and discovered that an injection of nanoparticles directed to suppress immune cells could become the “EpiPen” of spinal trauma.

“In this work, we demonstrate that instead of overcoming an immune response, we can co-opt the immune response to work for us to promote the therapeutic response,” says Lonnie Shea, biomedical engineering professor at UM, whose research has been published in the Proceedings of the National Academy of Sciences.

The central nervous system, which includes the spinal cord, is usually protected from our aggressive immune activity thanks to the blood-brain barrier — a complex of endothelial cells that help block toxins, pathogens and other dangerous substances from impacting our nervous system, and prevents overzealous immune cells from causing a dangerous amount of inflammation to fragile nerve tissues.

However, spinal trauma often leads to a break in this barrier, causing rapid death of neurons, nerve damage that inhibits them from sending signals throughout the body and scar-tissue formation which prevents regeneration of nerve cells — leaving patients worse off, even after the injury itself is fixed.

Physicians used to use steroids such as methylprednisolone to quell immune activity after a spinal injury — similar to how an EpiPen is used to quell an allergic reaction — but this method was scrapped due to its complicating side effects, such as sepsis, gastrointestinal bleeding and clots.

This new discovery, on the other hand, employs non-pharmaceutical nanoparticles that redirect potentially harmful immune cells away from the spinal cord injury, while allowing the more helpful ones in to work the repairs. Because the nanoparticles aren’t attached to drugs, scientists believe that unwanted side effects often associated with pharmaceuticals will be avoided.

Meanwhile, fewer immune cells will cause less inflammation and deterioration of nerve tissue.

“Hopefully, this technology could lead to new therapeutic strategies not only for patients with spinal cord injury but for those with various inflammatory diseases,” says UM research fellow Jonghyuck Park.

In the past, nanoparticles have also been shown to reduce trauma caused by West Nile virus and multiple sclerosis.

“The immune system underlies autoimmune disease, cancer, trauma, regeneration — nearly every major disease,” says Shea. “Tools that can target immune cells and reprogram them to a desired response have numerous opportunities for treating or managing disease.”