Researchers investigate why immune system is blunted after spinal cord injury

Mar 4 2011

Mobility is a challenge for spinal cord injured patients. Infection is another. Adam Thrasher, assistant professor of health and human performance (HHP), says infection is the leading cause of death for people living with spinal cord injuries for two years or more. He and HHP colleague Richard Simpson are investigating why the immune system is blunted after a spinal cord injury.

"People who have sustained such an injury have much higher infection rates than the general population, particularly in the urinary tract, lungs and gastro-intestinal tract," Thrasher said. "They are very susceptible to pneumonia and furthermore, because their immune system is compromised, they have a hard time fighting these infections."

There are many theories as to why exercise helps an able-bodied person's immune system. The body may respond to exercise by releasing more antibodies and white blood cells, allowing them to find and fight illnesses before they become problematic, or the reduction in stress may assist the body in staving off illness. Though many theories exist for the able-bodied population, there are few for those with spinal cord injuries.

"It's a bit of a mystery because the injury is to the central nervous system," Thrasher said. "This is the part of the body that controls different muscles and organs. We know that there is paralysis; we know that there are limits to their mobility. But the immune system is one of the secondary complications. We don't know exactly why it happens. The immune system simply doesn't perform as well when the central nervous system is damaged."

Funded by a grant from TIRR Foundation's Mission Connect, Thrasher and Simpson will spend 12 months investigating the immune systems of 30 patients before and after functional electrical stimulation exercise. Using facilities at the UH Center for Neuromotor and Biomechanics Research in the Texas Medical Center and the UH Laboratory of Integrated Physiology, the study will examine 30 participants—10 with quadriplegia, 10 with paraplegia and 10 without spinal cord injuries. Simpson, an immunologist, will examine blood samples of study participants before and after exercise, investigating the quantity of immune cells.

"Although long-term stress is detrimental to our immune system, the everyday release of certain stress hormones, such as epinephrine, is important to help maintain normal functioning of the immune system and the continued circulation of our white blood cells," said Simpson. "Spinal cord injured patients are unable to activate the adrenal glands that are responsible for epinephrine release, which may be one reason why they have lowered immunity and greater incidences of infection."

Thrasher, a bio-engineer, will oversee participants' exercise.

"We're going to do an upper body exercise using an arm crank and a lower body exercise using functional electrical stimulation. A wheelchair will connect to a type of stationary bike. We will stimulate their muscles electrically," he said. Mission Connect is a collaborative neurotrauma research project focused on halting the progression of damage and restoring lost function in patients who have sustained a spinal cord injury, brain injury or stroke. Mission Connect brings to research the power of collaboration by uniting the region's brightest scientists and physicians in the effort to translate knowledge into a cure. The organization was created by The Institute for Rehabilitation and Research Foundation (TIRR Foundation) in 1997.

"Mission Connect is pleased to support the research of Drs. Thrasher and Simpson, and we look forward to learning of the progress we know they will achieve," said Cynthia Adkins, executive director of TIRR. "Spinal cord injury is a complicated and devastating injury, and we need highly gifted scientists to dedicate their efforts to solving the myriad of complex questions that remain unanswered."

The result of the 12-month study may be new drug therapies that stimulate the adrenal glands or new knowledge about the immune system that could benefit many populations.

Source: Health and human performance