A collaborative research initiative at the NC Research Campus looks into the effects of exercise on NK cells, uncovering new evidence about the link between physical activity and immunity.
In 1990, David Nieman, DrPH, discovered that marathon runners experienced higher levels of upper respiratory infections after competing. He also found out one reason why. The levels of natural killer immune cells (NK cells) initially increased only to flounder after intense endurance running, leaving the athlete immunosuppressed.
Twenty-five years later, Nieman, who is the director of the Appalachian State University Human Performance Laboratory at the NC Research Campus in Kannapolis, NC, launched a new study into the effects of exercise on NK cells, which are a type of lymphocyte that act as a “first responder” directly targeting virally-infected and abnormally-growing cells.
Partnering with Renaud Warin, PhD, with the North Carolina Agricultural and Technical University (NC A&T) Center for Excellence in Post-harvest Technologies also at the NC Research Campus, Nieman led a pilot study that revealed how NK cells bounce back at higher than pre-exercise levels in less than 24 hours after the initial window of suppression.
NK Cells: “Navy Seals” of the Immune System
“When you exercise, NK cells are the most responsive of all immune cells,” Nieman said. “Exercise gets the blood going and sends NK cells out like they are ‘Navy Seals’ being told to go out, start circulating, and look for the enemy.”
In Nieman’s 1990 study, he and his research team were not able to isolate NK cells, which are a relatively small proportion of the immune cells. Instead, the lymphocytes of marathon runners who had exercised in the lab for three hours were mixed with cultures of cancer cells at various time points post-exercise to observe their potential to kill harmful cells.
In the 2015 pilot study, Warin applied a magnetic-based separation technology to produce a pure population of NK cells from blood samples taken from four participants before and after running at high intensity for two and a half hours in the lab. The results showed that NK cells specifically were not killing at full capacity beginning four hours after exercising, validating the type of immune suppression Nieman identified in 1990. Blood samples taken the next morning showed NK cells bouncing back at above normal levels, indicating that additional immune protection is occurring less than 24 hours after an intense period of exercise.
“The experimental flow-through methodology is fast, reliable, and not subject to user error,” said Warin, who is a nutritional immunologist with extensive experience studying NK cells and a cyclist who has participated in many of Nieman’s studies. “By using it, we’ve been able to develop the premise going forward that if you keep exercising, NK cells may learn to be overactive all the time.”
Although their ongoing research examines the immunological effect on endurance runners, there is no reason why the average person who exercises on a regular basis will not also experience immunological benefits. Several studies show that walking five days a week for 45 minutes per day results in a 40 to 50 percent reduction in illness.
Both Nieman and Warin believe that applying the methodology from the pilot study on larger population of athletes will lead them to discover the reason why NK cells bounce back so well 24 hours after intense exercise. They are also exploring ways to close the window of immune suppression potentially through the ingestion of phytochemicals and nutrients in fruits and vegetables to increase the exercise-induced effects of NK cells.
In all, this collaborative partnership will improve scientific understanding of how NK cells respond to varying exercise doses, and nutritional countermeasures to the transient decrease in NK cell function after heavy exertion.
By: Kara Marker, NCRC Marketing