Scientists focusing on how exercise raises immunity

An increasing number of doctors and other health experts have been encouraging older adults to rise from their recliners and go for a walk, a bike ride, a swim, or engage in just about any other form of physical activity as a defense against the potentially harmful health consequences of a sedentary lifestyle.

“Exercise is touted as a panacea for older adults,” said Jeffrey Woods, a kinesiology professor at the University of Illinois at Urbana-Champaign, who noted that fitness programs are routinely recommended for people with various health problems — from diabetes to heart disease.

Health experts generally recognize that this population benefits from physical fitness, he said. What they don’t know is why exercise appears to have certain preventive and restorative health effects. Also unknown is what — if any — relationship exists between exercise and immune functioning.

“Despite the numerous benefits of exercise — for example, improving cardiovascular and muscular fitness — we know very little about how exercise affects the immune systems of older adults,” Woods said. “Good, bad or indifferent, this information could have important public health consequences for our aging population.” For that reason, Woods and colleagues in the university’s kinesiology department are conducting research that seeks to establish the link between exercise training and immune function. The field, he said, is still in its infancy, with Illinois researchers among those who are defining it.

“Our laboratory is using both animal and human models to address the extent to which exercise affects immune functioning and susceptibility to infectious disease in older populations,” Woods said. “We have obtained some exciting preliminary data in mice that suggest that moderate exercise or training may boost some immune function measures and reduce mortality caused by influenza. While we don’t have corollary evidence yet in people, we are in the midst of conducting a large clinical exercise trial in older adults, funded by the National Institute on Aging, that will provide definitive evidence as to whether moderate exercise training influences immune function.”

In the meantime, results of one study conducted in Woods’ lab, published in the current online edition of the journal Brain, Behavior and Immunity, indicates that exercise training increases the ratio of naïve T cells to memory T cells in the spleens of older mice. The finding is potentially significant, he said, because, on this measure, “we turn old mice into young mice.” When people and animals age, he explained, the thymus, which produces naïve T lymphocytes, shrinks, thus producing fewer naïve cells. “This is one reason that older people/animals have trouble responding to new environmental pathogens.”

And with the recent appearance of so many new environmental pathogens — from West Nile Virus to SARS and monkeypox — Woods said the ability to boost the immune systems of the elderly, who are among the populations most at risk from infection, is a worthy goal.