Working out could boost the immune system by releasing ‘regulatory’ T cells – that fight heart disease, cancer, diabetes and dementia

The benefits of exercise may be partly due to the way being active boosts the immune system, scientists have suggested.

Researchers from Harvard Medical School found that exercise triggers the release of regulatory T cells, also known as Tregs, which increase the muscles’ ability to use energy as fuel and improve endurance.

These same cells are also known to play a role in countering inflammation linked to a range of health problems, including cardiovascular disease, cancer, diabetes and dementia.

Most previous studies of human performance have focused on the role of hormones released during exercise and their effects on various organs, but this new research is among the first to show how the immune system may play a role.

“The immune system, and the Treg arm in particular, has a broad impact on tissue health,” says Professor Diane Mathis of Harvard Medical School.

Although the findings relate to observations in laboratory mice, researchers say the study is an important step toward understanding molecular changes that occur during exercise that confer health benefits.

Exercise is known to temporarily damage muscles, causing a cascade of inflammatory responses. In the study, the team analyzed cells from the hind leg muscles of mice that walked on a treadmill just once, but also of mice that walked regularly. These were then compared to the muscles of sedentary mice.

The sets of both cells from the mice running on treadmills showed classic signs of inflammation and also had increased levels of Tregs in their muscles – which reduced exercise-induced inflammation. Neither change was observed in the sedentary mice.

However, other Treg benefits induced by exercise – such as improved muscle performance – were only observed in regular treadmill runners, consistent with established findings in humans that regular activity is required to achieve gains over time.

The Harvard experts also suggest that another role of Tregs is to counteract the harmful effects of interferons – proteins released as part of the body’s inflammatory response.

“With exercise we have a natural way to boost the body’s immune responses to reduce inflammation,” adds Prof. Mathis. ‘It is possible that exercise also stimulates Treg activity elsewhere in the body.’