How exercise might affect immunity to reduce cancer risk

So recently, a group of scientists from the Karolinska Institute in Stockholm and other institutions began to wonder about white blood cells. As part of the immune system, white blood cells play a key role in our defense against cancer by noting, navigating and often annihilating malignant cells. Researchers have known for some time that different types of immune cells tend to target different types of cancer. But little is known about whether and how exercise affects any of these immune cells, and whether these changes might somehow contribute to the mitigating effects of cancer.

Now, for the new study, which was published in October in eLife, Swedish scientists decided to find out more by inoculating mice with different types of cancer cells and letting some rodents run around, while others stayed behind. sedentary. After several weeks, the researchers found that some runners showed little sign of tumor growth. More intriguingly, most of these active mice had been inoculated with cancer cells known to be particularly vulnerable to a specific type of immune cell, called CD8 + T cells, which tend, primarily, to fight certain forms of breast cancer and other solids. tumors.

Perhaps, according to the researchers, exercise had particular effects on these immune cells.

To find out, they then chemically blocked the action of these T cells in the animals with tumor cells and let them run. After several weeks and despite their activity, animals without functioning CD8 + T cells showed significant tumor growth, suggesting that CD8 + cells, when working, must be a key part of how exercise helps. to ward off certain cancers.

For further confirmation, the scientists then isolated CD8 + T cells from animals that ran and those that did not. They then injected either type of T cell into sedentary, cancer-prone animals. Animals that received immune cells from runners then fought tumors significantly better than animals that received immune cells from inactive mice.

The results surprised and excited the researchers, says Randall Johnson, professor of molecular physiology with two appointments at the University of Cambridge in England and the Karolinska Institute, which oversaw the new study. They appeared to demonstrate “that the effect of exercise on T cells is intrinsic to the cells themselves and is persistent,” he says.