Not all immune cells are equal
White blood cells of the immune system fight cancer, bacteria, and viruses. However, not all white blood cells destroy cancer cells and some even promote cancer growth such as regulatory T cells and myeloid-derived suppressor cells. When it comes to fighting cancer the most important cancer cells are cytotoxic T cells and natural killer cells.
“The balance of different types of white blood cells determines whether the immune system works to destroy cancer or to support it. If there are more cancer-destroying cells than cancer-promoting cells in the tumor area, the body is more capable of fighting cancer,” says lead author, Doctoral Researcher Tiia Koivula from the University of Turku, Finland.
The study
For this study, 20 breast cancer patients who had not started cancer treatments pedaled a bicycle ergometer for 30 minutes at the resistance of their choosing. Blood samples were taken from the participants before, during, and after the exercise session to calculate the amount of different types of white blood cells at the different collection times.
What they found
The analysis revealed that during exercise, the amount of several different white blood cell types increased in the bloodstream. While the number of cancer-destroying cytotoxic T cells and natural killer cells increased the most, the number of cancer-promoting regulatory T cells and myeloid-derived suppressor cells did not change.
Examining the proportions of different white blood cell types relative to the total white blood cell count revealed that the proportion of natural killer cells increased significantly, while the proportion of myeloid-derived suppressor cells decreased.
Further analysis of whether different types of breast cancer affect the exercise responses of white blood cells revealed that the larger the tumor, the less the number of natural killer cells increased, and if the breast cancer was estrogen and/or progesterone receptor-positive, the number of cytotoxic T cells increased less than in hormone receptor-negative cancers.
More research needed
“We found that during the exercise, the number and proportion of cancer-destroying cells increases in the bloodstream, while the proportion of cancer-promoting cells either stays the same or decreases. However, it is still unclear whether these changes seen in the bloodstream also lead to changes in the white blood cell counts in tumor area,” says Koivula.
“In this study, it was seen that the number of almost all white blood cell types decreased back to resting values one hour after the exercise. With the current knowledge, we cannot say where the white blood cells go after the exercise, but in preclinical studies, cancer-destroying cells have been seen to migrate into the tumor area.”
“In our previous study, we found small indications that the type of breast cancer might affect the effects of exercise on white blood cells, which is why we wanted to examine it further. However, the correlations we found were not very strong and therefore, no decisive conclusions can be drawn from the results. According to current knowledge, it is beneficial for all cancer patients to exercise, and our recent study supports this notion,” Koivula encourages.
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