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Comment by biotechbio | Hacker News Reader

bioscience phd student. Why is this interesting?

Tl;dr from the article, they used flow cytometry to quantify different cell populations in the blood, and noted that the proportion of CD8+ T cells (cytotoxic, the kind of immune cells that recognize and kill cancer cells, among other things) increases after exercise and returns to baseline 30 min later.

Claiming that this supports the idea that cancer patients could benefit* from exercise is a pretty big overstep of scientific inference.

* = in the immune response to their cancer

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Medical doctor. This is exactly what I thought.

There's simply not enough here to say if it's just an interesting artefact of exercise or an actual helpful response. It may be a useful starting point for further studies, but the comment section is frightening in how quickly people are jumping on this to confirm their biases on health and disease.

If we were to extrapolate from this logic, we would wrongly conclude that people with autoimmune diseases should never exercise.

If they return to baseline in 30 minutes, was there even an increase to begin with? What is the mean lifetime of those cytotoxic cells, and would one expect such a decay in so short a time?

I understand that it is a very dynamic system but 30 minutes seems very short to me. So is the return a die-off or where do they go?

The lifespan of T cells varies from months to years (memory T cells). T cell development begins in the bone marrow and continues in the lymphatic tissue and periphery. During their lifespan, these cells circulate in the body and migrate based on chemical gradients.

What happens when you exercise? Blood pressure increases, blood vessels dilate. I honestly would not be surprised if what these authors observed was just existing T cells in capillary beds being kicked up into circulation, only to adhere and begin to intravasate a couple minutes later.

Excellent explanation, thanks.

That seems to translate well to my layman intuition. Would there actually be a health benefit with respect to cancer (or pathogenic disease) from this "T cell migration"? Is there a sense in which migration of T cells spread information to different parts of the body or is this just not how it works?

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