Al Stahler: How the human body defends itself against pathogens |

Al Stahler: How the human body defends itself against pathogens

Al Stahler

A new disease that strikes the young and middle-aged — but not so much the older folks — is not really new. The pattern tells us that it had swept through before, when today’s old folks were young themselves, making their immune systems ready to fight off the disease, next time ‘round.

COVID-19, however, strikes all ages, old folks hardest of all. COVID-19 is, indeed, new. We need to prepare our immune systems to fight it.

Genes are instructions. Genes tell our bodies how to live, how to grow, how to make repairs. Everything alive has genes.

Viruses have genes, but whether viruses are alive is a matter of debate. While our genes tell our bodies how to live, viruses do not, themselves, have bodies. Once inside us, viral genes instruct our bodies what to do, and what they tell us to do is to make more viruses, which we then spread, to family, friends and neighbors.

Scrape up a bit of that film that’s been growing in the corner of the shower stall, and put it under the microscope. What you see are tiny, single-cell organisms: bacteria. Each cell can do everything needed to stay alive: eat, drink and make more bacteria.

Our own bodies are made of gazillions of cells. Different cells do different things: we’ve got blood cells, nerve cells, muscle cells, skin cells.

Place a finger on your breastbone, high in your chest. Behind your breast bone lies your thymus. The thymus is a training center for the immune system’s T-cells — “T” for thymus. These T-cells, like other cells, are named for their jobs.

They’re killer T-cells.

Killer T-cells roam our bodies, and kill — eat — bugs that mean us harm. Killer T-cells are a part of the immune system that gives us a fighting chance in a world of nasties.

Now put you hand over your heart, and drop it straight down, half-way to the level of your belly-button. You’ve found your spleen. It’s here that another part of the offense — “natural killer cells” — are produced.

Our immune system involves much more than these; it is assembled, not in any one part of the body, but in many.

Not only is the immune system not assembled in any one place, it’s not all made at the same time. Some parts are made only while we’re awake; other parts, only as we sleep. If we cheat on sleep, we weaken some of our immune system.

Given the millions of years that humans have lived on Earth, supermarkets are a pretty recent invention. For most of our history, we’ve eaten what we’ve hunted and gathered … which involves a lot of moving around.

Our immune system seems to know whether we’ve been moving … it seems to ask, “Is my body hunting? Is my body gathering? Is my body moving?”

If not, the immune system seems to say, perhaps the food my body is consuming would be better eaten by family and friends, perhaps protecting this body from bugs is not worth the effort.

Or perhaps (very possibly), something else is going on. But, for whatever reason, if the immune system senses that its body is not moving much, it slows down … way down.

You don’t have to do push-ups, or sit-ups, you don’t have to run a marathon. A great form of movement is walking, several times a day, every day. You can invite your neighbors to join you, so long as you keep the social distance thing going.

If you have to stay indoors, if the foothills are slammed with shelter in place, you can jog in place — maybe even dance — try to make it fun.

Whatever you do — and I say this to myself, as much as to anyone — if you want a healthy immune system, get off your butt! Do it now, do it again, later today, do it again tomorrow.

That said, the ecology of disease is super-complex. Let’s not assign blame when someone gets sick.

Interestingly, it’s been found that moving your body is also an anti-depressant, an anti-anxietal — it even makes it easier to fall asleep.

Looking up

Skies should clear, at least part of the time, this week. Planet Venus will shine bright in the west, and the first quarter moon in the south, after sunset.

On Earth, mountains are washed to the sea, but on the airless moon, mountains can last. Some of the rocks collected by Apollo astronauts in the lunar highlands — the bright parts of the “Man in the Moon” — are older than any rocks found on Earth — over 4 billion years old.

Rocks from the dark parts of the Man in the Moon” — the lunar lowlands — are younger — not quite 4 billion years old. These rocks formed when lava (dark basalt, the same rock that erupts in Hawaii), burbled to the surface after huge asteroids, dozens of miles across, slammed into the moon (and, no doubt, into Earth), excavating huge basins. This was a violent time in our part of the solar system.

This was also a significant time in the history of life. Prior to roughly 4 billion years ago, there was no life on Earth — just rock, water and air.

Darwin hypothesized that life evolved, long ago, in a “warm little pond.” But, given the evidence we see on the moon — evidence for tremendous violence, right around the time life came to be — it’s now thought more likely that the first life evolved deep beneath the sea.

Al Stahler enjoys sharing science and nature with friends and neighbors on KVMR-FM, and can be reached at

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