It keeps you alive … until it doesn't

kw: book reviews, nonfiction, medicine, immune system

Once we didn't know anything about immunity. People died in droves from simple infections and diseases. Plague could ravage the earth, and nobody knew why. Then, no more than a couple of centuries ago, doctors began to recognize something in our bodies that fought invasions, infections, and diseases. By the Twentieth Century a number of special kinds of cells were known, and their role in destroying bacteria and viruses was being studied. When I was young, they were just called "white blood cells" and the main difference between a small number of known cell types was the number of nuclei and their size. That soon began to change.

Around fifty years ago our image of immune cells was like Rambo: Find enemy, blow enemy to bits. Over time, and with huge amounts of research, nuances were discovered. Chemical probing became more sophisticated, and dozens of cell types could be discerned; at first just macrophages ("big eaters") and the B and T "killer cells" were known, but later many more. Now some cells are known that slow down the killers, so the whole system can strike a balance between "scorched earth" and "admit all comers".

An Elegant Defense: The Extraordinary New Science of The Immune System – A Tale in Four Lives, by Matt Richtel, presents the history and development of immune system science in a comprehensive way, and that's just his introduction (about 35% of the book). Then he tells four life stories, one of his boyhood friend Jason Greenstein and his dramatic battle with Hodgkin's lymphoma; another of Bob Hoff, the poster child of "elite controllers", whose immune system keeps AIDS at bay; and two women, Linda Bowman and Merredith (last name withheld), whose immune systems—not so much like Rambo but more like the bodyguards of Indian Prime Minister Indira Ghandi, who assassinated her—turned against them.

We think of organs as rather solid things, like stomach and heart, made of cells that cling to one another as definite tissues. It is amazing to realize that a few pounds of our substance consists of free-roaming cells, that can look a lot like amoebae, and which move freely between our blood and any tissue in the body. However, the brain has its own immune system; the blood-brain barrier is too tight for the immune cells from the rest of the body to penetrate.

Twenty years ago, after I was operated on for colon cancer, I asked my oncologist how chemotherapy would affect my immune system. He said, "The cancer itself is evidence that your immune system wasn't quite up to the task. It will be weakened some more by the chemo, but will recover. Later on we'll instruct you how to keep it healthy." His advice must have worked; I'm still here.

A few years later a pre-teen girl in our church developed juvenile Lupus. Her immune system was overdoing things and attacking her body, not continually but in periodic episodes. With some reading and asking questions of doctors we found that the main trigger of her attacks was UV light in sunlight. Then I remembered a portion of Brave New World by Aldous Huxley: certain people were given jobs underground or in the dark, because they suffered from Lupus if they were exposed to the sun. We put special UV-blocking film on the windows of the church's meeting place, her family had their cars' windows tinted, and she got special UV-blocking clothing. Within about ten years she recovered from it, as often happens with juvenile Lupus. She needs less vitamin D now. Her skin, which was once the whitest I've ever seen, can tan a little, but she's still careful not to get too much sun.

I don't think it wise to summarize the sturm und drang of the ordeals endured by the four persons. There is just too much detail. The key message for me is that the immune system isn't just a killer organ. It is a balance organ.

Imagine that our immune system were infallible in determining what is Self and what is Other, and totally effective in eliminating Other. We would certainly be germ-free. However, the expense would likely be more than the body could afford, keeping a horde of hunter-killer entities supplied. One doctor described such an outcome as a "ten-foot pimple". Perhaps one could get used to it, but I'd rather not try!

In such a case, we would have no microbiota. But we do have our "internal flora" and I am not sure we could live without them. Some of the bacteria in our gut produce vitamin B-12. Others produce other nutrients and life-support chemicals. It is like the animal body (not just human!) is evolved to "steal" a lot of capabilities so it doesn't need to develop them itself. It is an advanced version of my practice of hiring contractors (like some concrete workers who are outside repairing my sidewalk as I write). There are lots of things I don't know how to do; I could learn, but it saves time when I can afford to hire work done.

Thus, the immune system has reached accommodation with thousands of species of bacteria and other microbes (I'm not sure what-all) to run our bodies more efficiently. Many of those species guard against pathogens and effectively form an extended part of our immune system.

There is a sad note at the end of the book when the author discusses death. Medicine isn't really about life-saving so much as life-extending and health-extending. We would like to live forever. Before there was modern medicine, or even Herodotus-level medicine, a few people would live more than 100 years, sometimes approaching 120 years. In fact, someone who is more than 100 years old today lived a number of years in a world without antibiotics or the public health measures that keep cholera and other scourges at bay. The only person in the modern era who lived 120 years or more was Jeanne Louise Calment, who lived just about 122½ years. She flirted with Van Gogh as a teen!

To put it bluntly, our amazing immune system, honed by four billion years of natural selection, usually does an excellent job keeping us alive and usually healthy until we have had time to reproduce and raise our children. Then it backs off, and backs off… For some, their natural life span is 60-70 years. For others it can be decades longer. The limit seems to be 120-ish, with no more than one or two persons per generation exceeding 110 years. Medical science has increased the average life span without making a dent in the limiting life span. Along the way, for most of us, our health span has increased dramatically compared to our grandparents and before. A great deal more must be learned if we are to modify our immune system's "program of senescence".

This book deserves a permanent place on our shelves. The author's summary of immune system science quite amazes me. I'll have to re-read some parts to get comfortable with the details. Keeping a body alive is no single-shot task; it demands an army that has dozens of specialized functions, including negotiators. Amazing!