A Good Holobiont has a Good Immune System. Managing your Microbial Environment

 

An incredible book by Philipp Dettmer: an ambitious attempt to tell the whole story of the human immune system in an understandable form even for the non-specialist. The result is a 345-page tome, lavishly illustrated, and written in an entertaining style. Remarkably well done, but not easy to digest nevertheless. I went through the whole thing once, but I need to restart from the beginning and reread it again. And, probably, I'll need a third pass. Afterward, I may be able to say that I know just a little bit about how the immune system works. 

And think that this is just an introduction that neglects or just mentions several important details. For instance, it mostly skips the role of the microbiome. But that must be hugely important: after all, human beings are holobionts. We can't survive without our microbiome, and it is likely that the huge numbers of small critters that populate our body play a fundamental role in managing the microbial system "holobiont-style." It means that the immune system is not a sort of Nazi militia that shoots down everything it doesn't recognize and doesn't like. It must be able to recognize those parts of the microbiome which are helpful and those which are not. And note that, in some cases, the same species of microbes can play the role of pathogen or symbiont, depending on the general conditions of the rest of the system. That's how good holobionts behave: they adapt to each other. We need to be colonized by microbes in order to survive. It is just a question of being colonized by the good ones. And it is the job of the immune system to ensure that it happens!

Amazing, as I said. It gives you a glimpse of the immense complexity of just a section for the even more immense complexity of the ecosystem -- that some call "Gaia." The goddess gave every one of us a complete defense and management system that kept our ancestors alive for the past 400 million years or so as multicellular organisms, and also a few billion years as single-cell organisms. If we are here, it means that the immune system of our ancestors worked well enough to interact with, and protect them from, the zillions and zillions of microscopic creatures that we eat, inhale, or come in contact with one way or another. 

But, wait.... aren't we supposed to be much smarter than Gaia, that poor old lady? We are so smart that we discovered that we can do better than just relying on that old stuff that uses billions of antibodies, t-cells, macrophages, and more. You know, those squishy things that evolved over a few billion years, what are they for? Instead, just a piece of cloth placed onto your mouth and nose, and -- voilà -- NOW you are safe!