worms for autoimmune conditions?

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The Wild Life Of Our Bodies: Predators, Parasites, and Partners that Shape Who We Are Today, Rob Dunn, HarperCollins, 2011.



[page 40:]

' . . . "Different" is how one immunologist characterized the immune system of people in developed countries. This is the language of uncertainty. No one knows quite what happens when we take our parasites away. Take all of our worms away entirely, and we seem to stand a greater chance of getting sick. Put some of them back and we get better, much of the time anyway [emphasis added]. . . '



[page 41:]

' . . . The body is a country with two immunological armed forces. One fights one kind of foe, viruses and bacteria; the other deals with another kind of foe, nematodes and other larger parasites. . . '



[page 42-43:]

' . . . It turns out we had completely missed a key component of the immune system, the peacekeepers. When a parasite is ensconced and initial attempts to expel it are unsuccessful, what should the body do? It could fight forever. In some cases this does happen and when it does, the disease and the problems caused by the body's immune response almost inevitably outweigh the trouble caused by the worm itself. In this context, the body may be better off giving in to the reality that the worm is present and learning to tolerate it. The answer appears to be, again and again, that if the parasite survives initially, the body learns to tolerate it. A team of peacekeeper cells calls off the antiparasite armed forces. The peacekeepers balance the response. They reserve the body's energy to fight another day against a more beatable or virulent foe.

'What Weinstock, Rook,* and others think is that these newly discovered peacekeepers are, in a way, our historical solution, but also our modern problem. The peacekeepers, they imagine, get produced only when there is peace to keep. When there are no ensconced parasites, particularly early in development [emphasis added], the peacekeepers dither and wither. But the forces remain strong, and so without being otherwise occupied, they attack whatever seems foreign. They can sometimes be so eager to win that they fight whatever they come across. The body's own bits and pieces begin to seem threatening. The peacekeepers that might otherwise call these increasingly indiscriminate forces back, do not. They are too weak. Unchecked, our immune system battles our bodies without end. It battles our bodies until we are sick and then sicker. Boils erupt on our skin. Our intestines become inflamed. It battles our bodies until there are no winners.

'Weinstock thinks that when he introduced worms into patients, their bodies began to produce peacekeepers, which kept the peace by stopping the immune system from attacking the worms. Of course, just like the cheetahs that pursue pronghorn, hookworms can have costs, the most common of which is the loss of blood in severe infections and consequent anemia. But on average the costs appear minimal, both in a general sense and relative to the costs of fighting the worm forever. If the worm is well ensconced and the body continues to fight it (or them), the body wastes energy. And so it may be that the peacekeepers provides a mechanism for the gut to admit local defeat and at the same time prevent the immune system from a prolonged attack on the gut, whether a worm is present or in other situations. The peacekeepers keep the peace. The worms, in their way, trigger that peace. Maybe [emphasis added].

'A second possibility also exists and this possibility (which is not really exclusive of the first) . . . '


*Joel Weinstock, Graham Rook

[pages 43-44:]

'A second possibility also exists and this possibility (which is not really exclusive of the first) is my own favorite. It has long been known that worms in our guts can produce compounds that suppress the immune system, compounds that, in essence, signal, “Hey, it’s cool in here—no need to attack.” They do so by mimicking some of the body’s own compounds. Many different worms produce these compounds. It may be that our bodies evolved to depend on at least low levels of such worm-produced compounds. Here I do not mean that our bodies needed them, at least not originally, so much as that they could count on their always being there. Perhaps our bodies produce more of an immune response than is necessary because they are, in a way, “assuming” that some of their response will be dulled by the worms. No one can show that such a phenomenon is occurring, not yet, but it seems plausible.

'In the meantime, the broader reality is that our immune systems appear to have evolved in such a way as to function “normally” only when worms are present. Scientist other than Weinstock have called this phenomenon the hygiene hypothesis, where the idea is that clean living is bad for us because the functioning of our immune systems needs the “dirty” realities of worms and maybe even a particular microbe or two. . . '


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