The Immune Tuner
Autoimmunity—when a person’s immune system attacks
parts of their own body—is the defining feature of many
common diseases, including celiac disease, MS, type 1
diabetes, and Hashimoto’s disease, to name a few. Why
does autoimmunity develop, and why is it seemingly on the
rise? Are we meant to have immune systems that harm our
bodies and brains in acts of friendly fire, or is this one more
aspect of our biology succumbing to the pitfalls of modern
life? To understand how our diets and lifestyles may
contribute to a confused immune system—and thus
autoimmunity—it helps to understand how this dynamic
system is “trained” throughout your life.
If you were to picture a cross section of a tunnel, you’d
get a pretty good sense of the anatomy of the large intestine.
The innermost tissue is the epithelium. This one-cell-layer-
thick barrier acts as the division between the interior of your
colon—known as the lumen—and your circulation. Because
its contents are not part of your body (similar to the air that
fills your lungs), the lumen is actually thought of by
scientists as being part of the host’s environment. In fact, the
gut is actually your largest interface with the environment—
much larger than your skin. If you were to remove your
entire digestive tube from your body, uncoil it, and sprawl it
out on the ground, it would take up the square footage of a
small studio apartment.
For this reason, the vast majority of our body’s immune
cells are primed to focus on what’s happening in our
digestive systems. Though this may seem counterintuitive,