A watchdog that doesn't bark at a stranger is a bad guard. In people with type 2 diabetes, the guard cells known as T cells behave the same way: they stop recognizing the enemy. These cells are supposed to find sick cells and kill them, but in diabetes they lose their sensors, special proteins on the surface that help them sniff out danger.
Scientists have figured out that the molecule TGFβ1 is to blame. In diabetes there is too much of it in the blood, and it acts like a sleeping pill: it makes the cell hide its sensors inside itself, where they don't work. As a result, T cells can't find the enemy and get stuck in the spleen, like a dog that won't leave its kennel.
People used to think that immunity in diabetes simply ages faster. Now it's clear that the disease doesn't speed up aging but breaks the recognition system itself: the dog stays strong, but blind and deaf. Whether it can be woken up is a question scientists are only beginning to answer.
In patients with diabetes, memory T cells have shorter telomeres but more telomerase (TERT) than those of healthy peers. This looks paradoxical: the cell tries to compensate for wear and tear but cannot stop aging.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.