Regulatory T cells play an important role in the immunity process: they help the body distinguish between harmful intruders and the body itself. They work by moderating the immune response, recognizing what tissue is legitimately part of the body and preventing the effector T cells, the cells that actually carry out infection-fighting functions, from attacking those organs. The regulatory T cells are also responsible for dialing down the immune response once an invading microbe has been successfully vanquished.
When the regulatory T cells fail, the resulting condition in what is known as an autoimmune disease. These conditions occur when the immune system attacks a part of the body as though it were an infection. Common autoimmune conditions include allergies, multiple sclerosis, lupus, vitiligo, Sjögren’s syndrome, rheumatoid arthritis, type 1 diabetes, Crohn’s disease, celiac, and myasthenia gravis. These conditions mostly strike women, often have a strong genetic component, and tend to result in inflammation in the affected area. Treatment often focuses on the symptoms—the inflammation—or involves deliberately reducing immune activity, though building on the observation that regions with more parasitic infection have a lower incidence of autoimmunity, carefully controlled introduction to the body of certain types of parasites.
Now researchers are starting to develop another treatment using various types of T cells. It turns out that T cells can be taught to tell the difference between valid targets and healthy tissue in the lab. The researchers developed a technique to harvest undifferentiated, or naïve, T cells from the blood, treat them with progesterone to turn them into an inflammation-suppressing type of cell, and then reintroduce them. Unlike the immune suppression treatments currently used, this procedure has no effect on the immune system in parts of the body where autoimmunity isn’t occurring. Rather than a general dialing back, it’s a specific and targeted reduction. This precision could make it possible for the treatment to be much more aggressive.