It looks like Doc Shelly is missing a certain something.
Hey! Good going again!
So, you noticed that Doc Shelly never mentioned autoimmune diseases. Of course, he not only forgot to mention them, but also was wrong in saying that there are no threats left to the body after T-cells finish their work. We all know that autoimmune diseases, diseases in which the body's immune system turns on itself, are an extremely dangerous threat indeed. If the number of suppressor Ts in our system becomes exceedingly small, the immune system is hurting itself, and can cause these diseases.