Final answer:
Regulatory T cells (Treg) suppress the activity of autoreactive T cells and protect the body from autoimmune diseases.
Step-by-step explanation:
Regulatory T cells (Treg) play a crucial role in protecting the body from autoreactive T cells and preventing autoimmune diseases. These Treg cells suppress the activity of other T cells that mistakenly react against self antigens. By doing so, they help maintain tolerance and prevent autoimmune responses. Without regulatory T cells, autoreactive T cells could cause autoimmune diseases and other medical issues.