Self antigens are ...

• A. foreign to the body
• B. triggers autoimmune disease in all individuals
• C. antigens that the immune system tolerates in the host
• D. only trigger immunity when vaccines are given

Answer: (C)

The immune system is trained to tolerate self antigens, meaning the body's own components are normally ignored and not attacked. This tolerance is built through mechanisms like central tolerance, where self-reactive T and B cells are deleted or edited during development, and peripheral tolerance, where regulatory T cells and other checks prevent activation of self-reactive cells. Because of this, self antigens are considered something the immune system tolerates in the host rather than targets for immunity.

They are not foreign to the body, so they don’t automatically provoke an immune response. Autoimmune diseases can occur if tolerance fails, but that doesn’t happen in everyone. Vaccines work by presenting non-self antigens to stimulate protective immunity, not by triggering responses to the body's own components.