The immune system also fights and assists the fight against mutations. Also other major systems in the organism help fight off the bad effects of mutations, such as the renal and lymphatic systems acting to remove toxins, and other systems provide the resources the immumne system needs-- such as the bone struture providing a housing for the bone marrow which creates the immune agents for delivery and patroling via the blood.
As I stated, as much as my pencil eraser fights and assists the fight against federal corruption.