Answer:
the innate immune system
Step-by-step explanation:
The most effective first line of defense against cancer is the innate immune system. The innate immune system is composed of cells such as natural killer cells, dendritic cells, polymorphonuclear cells, mast cells, and macrophages, which are the first-line effectors to damaged cells and cancer cells. These cells quickly respond to foreign cells to fight infection, battle a virus, or defend the body against bacteria. The immune system is the body's natural defense against cancer, and the innate immune system is the first line of defense against cancer.