The body depends on the immune(免疫) system to fight infections the same way it depends on the digestive system(消化系统) to digest food The immune system also keeps some types of cancer from taking over the bod With no immune system(免疫系统),a person would die from a simple infection such as a cold or flu(流感)The body depends on the immune (免疫) system to fight infections the same way it depends on the digestive system (消化系统) to digest food. The immune system also keeps some types of cancer from taking over the body. With no immune system (免疫系统), a person would die from a simple infection such as a cold or flu (流感)