Immune System

The immune system is made up of tissues, cells, and organs that help your body fight off illness and disease. Your skin prevents pathogens, which are germs or chemicals that make you sick, from entering your body. Mucus in your nose traps many of the pathogens that you inhale from entering your body and bloodstream. Stomach acids kill bacteria that live on the food you eat. White blood cells, or leukocytes, patrol your bloodstream looking for the germs.