Skin acts as a barrier between invaders (pathogens) and your body. Digestive system defense has enzymes. The enzymes in your stomach, pancreas, and liver help destroy pathogens. The circulatory system contains immune cells called lymphocytes, which protect the body against antigens (viruses, bacteria, etc. ) that invade the body. The respiratory system is a layered defense mechanism which relies on components of both the innate and adaptive immune systems to protect the lungs and the rest of the respiratory tract against inhaled microorganisms. The body’s innate immune system (nervous system), its first line of defense, recognizes infectious microorganisms such as bacteria, and initiates a generalized short-acting response while summoning the body’s adaptive immune cells to mount a sustained and targeted attack.
