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Innate and Adaptive Immunity

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  • The vertebrate, including human, immune system is a complex multilayered system for defending against external and internal threats to the integrity of the body. The system can be divided into two types of defense systems: the innate immune system, which is nonspecific toward a particular kind of pathogen, and the adaptive immune system, which is specific (Figure). Innate immunity is not caused by an infection or vaccination and depends initially on physical and chemical barriers that work on all pathogens, sometimes called the first line of defense. The second line of defense of the innate system includes chemical signals that produce inflammation and fever responses as well as mobilizing protective cells and other chemical defenses. The adaptive immune system mounts a highly specific response to substances and organisms that do not belong in the body. The adaptive system takes longer to respond and has a memory system that allows it to respond with greater intensity should the body reencounter a pathogen even years later.

     Table shows vertebrate immunity, with 2 columns for innate and adaptive immune system characteristics. The innate immune system if further divided into physical barriers and internal defenses. Under physical barriers are: skin, hairs, cilia, mucus membranes, mucus and chemical secretions, digestive enzymes in mouth, and stomach acid. Under internal defenses are: inflammatory response, complement proteins, phagocytic cells, and natural killer (NK) cells. In the adaptive immune system column are: antibodies and the humoral immune response, cell-mediated immune response, and memory response.There are two main parts to the vertebrate immune system. The innate immune system, which is made up of physical barriers and internal defenses, responds to all pathogens. The adaptive immune system is highly specific.

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