Innate vs. Adaptive ImmunityThe immune system is typically divided into two categories--innate and adaptive--although these distinctions are not mutually exclusive. Show
Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body. These mechanisms include physical barriers such as skin, chemicals in the blood, and immune system cells that attack foreign cells in the body. The innate immune response is activated by chemical properties of the antigen. Adaptive immunityAdaptive immunity refers to antigen-specific immune response. The adaptive immune response is more complex than the innate. The antigen first must be processed and recognized. Once an antigen has been recognized, the adaptive immune system creates an army of immune cells specifically designed to attack that antigen. Adaptive immunity also includes a "memory" that makes future responses against a specific antigen more efficient.
The Biology Project The University of Arizona May 24, 2000 Contact the Development Team http://www.biology.arizona.edu Innate immunity and adaptive immunity are the two categories of the immune system of animals. The immune system consists of a collection of molecules, cells, and tissues, which protect the body from various pathogens and toxins. Innate immunity is always present in the body while adaptive immunity only occurs in response to exposure to an external factor. The main difference between innate immunity and adaptive immunity is that innate immunity generates a non-specific immune response against the pathogen whereas adaptive immunity generates a specific immune response against a particular pathogen. Key Areas Covered1.
What is Innate Immunity Key Terms: Adaptive Immunity, Antibody, Antigen, Cell-Mediated Immunity, Humoral Immunity, Innate Immunity, Phagocytes, Physical and Chemical Barriers What is Innate ImmunityInnate immunity refers to a naturally occurring immunity by the genetic constituents and the physiology of a person. Innate immunity is present at birth, and it lasts throughout the lifetime. Prior exposure to pathogens is not required by innate immunity. The removal of pathogens by the innate immunity occurs either internally or externally. The external defense serves as the first line defense against pathogens, and it is achieved by the physical and chemical barriers. Saliva, tears, skin, mucus linings, stomach acid, and some of the bacteria in the gut serve as barriers, preventing the entering of pathogens to the tissues of the body. The second line defense is the internal defense mechanisms of the innate immunity. Various types of phagocytes serve as internal barriers, preventing the growth and reproduction of pathogens inside the tissues. Natural killer cells, macrophages, monocytes, neutrophils, mast cells, and dendritic cells are examples of cells involved in the innate immunity. These cells destroy pathogens by phagocytosis. They also activate the complement system of the body as well as adaptive immunity. The cells involved in innate immunity are shown in figure 1. Figure 1: Cells of Innate Immunity Both external and internal mechanisms of the innate immunity generate non-specific immune responses against the pathogens. What is Adaptive ImmunityAdaptive immunity refers to an acquired immunity which is mediated by T cells and B cells and is characterized by an immunological memory. It serves as the third line defense of the body. The activation of the adaptive immunity occurs in response to an overcoming of the second line barriers by a particular pathogen. Cell-mediated immunity and humoral immunity are the two types of adaptive immunity. Cell-mediated immunity is mediated by cytotoxic T cells, which induce the cell death of infected cells. The helper T cells are the other type of T cells that activate B cells to produce antibodies. The production of specific antibodies against a particular pathogen occurs in humoral immunity. The corporation between first line, second line, and third line defenses are shown in figure 2. Figure 2: First Line, Second Line, and Third Line Defenses Due to its ability to respond to a large number of pathogens, adaptive immunity is considered as possessing a higher diversity. Once it responds to a particular pathogen, the adaptive immune system keeps the memory of the pathogen, developing a strong immune response in the second time exposure. Similarities Between Innate and Adaptive Immunity
Difference Between Innate and Adaptive ImmunityDefinitionInnate Immunity:Innate immunity refers to a naturally occurring immunity by the genetic constituents and the physiology of a person. Adaptive Immunity: Adaptive immunity refers to an acquired immunity, which is mediated by T cells and B cells and is characterized by an immunological memory. Alternative NamesInnate Immunity: Innate immunity is known as natural immunity. Adaptive Immunity: Adaptive immunity is known as acquired immunity. SpecificityInnate Immunity:Innate immunity generates a non-specific immune response. Adaptive Immunity: Adaptive immunity generates a specific immune response. PresenceInnate Immunity: Innate immunity is always present in the body. Adaptive Immunity:Adaptive immunity only occurs in response to exposure to an external factor. ResponseInnate Immunity:Since innate immunity provides the first line defense against the pathogens, it generates a rapid response. Adaptive Immunity: Adaptive immunity is delayed 5-6 days. ComponentsInnate Immunity:Plasma proteins, phagocytes, physical and chemical barriers are the components of the innate immunity. Adaptive Immunity: Humoral and cell-mediated immunity are the components of the adaptive immunity. Physical and Chemical BarriersInnate Immunity:Temperature, pH, skin, and mucous membranes are the barriers of the innate immunity. Adaptive Immunity: Lymph nodes, spleen, and lymphoid tissues are the barriers of the adaptive immunity. Memory CellsInnate Immunity:Innate immunity does not develop memory cells. Adaptive Immunity:Adaptive immunity develops memory cells. DiversityInnate Immunity:Innate immunity possesses a less diversity. Adaptive Immunity: Adaptive immunity possesses a higher diversity. PotencyInnate Immunity: Innate immunity is less potent. Adaptive Immunity:Adaptive immunity exhibits a higher potency. Allergic ReactionsInnate Immunity: Innate immunity does not produce allergic reactions. Adaptive Immunity:Adaptive immunity develops allergic reactions; immediate and delayed hypersensitivity. Activation of the Complement SystemInnate Immunity:Innate immunity activates the complement system through the alternative and lectin pathway. Adaptive Immunity:Adaptive immunity activates the complement system through the classical pathway. Time SpanInnate Immunity: Once developed for a particular pathogen, the innate immunity remains throughout the lifetime. Adaptive Immunity:Adaptive immunity can last for the lifetime or for a short period of time. InheritanceInnate Immunity: Innate immunity is inheritable. Adaptive Immunity:Adaptive immunity is not inheritable. ExamplesInnate Immunity: The redness and swelling caused by white blood cells around a wound is an example of an innate immune response. Adaptive Immunity:Vaccination against a virus is an example of adaptive immunity. ConclusionInnate and adaptive immunity are the two types of mechanisms of the immune system of animals. They protect the body against pathogens. Innate immunity generates first line and second line immune responses. Adaptive immunity generates third line immune responses. The immune response is non-specific in innate immunity, and it is specific in adaptive immunity. The main difference between innate and adaptive immunity is the type of mechanisms and the specificity of the immune responses generated by them. Image Courtesy:1. “Innate Immune cells” By Template drawing and caption text from “The Immune System” (pdf) (Public Domain) via
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