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22: Adaptive Immunity I

Last updated

Jan 22, 2025
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- 21.E: Innate Immune Defenses II (Exercises)
- 22.1: Adaptive Immune Defenses - Overview

Ying Liu
City College of San Francisco

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People living in developed nations and born in the 1960s or later may have difficulty understanding the once heavy burden of devastating infectious diseases. For example, , a deadly viral disease, once destroyed entire civilizations but has since been eradicated. Thanks to the vaccination efforts by multiple groups, including the World Health Organization, Rotary International, and the United Nations Children’s Fund (UNICEF), smallpox has not been diagnosed in a patient since 1977. is another excellent example. This crippling viral disease paralyzed patients, who were often kept alive in “iron lung wards” as recently as the 1950s (Figure $\PageIndex{1}$ ). Today, vaccination against polio has nearly eradicated the disease. Vaccines have also reduced the prevalence of once-common infectious diseases such as chickenpox, German measles, measles, mumps, and whooping cough. The success of these and other vaccines is due to the very specific and adaptive host defenses that are the focus of this chapter.

Innate Nonspecific Host Defenses described innate immunity against microbial pathogens. Higher animals, such as humans, also possess an adaptive immune defense, which is highly specific for individual microbial pathogens. This specific adaptive immunity is acquired through active infection or vaccination and serves as an important defense against pathogens that evade the defenses of innate immunity.

Photo of a room full of patients in large chambers that cover their entire bodies. — Figure $\PageIndex{1}$ : Polio was once a common disease with potentially serious consequences, including paralysis. Vaccination has all but eliminated the disease from most countries around the world. An iron-lung ward, such as the one shown in this 1953 photograph, housed patients paralyzed from polio and unable to breathe for themselves.

22.1: Adaptive Immune Defenses - Overview
Adaptive immunity is defined by two important characteristics: specificity and memory. Specificity refers to the adaptive immune system’s ability to target specific pathogens, and memory refers to its ability to quickly respond to pathogens to which it has previously been exposed. For example, when an individual recovers from chickenpox, the body develops a memory of the infection that will specifically protect it from the causative agent if it is exposed to the virus again later.
22.2: Antigens
Adaptive immunity is defined by two important characteristics: specificity and memory. Specificity refers to the adaptive immune system’s ability to target specific pathogens, and memory refers to its ability to quickly respond to pathogens to which it has previously been exposed. For example, when an individual recovers from chickenpox, the body develops a memory of the infection that will specifically protect it from the causative agent if it is exposed to the virus again later.
22.3: Antibodies
Adaptive immunity is defined by two important characteristics: specificity and memory. Specificity refers to the adaptive immune system’s ability to target specific pathogens, and memory refers to its ability to quickly respond to pathogens to which it has previously been exposed. For example, when an individual recovers from chickenpox, the body develops a memory of the infection that will specifically protect it from the causative agent if it is exposed to the virus again later.
22.4: Antigen-Antibody Interactions
Adaptive immunity is defined by two important characteristics: specificity and memory. Specificity refers to the adaptive immune system’s ability to target specific pathogens, and memory refers to its ability to quickly respond to pathogens to which it has previously been exposed. For example, when an individual recovers from chickenpox, the body develops a memory of the infection that will specifically protect it from the causative agent if it is exposed to the virus again later.
22.5: Major Histocompatibility Complexes (MHC)
Major histocompatibility complex (MHC) molecules are expressed on the surface of healthy cells, identifying them as normal and “self” to natural killer (NK) cells. MHC molecules also play an important role in the presentation of foreign antigens, which is a critical step in the activation of T cells and thus an important mechanism of the adaptive immune system.
22.6: Antigen Presenting Cells (APC)
Major histocompatibility complex (MHC) molecules are expressed on the surface of healthy cells, identifying them as normal and “self” to natural killer (NK) cells. MHC molecules also play an important role in the presentation of foreign antigens, which is a critical step in the activation of T cells and thus an important mechanism of the adaptive immune system.
22.E: Adaptive Immunity I (Exercises)

Thumbnail: From left to right: erythrocyte, platelet and lymphocyte. (Public Domain; The National Cancer Institute at Frederick).

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