12: Introduction to Adaptive Immunity — Read

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12.1: An Overview of Innate and Adaptive Immunity
Innate immunity is an antigen-nonspecific defense mechanisms that a host uses immediately or within several hours after exposure to almost any microbe. This is the immunity one is born with and is the initial response by the body to eliminate microbes and prevent infection. Innate immunity can be divided into immediate innate immunity and early induced innate immunity.
12.2: Antigens and Epitopes
An antigen is defined as a substance that reacts with antibody molecules and antigen receptors on lymphocytes. An immunogen is an antigen that is recognized by the body as non-self and stimulates an adaptive immune response. Chemically, antigens are large molecular weight proteins and polysaccharides. The actual portions or fragments of an antigen that react with receptors on B-lymphocytes and T-lymphocytes, as well as with free antibody molecules, are called epitopes.
12.3: Major Cells and Key Cell Surface Molecules Involved in Adaptive Immune Responses
We will now take a look at major cells and key cell-surface molecules involved in adaptive immune responses.
12.4: The Lymphoid System
The body uses the lymphoid system to enable lymphocytes to encounter antigens and it is here that adaptive immune responses are initiated. The lymphoid system consists of primary lymphoid organs, secondary lymphoid organs, and lymphatic vessels. The bone marrow and the thymus constitute the primary lymphoid organs. While both B-lymphocytes and T-lymphocytes are produced from stem cells in the bone marrow, B-lymphocytes mature in the bone marrow and T-lymphocytes migrate to the thymus to mature.
12.5: An Overview of the Steps Involved in Adaptive Immune Responses
The immune responses are carefully regulated by a variety of mechanisms. They are turned on only in response to an antigen and are turned off once the antigen has been removed. The immune responses are also able to discriminate between self and non-self in order to prevent autoimmune tissue damage. During the random gene-splicing reactions mentioned earlier, some lymphocytes are bound to produce receptors that fit the body's own proteins and polysaccharides.
12.E: Introduction to Adaptive Immunity (Exercises)
These are homework exercises to accompany Kaiser's "Microbiology" TextMap. Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell (unicellular), cell clusters or no cell at all (acellular). This includes eukaryotes, such as fungi and protists, and prokaryotes. Viruses and prions, though not strictly classed as living organisms, are also studied.

Thumbnail: Anterior view of chest showing location and size of adult thymus. (CC-BY 3.0; LearnAnatomy)

This page titled 12: Introduction to Adaptive Immunity was last modified on Fri, 10 Oct 2025 22:57:17 GMT and is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Gary Kaiser via source content that was edited to the style and standards of the LibreTexts platform.

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