12.9.3 Antibody Mechanisms Flashcards Preview

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Flashcards in 12.9.3 Antibody Mechanisms Deck (12)
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1
Q

Antibody Mechanisms

A
  • Antibodies make up a group of proteins called immunoglobulins. A typical antibody is made up of four polypeptides (two identical heavy chains and two identical light chains) held together by disulfide bonds.
  • Plasma cells secrete antibodies as a part of the humoral immune response. Antibodies function by attaching to antigens and signaling the body’s defenses.
  • There are five major classes of antibodies based on the five types of heavy-chain constant regions and their different functions. These classes are IgM, IgG, IgA, IgD, and IgE.
  • Major mechanisms of antibody action include neutralization, opsonization, agglutination, precipitation, and complement activation.
2
Q

antibodies

A
- Antibodies are a group of proteins secreted by plasma cells as a part of the humoral response. A general antibody consists of four polypeptide chains that are held together forming a Y-shaped molecule. The two upper ends of the antibody in the diagram to the left are the antigen-binding sites. Notice that both of these regions are made up of the variable regions of all four polypeptide chains. The lower end of the antibody, made up of heavy-chain constant regions, does not bind to antigens, but determines the class of the
antibody.
3
Q

neutralization

A
  • One method of antibody action is neutralization.
    Neutralization occurs when the antibody binds to the antigen and blocks its activity. When the antigen is covered and neutralized by antibodies, it can then easily undergo phagocytosis by a macrophage. Antibodies enhance macrophage ingestion of antigens in a process called opsonization.
4
Q

agglutination and percipitation

A
  • Antibodies also mediate agglutination. Agglutination is the clumping of antigen-bearing particles such as viruses and bacteria. Because antibodies have at least two antigen binding regions, they can bind to more than one antigen-bearing particle, causing clumping. When a clump has been formed, it is easily removed by phagocytosis.
  • Similarly, antibodies can also cause the precipitation of
    soluble antigens. Antibodies bind to and cross-link antigens dissolved in body fluids, forming a precipitate that is easily removed by macrophages.
5
Q

complement system

A
  • Antibodies can also activate the complement system. The complement system consists of at least 20 different proteins in an inactive form. When the first proteins of the complement system are activated, a cascade of activation takes place, ending with the lysis of infected or pathogenic cells.
  • Antibodies already bound to the antigen activate the
    complement system. A complement protein activates as it binds to two antibodies, as shown in the diagram. Once activated, the bound protein activates other complement proteins. Eventually, activated complement proteins assemble to form a membrane attack complex (MAC). The MAC disrupts and forms pores in the plasma membrane of the cell, eventually causing lysis of the cell
6
Q

The reaction that is used to type blood is

A
  • agglutination
7
Q

In the presence of a large cell such as a protozoan, antigens would activate ____________________, which penetrates the cell membrane of the pathogen and cause it to burst.

A
  • the complement system
8
Q

Which of the following classes of antibodies exists as a pentamer?

A
  • IgM
9
Q

When antibodies bind to an antigen and block its activity, this is known as

A
  • neutralization
10
Q

Which of the following mechanisms are not used by antibodies to destroy cells?

A
  • Lysis
11
Q

Complement proteins are able to do all but which of the following?

A
  • Stimulate antibody production
12
Q

True or false?

Antibodies typically work by destroying the microbe/antigen.

A
  • false

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