Defending Your Body

To defend against invaders—bacteria, viruses, and other pathogens—our bodies have two levels of defense.

  1. Nonspecific defense mechanisms
  2. Specific defense mechanisms (a.k.a. the immune system)

Specific Defense Mechanisms: The Immune Response

Discovery of Vaccination

Shows a human knee infected with smallpox. Depicts a human hand infected with cowpox.

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Jenner's Dream Accomplished: the Eradication of Smallpox

Major Players in the Specific Defense Mechanism: Lymphocytes

Shows how lymphocytes are derived from bone marrow.

Part of figure 18.2, Purves's Life: The Science of Biology, 7th Edition

Origin of Lymphocytes

Shows how B and T cells are derived from bone marrow, focusing on the location of development.

Figure 43.8, page 846, Campbell's Biology, 5th Edition

The Human Lymphatic System

Shows lymph capilaries in the context of the circulatory and lymphatic systems.

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The Main Players

Highlights the different parts of the human lymphatic system.

Figure 18.1, Purves's Life: The Science of Biology, 7th Edition

Antibodies (Immunoglobulins)

Shows the basic structure of an antibody.

Figure 43.15(a), page 852, Campbell's Biology, 5th Edition

How an Antibody Works

Shows the structure of antibodies and how they bind to antigens.

Figure 18.10, Purves's Life: The Science of Biology, 7th Edition

Five Classes of Antibodies

Class General Structure Location Function
IgG Monomer The structure of a monomer antibody. Free in plasma; about 80 % of circulating antibodies Most abundant antibody in primary and secondary responses; crosses placenta and provides passive immunization to fetus
IgM Pentamer The structure of a pentamer antibody. Surface of B cell; free in plasma Antigen receptor on B cell membrane; first class of antibodies released by B cells during primary response
IgD Monomer The structure of a monomer antibody. Surface of B cell Cell surface receptor of mature B cell; important in B cell activation
IgA Dimer The structure of a dimer antibody. Monomer found in plasma; polymers in saliva, tears, milk, and other body secretions Protects mucosal surfaces; prevents attachment of pathogens to epithelial cells
IgE Monomer The structure of a monomer antibody. Secreted by plama cells in skin and tissues lining gastrointestinal and respiratory tracts Found on mast cells and basophils; when bound to antigens, triggers release of histamine from mast cell or basophil that contributes to inflammation and some allergic responses

Antibodies as Receptors

Shows a receptor antibody interacting with a B cell and an antigen.

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Antibodies as Effectors

Shows an effector antibody helping in the destruction of an antigen-bearing microbe.

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