Chapter 021

The Human Body in Health and Illness, 4th edition

Barbara Herlihy

Chapter 21:Immune System

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Lesson 21-1 Objectives

• Differentiate between specific and nonspecific immunity.

• Describe the process of phagocytosis.• Explain the causes of the signs of

inflammation.• Explain the role of fever in fighting infection.• Explain the role of T cells in cell-mediated

immunity.Copyright © 2011, 2007 by Saunders,

an imprint of Elsevier Inc. All rights reserved.

2

Lesson 21-1 Objectives (cont’d.)

• Explain the role of B cells in antibody-mediated immunity.

• Differentiate between genetic immunity and acquired immunity.

• Describe naturally and artificially acquired active and passive immunity.

• Identify the steps in the development of anaphylaxis.

Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights

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Immune System: Classification

• Specific immunity protects against one substance.

• Nonspecific immunity protects against many substances.


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Immunity: Lines of Defense

• Nonspecific immunity– First line: Mechanical or chemical barriers, reflexes– Second line: Phagocytosis, inflammation, fever,

protective proteins, natural killer cells

• Specific immunity– Third line: B and T lymphocytes or B and T cells


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Nonspecific Immunity: Lines of Defense


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Second Line of Defense: Phagocytosis

• Leukocytes go to site of infection.– Diapedesis– Chemotaxis

• Leukocytes “eat”– Pathogens – Cellular debris


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Second Line of Defense: Inflammation

• Classic signs– Redness– Heat – Swelling– Pain


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Second Line of Defense: Fever (Pyrexia)

• Phagocytosis releases pyrogens.

• Pyrogens reset body thermostat upward.

• Body temperature rises.

• Antipyretics can lower temperature.


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Second Line of Defense: Protective Proteins

• Interferons are secreted by cells infected by a virus.

• Interferons protect other cells from viral replication.

• Complement proteins assist WBCs.


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Second Line of Defense: NK Cells

• A lymphocyte that acts nonspecifically

• Effective against many microbes and certain cancer cells


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Specific Immunity: 3rd Line of Defense

• T cells– Cell-mediated

immunity

• B cells– Antibody-mediated

immunity

• Macrophages– Help activate T and B

cellsCopyright © 2011, 2007 by Saunders,

an imprint of Elsevier Inc. All rights reserved.

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T-Cell Activation• Macrophage

ingests antigen• Antigen

presentation• Clone produced

– Killer T cells– Helper T cells– Suppressor T cells– Memory T cells


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B-Cell Activation• Macrophage

ingests antigen• Antigen

presentation• B cells and helper T

cells activated• Clone formed

– Plasma cells– Memory B cells


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Antigen, Antibody, Immunoglobulin• Antigen: Stimulates formation of antibodies • Antibody: Secreted by B cells, also called

immunoglobulins• Antigen-antibody interaction agglutination• Important immunoglobulins

– Immunoglobulin G (IgG)– Immunoglobulin A (IgA)– Immunoglobulin M (IgM)– Immunoglobulin E (IgE)


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Why is Secondary Response Stronger than Primary Response?


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Types of Immunity

• Genetic: Inborn and species-specific

• Acquired: How do you get it?– Naturally– Artificially


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Naturally Acquired Immunity • Active: You are

exposed to the antigen and you produce antibodies.– Exposure to a virus

• Passive: Someone else makes antibodies.– From mother


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Artificially Acquired Immunity

• Active– Vaccines– Toxoids

• Passive– Immune globulin

(antibodies made by others)

– Antitoxins, antivenoms


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Allergic Reaction: Delayed

• Occurs in about 48 hours• Usual cause is repeated exposure of skin to

irritants (household detergents, poison ivy)• Activates T cells, causing skin eruptions and

inflammation (contact dermatitis)


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Immediate Hypersensitivity Reaction: Anaphylaxis

• Bee venom IgE • IgE binds to mast cells.• Second sting: Venom

binds to IgE on mast cell.

• Mast cells release histamine.

• Histamine drops BP and impairs breathing.


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Other Immunological Responses

• Autoimmune diseases: Develop in response to self-attack, or autoimmunity

• Organ rejection: Recipient’s immune system recognizes donated organ as foreign, mounts immune attack against it


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Technology

Chapter 021