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The Immune System

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39.1 The Evolution of Immunity

1. All animals have immunity, which is based on the ability to distinguish self from nonself antigens.Art Quiz
Immune System Evolution
2. All animals have innate immunity, but vertebrates alone have adaptive immunity. 
3. Phagocytes and antimicrobial peptides provide invertebrates' innate immunity. 

39.2 Innate Defenses Are Nonspecific and Act Early

4. Skin, mucous membranes, tears, earwax, and cilia block pathogens. 
5. Phagocytes and antimicrobial substances take part in inflammation, which is an immediate reaction to injury. These protections recognize patterns of molecules that are unique to pathogens. 
6. Complement proteins interact in a cascade that bursts bacterial cells.Animation
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Nonspecific Defense Mechanisms

39.3 Adaptive Defenses Are Specific and Act Later

7. Macrophages are antigen-presenting cells, engulfing, processing, and displaying foreign antigens held in place by major histocompatibility complex molecules.Animation
8. A helper T cell binding to the antigen-presenting cell triggers the adaptive immune response. 
9. B cells, when activated by helper T cells, proliferate and differentiate into plasma cells, which secrete antibodies, and memory B cells.Art Quiz
Monoclonal Antibody Production
10. An antibody is a Y-shaped protein composed of two heavy chains and two light chains. Each chain has a constant amino acid sequence and a variable sequence. The tips form an antigen binding site. Antibodies bind antigens and form complexes that attract other immune system components. Antibody molecules are incredibly diverse because DNA segments shuffle during early B cell development. This is the humoral immune response.Animation
B Cells
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Humoral Immunity
11. T cells carry out the cellular immune response. They are educated in the thymus gland to recognize self. Helper T cells activate other T cells and B cells. Cytotoxic T cells release biochemicals that bore into bacteria, kill them, and also destroy cells infected with viruses. T cells secrete cytokines, which control communication within the immune system.Essential Study Partner
Immune Cells
T Cells
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Cell-Mediated Immunity
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T Cells vs. B Cells
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Activation of T Cells

39.4 The Human Immune System Throughout Life

12. In the fetus, T cells become able to distinguish self from non-self in the thymus. 
13. A pregnant woman's immune system dampens, but fetal cells in her bloodstream can cause problems. 
14. A baby gets antibodies from the mother, which is passive immunity, then begins to make its own. Immune function begins to wane in early adulthood.Essential Study Partner
Active vs. Passive Immunity

39.5 The Unhealthy Immune System

15. HIV enters helper T cells and uses them to reproduce, killing them directly. The virus activates apoptosis in cytotoxic T cells.Essential Study Partner
Immune Abnormalities
16. Immune deficiency can be inherited, and some types are treatable with gene therapy. 
17. Autoimmunity results when the immune system produces autoantibodies, which attack the body's tissues. 
18. An allergy is an immune reaction to a harmless substance. An allergen activates IgE antibodies, which cause mast cells to release allergy mediators.Art Quiz
Allergic Reaction

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