Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Chapter 67 Review of the Immune System

2Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Review of the Immune System  Two types of immune responses  Natural immunity (innate)  Specific acquired immunity Cell-mediated Cell-mediated Antibody-mediated: humoral Antibody-mediated: humoral

3Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Immune System: Cells  B lymphocytes (B cells)  Make antibodies  Cytolytic T lymphocytes  Cytolytic T cells, CD8 cells  Do not produce antibodies  Attack and kill target cells directly  Helper T lymphocytes  Helper T cells, CD4 cells Antibody production by B cells Antibody production by B cells Promote delayed-type hypersensitivity (DTH) Promote delayed-type hypersensitivity (DTH) Activation of cytolytic T cells Activation of cytolytic T cells

4Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Immune System: Cells  Helper T lymphocytes  Helper T cells, CD4 cells Required for an effective immune response Required for an effective immune response Antibody production by B cells Antibody production by B cells Promote DTH Promote DTH Activation of cytolytic T cells Activation of cytolytic T cells

5Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Immune System: Cells  Macrophages  Begin in bone marrow, enter blood as monocytes, and infiltrate tissues, where they evolve into macrophages  Principal scavengers of the body  Specific acquired immunity Activation of T cells Activation of T cells Final mediators of DTH Final mediators of DTH Phagocytize cells tagged with antibodies Phagocytize cells tagged with antibodies  Also play key roles in natural immunity and inflammation

6Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Fig. 67–1. Maturation of blood cells.

7Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Immune System: Cells  Dendritic cells  Mast cells and basophils  Mediate immediate hypersensitivity reactions  Neutrophils (polymorphonuclear leukocytes)  Phagocytize bacteria and other foreign particles  Eosinophils  Attack and destroy foreign particles that have been coated with antibodies of the immunoglobulin (Ig)E class

8Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Antibodies  Alternative names  Immunoglobulins  Gamma globulins  Family of structurally related glycoproteins  Mediate humoral immunity  Recognize and bind with specific antigens  Produced by B lymphocytes  Five classes of antibodies  IgA, IgD, IgE, IgG, and IgM

9Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Fig. 67–2. Antibody structure.

10Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Antigens  Molecules that induce specific immune responses  May trigger production of antibodies or cytotoxic T cells, or both  Antibodies recognize and bind selected small portions of the antigen  More than one antibody can bind to the antigen

11Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Fig. 67–3. Memory and time limitation of immune responses.

12Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Characteristic Features of the Immune Response  Specificity  Immune responses are triggered by specific antigens  Diversity  Millions of different antigenic determinants  Memory  Exposure to an antigen affects the immune system such that re-exposure produces a faster, larger, and more prolonged response  Time limitation  Selectivity for antigens of nonself origin  Targets only foreign antigens (normal conditions)

13Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Phases of the Immune Response  Recognition phase  Antigen recognition by B cells and T cells  Activation phase  Proliferation  Differentiation of activated lymphocytes  Effector phase  Elimination of antigen

14Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Antibody-Mediated (Humoral) Immunity  Production of antibodies  Interaction of three types of cells B cells B cells  Make antibodies Helper T cells (CD4 cells) Helper T cells (CD4 cells)  Stimulate B cells Antigen-presenting cells (macrophage or dendritic) Antigen-presenting cells (macrophage or dendritic)  Activate CD4 cells

15Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Antibody-Mediated (Humoral) Immunity  Antibody effector mechanisms  Opsonization of bacteria  Activation of the complement system  Neutralization of viruses and bacterial toxins

16Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Fig. 67–4. Major events in antibody-mediated (humoral) immunity.

17Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Cell-Mediated Immunity  Two branches  Delayed-type hypersensitivity (DTH) Activation of helper T cells Activation of helper T cells Activation of macrophages Activation of macrophages  Cytolytic T lymphocytes (CTLs, CD8 cells) Activation of cytolytic T cells Activation of cytolytic T cells Recognition of virally infected target cells Recognition of virally infected target cells Mechanism of cell kill Mechanism of cell kill  Binding of a CTL to its target cell  Release of mediators that kill the target Cause target cell lysis Cause target cell lysis

18Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Fig. 67–5. Cell-mediated immunity: delayed-type hypersensitivity.

19Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Fig. 67–6. Cell-mediated immunity: cytolytic T cells.