and acquired immunity. AN INTRODUCTION - Bethel … © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin

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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

PowerPoint® Lecture Slide Presentation prepared by Christine L. Case

MicrobiologyB.E Pruitt & Jane J. Stein

AN INTRODUCTIONEIGHTH EDITION

TORTORA • FUNKE • CASE

Chapter 17Specific Defenses of the Host:

The Immune Response


Differentiate between innate and acquired immunity.


Specific Defenses of the Host:The Immune Response

• Innate (nonspecific) Defenses against any pathogen, genetically predetermined resistance (gender, age, nutrition)

• Immunity Specific antibody and lymphocyte response to an antigen (counteract infection)

• Antigen (Ag) A substances that causes the body to produce specific antibodies or sensitized T cells

• Antibody (Ab) Proteins made in response to an antigen

Differentiate between immunity and nonspecific resistance.


Terminology

• Acquired immunity Resistance to infection during life of host

• Naturally acquired Resulting from infection, may beactive immunity long-lasting

• Serology Study of reactions between antibodies and antigens

• Antiserum Generic term for serum because it contains Ab

• Globulins Serum proteins• Gamma (γ) globulin Serum fraction containing Ab


Serum Proteins – separation by gel electrophoresis

Figure 17.2

• Immune serum globulinor gamma globulin Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

The Immune Response

• Acquired immunity Developed during an (vaccination) individual's lifetime

• Humoral immunity Involves Ab (antibodies) (in body fluids) produced by B cells

• Defend against bacteria, viruses, toxins in blood plasma and lymph

• Cell-mediated immunity Involves T cells (certain lymphocytes)

• Response to intracellular bacteria, viruses, parasites, transplanted tissue, cancer cells

Differentiate between humoral (antibody-mediated) and cell-mediated immunity.

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Acquired Immunity

• Naturally acquired active immunity• Resulting from infection

• Naturally acquired passive immunity• Transplacental or via colostrum

• Artificially acquired active immunity• Injection of Ag (antigen - vaccination)

• Artificially acquired passive immunity• Injection of Ab (antibody) or antiserum

Contrast the four types of acquired immunity.


Antigenic Determinants (epitopes)• Antibodies recognize and react with antigenic determinants or

epitopes (specific regions on surface of antigen).• Antigens cause body to produce specific antibodies. Are

components of invading microbes generally.

Figure 17.3

Define antigen and hapten.


Haptens

Figure 17.4

• Hapten is a molecule too small to stimulate antibody formation by itself, until combined with larger carrier molecule like a serum protein, becoming an antigen.


Antibody Structure (Immunoglobulin) – protein produced by B cells in response to antigen

Figure 17.5a-c

Explain the function of antibodies and describe their structural and chemical characteristics.


• Monomer (single bivalent antibody unit)

• 80% of serum antibodies• Fix complement• In blood, lymph, intestine• Cross placenta• Enhance phagocytosis;

neutralize toxins & viruses; protects fetus & newborn

• Half-life = 23 days

IgG antibodies

Name one function for each of the five classes of antibodies.


• Pentamer (5 monomers)• 5-10% of serum

antibodies• Fix complement• In blood, lymph, on B

cells• Agglutinates microbes;

first Ab produced in response to infection

• Half-life = 5 days

IgM antibodies

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• Dimer• 10-15% of serum

antibodies• In secretions• Mucosal protection• Half-life = 6 days

IgA antibodies


• Monomer• 0.2% of serum antibodies• In blood, lymph, on B cells• On B cells, initiate immune

response• Half-life = 3 days

IgD antibodies


• Monomer• 0.002% of serum

antibodies• On mast cells and

basophils, in blood• Allergic reactions; lysis of

parasitic worms• Half-life = 2 days• Involved in allergic

reactions

IgE antibodies



• Humoral (fluid) immunity involves antibodies produced by B cells

• Bone marrow gives rise to B cells.• Mature B cells migrate to lymphoid organs.• A mature B cells recognizes epitopes (antigen

receptor).

Clonal Selection

Name the function of B cells.


• Differentiation of T cells and B cells, both from stem cells in adult red bone marrow or fetal liver

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•Apoptosis –normal B cell below, B cell above undergoing apoptosis (bubble-like blebs)

•Programmed cell death to prevent overpopulation of B cells

Define apoptosis, and give a potential medical application.


Clonal Selection & Differentiation of B cells

Figure 17.8

•Each particular B cell recognizes only one type of antigen, activating the B cell•Produces clone of plasma cells (antibodies) and memory cellsDescribe the clonal selection theory.


Self-tolerance

• Antigen-antibody complex can result in agglutination, inflammation, lysis

• Body doesn't make Ab against self• Clonal deletion

• The process of destroying B and T cells that react to self antigens

• Amount of antibody in serum called antibody titer

Explain how an antibody reacts with an antigen; identify the consequences of the reaction.


Protective Mechanism of Ag-Ab Binding

Figure 17.9

•Result of antigen-antibody binding

•Tags foreign cells and molecules for destruction by phagocytes and complement (serum proteins for phagocytosis and lysis of cells)


Primary and secondary immune response to antigen

• IgM appears first (primary response)

• IgG follows and provides longer-term immunity (high antibody titer)

Figure 17.10

Distinguish a primary from a secondary immune response.


Monoclonal Antibodies

• Hybridomas are produced by fusing a cancer cell with an Ab-secreting plasma cells

• The hybridoma cell culture is immortal and produces monoclonal Abs (Mabs) – serologic identification tests, prevent tissue rejections

• Immunotoxins: Mabs conjugated with a toxin to target cancer cells

• Chimeric Mabs: Genetically modified mice that produce Ab with a human constant region

• Humanized Mabs: Mabs that are mostly human, except for mouse antigen-binding

Define monoclonal antibodies and identify their advantage over conventional antibody production.

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Monoclonal Antibodies


• Interleukin-1 Stimulates TH cells• Interleukin-2 Activates TH, B, TC, and NK cells• Interleukin-12 Differentiation of CD4 cells• γ-Interferon Increase activity of macrophages• Chemokines Cause leukocytes to move to an

infection

Immune system cells communicate via cytokines

Identify at least one function of each of the following in cell-mediated immunity: cytokines, interleukins, interferons.


Chemical messengers: Cytokines

• Cells of immune system communicate via cytokines• Interleukins (IL) are cytokines between leukocytes• Interferons protect cells against viruses• Chemokines cause leukocytes to move to infection site


• Specialized lymphocytes, mostly T cells, respond to intracellular Ags

• After differentiating in the thymus, T cells migrate to lymphoid tissue

• T cells differentiate into effector T cells when stimulated by an Ag

• Some effector T cells become memory cells

Cell-Mediated Immunity


• M (microfold) cells in• Peyer's patches which contains• Dendritic cells which are antigen-presenting cells

and• T cells

Pathogens entering the gastrointestinal or respiratory tracts pass through:


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Dendritic cells present antigens

Figure 17.12 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

• Helper T Cells (CD4, TH)• TH1 Activate cells related to cell-mediated

immunity• TH2 Activate B cells to produce eosinophils, IgM,

and IgE• Cytotoxic T Cells (CD8, TC)

• Destroy target cells with perforin

T CellsDescribe at least one function for each of the following: TH1 cell, TH2 cell, TCcell, TD cell, TS cell, APC, MHC,activated macrophage, NK cell.


• Delayed Hypersensitivity T Cells (TD)• Associated with allergic reaction, transplant

rejection, and tuberculin skin test• Suppressor T cells (TS)

• Turn off immune response when Ag no longer present

T Cells


Helper T Cells

Figure 17.13


Cell-mediated Cytotoxicity

Figure 17.14 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Nonspecific Cells – Activated Macrophages

• Activated macrophages: Macrophages stimulated by ingesting Ag or by cytokines

• Natural killer cells: Lymphocytes that destroy virus-infected cells, tumor

Figure 17.15

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T-independent Antigens

B cell

•T-indep. antigen has repeating units that cross-link several antigen receptors on same B cell

Compare and contrast T-dependent antigens and T-independent antigens.Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Describe the role of antibodies and NK cells in antibody-dependent cell-mediated cytotoxicity.


T-independent Antigens

Figure 17.16

•How helper T cells may activate B cells to make antibodies against T-dependent antigens


Antibody-Dependent Cell-Mediated Cytotoxicity

Figure 17.18

•Eosinophils adhering to larval stage of parasitic fluke

Compare and contrast cell-mediated and humoral immunity.


Duality of immune system

Documents

and acquired immunity. AN INTRODUCTION - Bethel … © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2004 Pearson Education, Inc., publishing as Benjamin