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Chapter 15
Host Defenses II: Specific Immunity and Immunization
Chapter Outline
15.1. Specific Immunity: The Third and Final Line of Defense
A. Acquired specific immunity consists of a dual system of the T and B lymphocytes
1. Immunocompetence
2. Two features of the third line of defense are:
a. Specificity
b. Memory
B. Stages of immunologic development and interaction
1. Lymphocyte development and differentiation
2. The presentation of antigens
3. The challenge of B and T lymphocytes by antigens
4. B lymphocytes and the production and activities of antibodies
5. T lymphocyte responses
15.2. An Overview of Specific Immune responses
A. Development of the dual lymphocyte system
1. T-cells mature in the thymus
2. B-cells mature in the bone marrow
B. Entrance and presentation of antigens and clonal selection
C. Activation of lymphocytes and clonal expansion
D. Products of B lymphocytes: Antibody structure and functions
E. How T cells respond to antigen: Cell-mediated immunity (CMI)
F. Essential preliminary concepts for understanding immune reactions
G. Receptors on cell surfaces involved in recognition of self and non-self
1. Major functions of receptors:
a. Attach to nonself molecules
b. Binding to cell surface receptors that indicate self, such as MHC
molecules
c. Receiving and transmitting chemical messages to coordinate the
response
d. Aiding in cellular development
2. Major histocompatibility complex (MHC)
a. White blood cell markers called the human leukocyte antigen (HLA)
system
b. MHC profiles of individuals
c. Three MHC classes, I, II, and III
3. Lymphocyte receptors and specificity to antigen
H. The origin of diversity and specificity in the immune response
1. The clonal selection theory and lymphocyte development
a. Lymphocyte specificity is pre-programmed
b. Each type of lymphocyte has a single specificity
i. When these cells give rise to a line of specific lymphocytes
with the same specificity
ii. These are known as clones
d. Tolerance to self principle
i. Clones that react to self are destroyed
ii. This is known as clonal deletion
1-1
2. The specific B-cell receptor: An immunoglobulin molecule
a. Immunoglobulins are glycoproteins
b. Antigen binding site
c. Variable region
d. Constant region
3. T-cell receptors
15.3. The Lymphocyte Response System in Depth
A. Specific events in B-cell maturation
1. Bone marrow stromal cells
a. Dissemination to spleen, lymph nodes, and GALT
2. Specific events in T-cell maturation
a. Directed by thymus
b. Mature T cells express CD4 or CD8 coreceptors
B. Entrance and processing of antigens and clonal selection
1. Antigenicity
2. Antigens or immunogens
3. Characteristics of antigens
a. Materials that serve as antigens:
i. Proteins and polypeptides
ii. Lipoproteins
iii. Glycoproteins
iv. Nucleoproteins
v. Polysaccharides
b. Effects of molecular shape and size
i. Portion of antigen molecule that is recognized by lymphocytes
is known as the epitope
ii. Haptens or partial antigens
iii. Special types of antigens
1. Alloantigens
2. Superantigen bacterial toxins
3. Allergens
15.4. Cooperation in Immune Reactions to Antigens
A. The role of antigen processing and presentation
1. Antigen-processing cells
2. Dendritic cells
B. Presentation of antigen to the lymphocyte and its early consequences
1. T-cell-dependent antigens
2. T helper cells
3. Roles of interleukin-1 and interleukin-2
4. T-cell-independent antigens
15.5. B-Cell Response
A. Activation of B lymphocytes: Clonal expansion and antibody production
1. Clonal selection and binding of antigen
2. Antigen processing and presentation
3. B-cell/T-cell recognition and cooperation
4. B-cell activation
5. Clonal expansion
6. Antibody production and secretion
B. Products of B-lymphocytes: Antibody structure and functions
1. The structure of immunoglobulins
a. Most common class is IgG
1-2
b. Antigen-binding fragment
c. Crystallizable fragment
2. Antibody-antigen interactions and the function of the Fab
a. Opsonization by opsonin
b. Agglutination by antibodies
c. Neutralizing antibodies
d. Antitoxins
3. Functions of the Fc fragment
4. Accessory molecules on immunoglobulins
a. J chain joining IgA and IgM
b. Secretory component moves IgA across mucous membranes
5. The classes of immunoglobulins: Isotypes
a. IgG: most prevalent class
b. IgA: found in blood, serum and mucous secretions including saliva,
tears, etc.
c. IgM: a pentamer molecule; 10 binding sites gives it a tremendous
capacity for binding antigen
d. IgD: B-cell receptor for antigen on cell surfaces
e. IgE: involved in allergic reactions; basophils and mast cell activation;
causes anaphylaxis, asthma reactions
6. Evidence of antibodies in serum
a. Antiserum
b. Immunoglobins
c. Alpha, beta, and gamma globulins
7. Monitoring antibody production over time: Primary and secondary
responses to antigens
a. Titer (antibody levels)
b. Primary response and latent period
c. Secondary and anamnestic responses (basis of vaccination)
15.6. T-Cell Response
A. Cell-mediated immunity (CMI)
1. The activation of T cells and their differentiation into subsets
a. T-Helper (TH) cells
b. Cytotoxic T (TC) cells: Cells that kill other cells
i. Killer T cells
ii. Perforin used to attack target cells
iii. Causes cell death or apoptosis
iv.Target virally infected cells, cancer cells
v. Responsible for graft rejections
2. Other types of killer cells
a. Natural killer (NK) cells
15.7. A Practical Scheme for Classifying Specific Immunities
A. Active, passive, natural, or artificial
B. Natural active immunity: Getting the infection
C. Natural passive immunity: Mother to child
D. Artificial immunity: Immunization
E. Vaccination: Artificial active immunization
F. Immunotherapy: Artificial passive immunity
15.8. Immunization: Methods of Manipulating Immunity for Therapeutic Purposes
A. Passive immunization
1. Immune serum globulin (ISG)
1-3
2. Specific immune globulin
3. Antisera and antitoxin
B. Artificial active immunity: Vaccination
1. Principles of vaccine preparation
a. Killed whole cells or inactivated viruses
b. Live, attenuated cells or viruses
c. Antigenic molecules derived from bacterial cells or viruses
d. Genetically engineered microbes or microbial antigens
C. Development of new vaccines
1. Artificial synthesis of vaccine antigens
2. Genetically engineered vaccines
a. Trojan Horse vaccines
b. DNA vaccines
D. Route of administration and side effects of vaccines
1. Adjuvant
2. Allergic reactions
3. Oral and injectable vaccines
E. To vaccinate: Why, whom, and when?
1. Herd immunity
2. Childhood immunizations
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