1. BASIC PRINCIPLES OF ADAPTIVE IMMUNITY AND IMMUNIZATION
CHAPTER 17
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2. Adaptive (Acquired) Immunity
Natural
Artificial
Active
Passive
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3. Antigen Characteristics
Antigens
Foreign molecules
Epitopes
Molecular determinants on Ag
May be multiple on one Ag
Haptens
Small Ag
Sometimes cause allergies
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4. Immune System Compartments
B lymphocytes
10% of circulating lymphocytes
Antibody production
Humoral Immune compartment
T lymphocytes
75% of circulating lymphocytes
Cell-mediated immune compartment
2 major sub-types
Helper T cells
Cytotoxic T cells
Natural Killer cells
No clonal stimulation
Cause lysis and apoptosis of pathogenic cells
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5. Protection and Development
Humoral Immunity
Antibody production by B cells
Bacteria, toxins and viruses
Cell-mediated Immunity
Cell lysis, apoptosis
Foreign eukaryotic cells
Virally infected
Fungal, protozoan, helminthic
Cancer
Transplanted organs
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6. Immune system Properties
Self versus Non-self Recognition
Maturation leads to Clonal Deletion
Defects = autoimmune disease
Specificity
Random gene rearrangements create potential binding sites for antigens
Some cross-reactivity
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7. Immune System Properties
Diversity
Over 1 billion antigen binding sites are possible
Memory
Sub-populations of stimulated lymphocytes remain in lymph nodes to provide a faster, larger response on second antigen encounter
Basis of “Immunity” or the anamnestic (secondary/ memory) response
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8. Humoral Immunity B lymphocyte binds Ag
Bound Ag is engulfed and fragmented within the B cell
Ag fragments + Major Histocompatibility Complex Type II (MHC II) proteins together = presented or “processed” antigen
Triggers Interleukin 2 (IL-2) production from T cells
This stimulates B cells further and creates memory cells
Known as T-dependent Ag, usually proteins
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9. Antibody Structure Heavy/Light Chains Variable/Constant Regions
Antigen Binding Site
Disulfide Bridges (Bonds)
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10. Immunoglobulin (Ig) Classes
Ig G
Main serum Ab
Produced in 2o response
Transplacental
Activates complement and phagocytes
IgA
Secreted
Abundant in colostrum
Protected by secretory component
Activates complement
Ig M
Large molecules
First to be produced
Indicative of recent infection
Ig E (reagin)
Bound to mast cells and basophils
Triggers allergic responses
Ig D
Not well understood
May trigger allergic responses
High levels in autoimmune disease

11. Immune Response Types Primary Response IgM initially
IgG detectible in 2-3 weeks
Levels may drop after initial exposure
Memory cells persist
Secondary / Memory Response
Much larger response of IgG
Protection against invading microbes and toxins
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13. Antigen Types T-independent No helper T cells
No memory cells are created
Only IgM
Carbohydrate Ag, often capsular on bacteria
T-dependent
Needs helper T cells
Creates memory B cells
IgM and IgG
Protein Ag
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14. Antibody Effects Agglutination Target count reduction
Complement mediated effects
FC fragment (Constant region) activates complement
Cytolysis
Opsonization
Increased inflammation
Neutralization
Viral and bacterial binding sites for host cell attachment are blocked
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15. Monoclonal Antibodies
Multiple myeloma cells + normal lymphocytes
Hybrid cells
Immortal in large-scale cell culture
Specific Ab producers
Uses
Diagnostic
Anticancer
Anti-tissue rejection
Allergies to mouse proteins are a challenge
Humanized Mabs
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16. Cell Mediated Immunity
Processed antigens presented alongside MHC proteins
TH cells are activated by Ag + MHC II, on antigen presenting dendritic cells, B cells or macrophages
TC cells are activated by Ag + MHC I , usually on infected cells with intracellular virus or bacteria, transformed cells or transplant cells
Memory T cells can form
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17. TH Cell activity Helper T cells (TH) release lymphokines IL-2
stimulates Ab production
Activates TC cells
Gamma IFN
Co-ordinates inflammatory response
Antiviral and anti-tumor
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18. Tc Cell activity Activation Ag + MHC I Cell lysis Perforins
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19. NK Cells – Innate Immunity
Natural Killer cells
Produce Perforin proteins
Lyse tumor and bacterially infected cells
Induce apoptosis
Activated by lack of MHC Class I proteins on cell membranes, no clonal stimulation
NK cell video clip
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20. Mucosal Immune System MALT Mucosal associated lymphoid tissue GALT
Gut associated lymphoid tissue
M cells
Mucosal cells that transfer antigens to antigen presenting lymphocytes
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21. Factors Modifying Immune System Health
Genetic factors
Age
Season
Diet
Exercise
Sleep deprivation
Pregnancy
Trauma
Environment
Medications
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22. Immunization Types ACTIVE PASSIVE Ag administration
Toxoid or microbial structural molecule
Whole cell killed
Attenuated
Subunit
Recombinant DNA vaccines
Live vaccines provide longer protection
Route of administration affects protection level
Ab administration
Immune serum globulin
Antitoxins
Antivenins
Temporary, protection declines
Will affect the course of a disease
Allergic reactions are commonest drawback
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23. Ideal Vaccine Qualities
Protective
Safe
Sustained effects
Generate active immunity
Stable shelf life
Affordable
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24. Immunity to Different Pathogens
Bacteria
B cell Ab production
Viruses
T cell attack of virally infected cells
Fungi
T cell attack of fungi
Protozoa/Helminths
T cell attack of protozoa and worms
Eosinophil Responses
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