1. Immunology An Overview The only Principle of Immunology
Learn on your own:
Tolerance
Clinical Immunology
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Questions:
A: 1
B: 1 - 4
C: 1 - 3
D: both
E: 1
The only Principle of Immunology
for which there is no ambiguity:
Every Principle of Immunology has Ambiguity
Overview of Immune System

2. Respiratory tract cilia of innate defenses
Our immune defense has two branches
1. ‘Innate’ defenses
First lines of defense
Rapid response
Defend in a general way
-- not pathogen specific
Usually sufficient
2. ‘Acquired’ defenses
Last line of defense
Pathogen specific
Creates immunity
Slower onset
These systems closely interact
Respiratory tract cilia of innate defenses
Antibody molecule of Acquired defenses
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3. Four characteristics distinguish Acquired vs Innate responses
Recognition of pathogens
A few common “warning signals”
Millions of pathogen-specific antigens
Specificity of response
General response to pathogens
Response is to
specific antigens
Speed of response
Seconds to hours
Hours to days
Memory of encounter
None
Can yield
future immunity
B-cells
-- attack extracellular pathogens; toxic molecules
Upon activation release AG-specific antibodies
T-cells
1) hornmonally regulate immune system
2) attack intracellular pathogens
-- kill cells
T-cells as “MHC restricted”
-- only bind to peptide fragments “presented” by other cells
CD4 cells: upon activation secrete cytokines
-- needed for activation of B-cells and T-cells
CD8 cells: upon activation attack infected body cells
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4. Overview of Immune System
What are the types of
Innate Immunity?
I. Non-induced mechanisms
“Barriers to infection”
-- 1st line of defense
Anatomical
Mechanical
Cilia and mucus
Skin wounding
Overview of Immune System

5. Overview of Immune System
Innate Immunity…
II. Induced mechanisms
Physiological, e.g., fever
Cellular , e.g., phagocytosis
Enzymatic, e.g., complement
Receptor-mediated
Broadly specific
-- recognize “danger signals”
-- PAMPs
Responses
phagocytosis
pathogen killing
antigen presentation
cytokine production
Anatomical
Skin & epithelial layers: a formidable barriers to infection
-- tough and impervious
-- look how readily infection sets in following wound
Ciliated epithelial cells: (eg. of trachea) serve same purpose
Body fluids
-- Saliva, tears and mucous secretions
-- wash away potential invaders before colonization can begin
Physiological
Body temperature alone makes body unsuitable for certain pathogens
-- ANTHRAX used to be a common disease of farm animals
-- chickens have an innate immunity to bacterium
-- due to higher body temperature
pH of stomach & female reproductive tract
-- lethal to many common pathogens
Cellular
Phagocytic cells (macrophages, neutrophils)
granulocytes, etc
Chemical/enzymatic
-- bile, H2O2, free radicales
-- lysozyme, proteases, other enzymes
Overview of Immune System

6. Microbes can cause infections outside or inside of cells
Always Intracellular: Viruses
Intra- or extra- cellular: Bacteria
Usually extracellular:
Fungi, Protozoa, worms
Adenovirus infected cell
Listeria
infected
cell
Listeria
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7. Humoral There are two “arms” of the Acquired Immune System?
Attack extracellular
pathogen and toxins
B-cells > antibodies
Cell-mediated
1) Attack infected body cells
& cancerous cells
T-killer cells
T-cells
T-helper cells
2) Hormonal regulation (Cytokines)
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8. Antibodies are produced by the Humoral arm of the acquired immune system
Involves B-cells
Attack pathogens outside of cells
Have B-cell receptors (BCR)
-- a type of antibody
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9. T-cells possess T-cell Receptors
Similar to Antibodies
-- antigen-specific
-- one type per cell
-- created by gene rearrangements
However,
-- less specific than antibodies
-- less diverse (fewer types)
-- never are released
-- only bind to antigens on MHC
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10. T-helper cells and T-killer cells bind to different types of MHC
Killer-T cells
-- bind to AG on MHC-I
-- attack infected &
cancerous cells
Helper-T cells
-- bind to AG on MHC-II
-- hormonally regulates
immune response
Macrophages,
Dendritic cells, B-cells
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11. Overview of Immune System
What are the two types of antigen-presenting cells?
“Professional” AG-presenting cells “Non-professional”
-- via MHC-I or MHC-II -- All nucleated body cells
-- can present antigen to TH and TC cells -- only present to Cytotoxic T-cells
Examples -- only via MHC-I
-- dendritic cells & -- response is cell destruction
-- macrophages
-- B-cells
-- (other IM cells)
Overview of Immune System

12. Overview of Immune System
Upon activation Naïve immune cells become Effector cells
B-cells become:
Plasma cells
TH cells become:
TH effector cells
-- activate other cells
Tc cells become:
Cytotoxic lymphocytes
(CTLs)
Overview of Immune System

13. Overview of Immune System
What happens when lymphocytes are activated?
“Clonal Selection”
Antigen recognition
Cell activation
Memory cells
Immunological memory
Primary vs Secondary responses
Overview of Immune System

14. Overview of Immune System
How do immune cells communicate?
Extensive cell-cell contact
Membrane protein interaction
Immune synapse
Hormonal exchange
Cytokines
Interleukins
Interferons
Chemokines
etc
Endocrine
Paracrine
Autocrine
Overview of Immune System