Download Disease

Introduction to The Immune
System
• Pin Ling (凌 斌), Ph.D.
ext 5632; [email protected]
• References:
1. Abbas, A, K. et.al, Cellular and Molecular
Immunology, 6th ed., 2007
2. Male D., J. Brostoff, D. B Roth, and I. Roitt
Immunology, 7th ed., 2006.
Keys toward Learning Immunology
•
Lectures => Deliver the key concepts of
Immunology.
•
Workbook => Apply the knowledge from
Immunology to the solution of clinical
problems.
•
Textbook reading => Help learn the
details and build up comprehensive
knowledge of immunology
Evaluation
For the Immunology Section:
• Examination => 70 %
• Attendance & Class performance
=> 30%
Outline
• The Origin of the Immune Concept
• Overview of Immunity to Microbes
• Features & Components of Innate &
Adaptive Immunity
• Summary & Question
The Origin of Immune Concept
1. The term “Immunity”
=> Latin word “Immunitas” => Protection from legal
prosecution (Roman senators)
Biological definition => Protection from infectious
diseases
2. The concept of immunity => existed in ancient Greek &
Chinese => the experienced view
Vaccination (also called Immunization)<=Vaccinia
3. The scientific view of immunity => Edward Jenner (1796)
Observation => Milkmaids generally get No smallpox
Hypothesis => Pus from vaccinia (cowpox)
=> Protect milkmaids from smallpox
Test => Inoculate materials from cowpox pus
=> Protect a young boy from smallpox
(Protective immunity)
Eradication of smallpox
Edward Jenner
Vaccines for common infectious diseases
Still no effective vaccines for many infectious microbes,
ex. HCV, HIV, …..etc
Outline
• The Origin of Immune Concept
• Overview of Immunity to Microbes
• Features & Components of Innate &
Adaptive Immunity
• Summary & Question
Key concepts about immunity-I
1. The immune system has evolved to protect us from the
invasion of pathogens.
Meanwhile, microbes have evolved to survive in the host.
2. Innate and adaptive immune responses (for vertebrates)
=> An integrated system of host defense
=> Cells & molecules function cooperatively
Antigen-presenting cells => Lymphocytes => Effector cells
3. Innate immunity is the older host defense system:
- Existed in both Invertebrates & Vertebrates
- Provides the initial defense against infections
- Activates and shapes adaptive immune responses
Key concepts about immunity-II
4. Adaptive immunity evolved later:
- Existed only in Vertebrates
- Provides the more potent and diverse defense against
infections
- Better
Develops understanding
as a response to infection
and adapts to the
of Immunology
infection

Help manipulate immune responses
 immune
Solve system
the medical
5. The
may fail =>problems
Immunodeficiency,
Hypersensitivity, & Autoimmune diseases.
6. Normal immune responses can be inconvenient in medical
cases, ex. organ transplantation
Overview of immune responses
Innate vs Adaptive immunity
The immune system has the ability to recognize
some self components:
-The Normal condition => prevent self-recognition
-The Pathological “ “ => occur self-recognition
Phagocytosis during innate immunity-I
Phagocytosis during innate immunity-II
Inflammation
=>A hallmark of innate immunity
=>Local accumulation of immune cells & molecules against
microbes
=>Function to eliminate infections but often cause tissue
damage & disease
Interaction between innate and
& adaptive immunity
1. Innate immunity
=> Ag presentation
(by infected cells)
2. Adaptive immunity
=> Ag recognition
(by T & B lymphocytes)
Overview of adaptive immune responses
Outline
• The Origin of Immune Concept
• Overview of Immunity to Microbes
• Features & Components of Innate
& Adaptive Immunity
• Summary & Question
Features of Adaptive immunity
Specificity, memory, and homeostasis
of adaptive immunity
Clonal expansion of lymphocytes
Types of adaptive
immunity
1. Humoral immunity
=> Molecules in body fluid,
ex. Antibody (Ab)
=> Key player => B cells
=> Target
extracellular
For
innate
immunity, it
microbes
& toxins
Cellular
components
for
2. Cell-mediated immunity
=> Key player => T cells =>
regulate other immune
cells
=> Target intracellular
microbes, ex. viruses,
bacteria
also includes Humoral &
immune defense
Active vs. Passive immunity
Active immunity => A host response to a microbe (Ag)
=> specific and long-term immune defense (memory)
Passive immunity => Adoptive transfer of Ab or lymphocytes
specific for a microbe (or Ag)
=> specific, instant but transient immune defense
Serum therapy => Humoral immunity & Passive immunity
Serum (Ab) from animals recovered from diphtheria
infection => Naïve animals => Resistant to diphtheria
infection
Key concepts in innate immunity
1. The innate immune system mainly recognizes common
structures shared by classes of microbes.
2. Microbial common structures => Pathogen-Associated
Molecular Patterns (PAMPs), ex. LPS, Peptidoglycan,
Microbial DNA & RNA.
3. Receptors that recognize PAMPs are called PatternRecognition Receptors (PRRs).
4. PRRs are encoded in germline DNA => limited Diversity
5. PRRs may also recognize components from injured or dead
host cells => Autoimmune diseases
Examples of PatternRecognition Receptors
(PRRs)
Toll-like Receptors
Locations of
Different PRRs
Body fluids
-Soluble PRRs
Cellular PRRs
- Cell surface
- Endosomes
- Cytosol
Soluble Pattern Recognition ReceptorsComplement activation pathways
Epithelial barriers prevent the
entry of microbes
Cellular components of the immune
system will be discussed extensively
in Lecture #2.
Failure of the immune system
Ineffective response
-Immunodeficiency
Overactive response
-Hypersensitivity
Auto-reactive response
-Autoimmunity
Outline
• The Origin of Immune Concept
• Overview of Immunity to Microbes
• Features & Components of Innate &
Adaptive Immunity
• Summary & Question
SUMMARY
1. Protective immunity against microbes is mediated by the
early response of innate immunity and the later response of
adaptive immunity.
2. Innate immune responses are initiated by recognition of
common microbial structures (PAMPs) by
- Provide the first line of host defense
- Activate and regulate the adaptive immunity
3. Adaptive immune responses are initiated by recognition of
foreign antigens by specific lymphocytes.
- Provide more potent, specific (Ag), & broad protection
- Develop immune memory for next exposure
- Feedback regulate innate immunity
Questions
1. Why is it necessary to vaccinate against tetanus only every 10
years, though antibodies against the toxoid disappear from the
circulation within a year?
2. Why is the vaccine against tetanus always effective, whereas
the vaccine against influenza protects on some occasions but not
others?
The End & Thank you