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Applied Immunology
Aftab Jasir: European Centre for Disease Prevention and Control (ECDC)
European Public Health Microbiology training program (EUPHEM)Introductory course, Menorca,2012
Objectives
• Define basic components of immunology
• Describe important terms in immunology • Explain major applications of immunology
What is immunology? Immunology is a broad branch of biomedical
science that covers the study of all aspects of the immune system in all living organisms.
It deals with the physiological functioning of the immune system in states of both health and disease
What is the immune system?
The immune system is the ministry of defence of the human/animal body
Immunodeficiency and Immunosuppression
Immunodeficiencyis a state in which the immune system's ability to fight infectious disease is low or entirely absent.
Immunosuppression involves an act that reduces the activation or efficacy of the immune system. immunosuppression may occur as an adverse reaction to treatment of other conditions.
Major defence components of the human immune system
Cells Immunoglobulins
Overview of the immune system
Antigens (Ag)Large molecules, is anything that obtain the formation of a specific immune response (Anomy)
Ag determinants (epitopes) are the particular chemical groups on a molecule that are antigenic
Antibody(Ab)/immunoglobulin (Ig).A special group of soluble proteins that are produced in response to foreign antigens (substances)
Definitions/terminology
Antigen and antibody
5 classes of IGs1.IgM (first exposure, large, not passing placenta, huge amont)
2.IgG (secondary exposure, small, passing placenta)
1.IgD (proteins in the plasma membranes of mature B-lymphocytes, same time as IgM)
1.IgA (mucosal immunity, respiratory tract)
1. IgE (Allergy and parasites)
Haptens
Vaccine conjugate
Ministry of defence of the human body
Antibody Protection of the Host
Primary and secondary antibodies P: antibodies raised against an antigenic target of interest and are typically unconjugated. S: antibody that binds to primary antibodies or antibody fragments. They are typically labeled with probes that make them useful for detection,
Immune Precipitation
Antigen
Antibody
Agglutination
RBC
RBC
RBC
RBC
IgM Antibody IgM Antibody
IgG Antibody IgG Antibody
RBC
RBC RBC
RBC RBC
RBC RBC
Factors influencing immunogenicity
Class Switching
antibody titer
time
IgGIgG IgMIgM
Biological mechanism that changes a B cell's production of antibody from one class to another, for example, from IgM to IgG.
Four phases of the primary response
• lag phase where no antibody is detected• log phase in which the antibody titer rises
logarithmically• plateau phase during which the antibody titer
stabilizes• phase (decline) during which the antibody is
cleared or catabilized
Kinetics of the Ab ResponseT-dependent Ag; 1o Response
• Lag • Log
• Plateau
• Decline Ag
D a y s A f t e r I m m u n i z a t i o n
A b
T
i t
e r
LAG LOG DECLINEPLATEAU
Kinetics of the Ab ResponseT-dependent Ag; 2o Response
• Lag
• Log
• Plateau
• Decline
1o Ag 2o Ag
D a y s A f t e r I m m u n i z a t i o n
A b
T
i t
e r
Major practical applications of immunology
– Use of antiserum and vaccination to provide protection against disease.
– Diagnostic tool to detect disease.
– Epidemiological investigation of vaccine preventable diseases
My face is my fortune
Where are you going, my pretty maid?I’m going a-milking, sir, she said
May I go with you, my pretty maid?You’re kindly welcome, sir, she said
What is your father, my pretty maid?My father is a farmer, sir, she said
What is your fortune, my pretty maid?My face is my fortune, sir, she said
VariolationThe word ‘variolation’ comes from the Latin word ‘variola’ for
human smallpox.
Discovery of small pox vaccine
Edward Jenner 1780AD Blossom
Types of acquired immunity
Passive – receive Abs made by another 1. natural 2. artificial - γ globulin, hyperimmune serum
ArtificialNatural
Mode of delivery
Advantages Disadvantages
Immune suppressed/deficiency Long term immunity
Herd immunity
Not immediate
Risk of infection
Risk of contamination
Animal ???
Attenuated can revert to their pathogenic form
Advantages and Disadvantages of Active Immunization
Advantages and Disadvantages of Active Immunization
Advantages Disadvantages
serum sicknessimmediate protection
no long term protection
graft vs. host disease
risk of
hepatitis and HIV
Advantages and Disadvantages of Passive Immunization
Advantages and Disadvantages of Passive Immunization
Serology
A science that attempts to detect signs of infection in a patient’s serum such as Ab for a specific microbe
Serological tests based on Abs specifically binding to Ag – Ag of known identity will react with Ab in an
unknown serum sample.– Known Ab can be used to detect Ag in serum
Ag-Ab reactions are visible by clumps, precipitates, color changes or release of radioactivity.
The most effective tests have high specificity and sensitivity.
Enzyme (ELISA) Immunoassay
Antigen Antigen
anti-antigenanti-antigenantibody antibody
Enzyme Enzyme conjugated to conjugated to anti-Ig antibody anti-Ig antibody (“second (“second antibody”) antibody”)
Add Add substrate substrate
for enzymefor enzyme
a) The presence of a specific Ab b) Identification of microbes
Specificity, sensitivity, and cross reactivity
a) Specificity– Ab attaches with great
exact-ness to only one type of Ag.
b) Sensitivity – Ab can locate Ag, even
when it is greatly diluted.c) Cross reactivity
– the ability of an individual antibody combining site to react with more than one antigenic determinant or the ability of a population of antibody molecules to react with more than one antigen.
Examples of serological tests
1. Agglutination tests2. Precipitation tests3. Immunoelectrophoresis4. Western blot tests5. Complement fixation tests6. Immunofluorescence testing7. Immunoassays
Acute infection
Onset of symptoms
Primary infection
Incubation
Days Weeks Months Years
Onset of symptoms
Primary infection
Incubation
IgM
Days Weeks Months Years
Acute infection
Onset of symptoms
Primary infection
Incubation
IgM IgG
Days Weeks Months Years
Acute virus infection
Onset of symptom
s
Primary infection
Incubation
IgM IgG
Days Weeks Months Years
IgG avidity
Avidity = the sum of affinities between:
antibody
and
antigen
Acute virus infection
Onset of symptom
s
Primary infection
Incubation
IgM IgG
Persistence
IgG avidity
Days Weeks Months Years
Secondary infection or reactivation
Onset of symptoms
Primary infection
Viremia
IgM IgG
IgG avidity
Days Weeks Months Years
Secondary infection or reactivation
Time
1 2 1 2 1
IGtitter
IgM2
IgM1
IgG2
IgG1
1/40
1/64
1/800
Q fever
What should you have in mind!!!Tack home massage
Some times Ag x Ab based tests can results in wrong alarm of outbreak ( Salmonella)
Antigen variation is always a problem (Chlamydia, grouping of streptococci)
Cross-reactivity can give wrong information of an outbreak
Any unusual or unexpected results should be confirmed by genetic test
If possible use other methods than serology in an outbreak situation or combine with other methods