Applied Immunology

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Applied Immunology
Aftab Jasir, European Centre for Disease
Prevention and Control (ECDC) European Public
Health Microbiology training program (EUPHEM)
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Objectives
Define basic components of immune system Define
important terms in immunology Explain major
applications of immunology
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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

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What is the immune system?
The immune system is the ministry of defence of
the human/animal body
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Major defence components of the human immune
system
Immunoglobulins
Cells
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Definitions/terminology
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)
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Antigen and antibody
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Haptens
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5 classes of IGs a. IgG (secondary exposure,
small, passing placenta) b. IgM (first
exposure, large, not passing placenta, huge
amont) c. IgA (mucosal immunity, respiratory
tract) d. IgE (Allergy and parasites) e.
IgD (proteins in the plasma membranes of mature
B-lymphocytes, same time as IgM)
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Ministry of defence of the human body
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Factors influencing immunogenicity
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Immunogenicity contribution of biological system

• Genetics
• Species
• Individual
• Responders vs Non-responders
• Age

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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

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My face is my fortune
Where are you going, my pretty maid?Im going
a-milking, sir, she said May I go with you, my
pretty maid?Youre 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
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Variolation

• The word variolation comes from the Latin word
  variola for human smallpox.

source Claire JP Boog
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Discovery of small pox vaccine
Blossom
Edward Jenner 1780AD
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Edward JennerAmong patients awaiting small pox
vaccination
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Types of acquired immunity
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Passive receive Abs made by another 1.
natural 2. artificial - ? globulin,
hyperimmune serum
Artificial
Natural
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Mode of delivery
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Advantages and Disadvantages of Active
Immunization

• Not immediate

• Immune suppressed/deficiency

• Long term immunity
• Herd immunity

• Risk of infection
• Risk of contamination
• Animal ???
• Attenuated can revert to their pathogenic form

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Advantages and Disadvantages of Passive
Immunization

• no long term protection

• serum sickness

• immediate protection

• risk of hepatitis and AIDS

• graft vs. host disease

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Serology

• A science that attempts to detect signs of
  infection in a patients 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.

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a) The presence of a specific Ab b)
Identification of microbes
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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.

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Examples of serological tests

• Agglutination tests
• Precipitation tests
• Immunoelectrophoresis
• Western blot tests
• Complement fixation tests
• Immunofluorescence testing
• Immunoassays

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ELISA

• Enzyme-linked immunosorbent assay (ELISA), also
  known as an enzyme immunoassay (EIA),
• is a biochemical technique
• used mainly in immunology to detect the presence
  of an antibody or an antigen in a sample.
• has been used as a diagnostic tool in medicine
  as well as a quality control check in various
  industries.

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ELISA

• an unknown amount of antigen is affixed to a
  surface
• a specific antibody is applied over the surface
  that binds to the antigen
• antibody is linked to an enzyme
• a substance is added that the enzyme can convert
  to some detectable signal, most commonly a colour
  change in a chemical substrate

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Agglutination tests

• Ab cross-links whole cell Ag, forming complexes
  that settle out and from visible clumps in the
  test chamber
• Purpose of agglutination testing
• Qualitative testing
• blood typing, some bacterial viral diseases.
• Quantitative testing
• Used to detect titer (maxium dilution that will
  still give visible agglutination)
• Difference between agglutination and
  precipitation?
• Agglutination gt clumping together of insoluble
  molecules
• Precipitation gt aggregation of soluble
  molecules

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Importance for epidemiologistEx1

• 2005, outbreak of Salmonella like illness in
  Skåne ) Sothern Sweden, in the same time report
  from Denmark of Salmonella enterica.
• Diagnostic of pathogen in Sweden was not
  successful
• Many of patients had common sort of relation
  (eating in the same restaurant, buying meat from
  same market or meat imported from Denmark)
• Media reported a new sort of (unknown) infection
• Speculation of new type of Salmonella among
  doctors
• 6 days later Salmonella enterica was detected in
  the main lab in Skåne
• What was wrong?

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Ex2

• 1999, Outbreak of scarlatina like (Scarlet fever)
  in 2 daycares in Lund, Sweden
• 28 Children were diagnosed by symptoms
• Two teacher, one working in both daycares, one
  developed STSS
• No Lab confirmation of Group A streptococci
• Microscopy showed gram positive chained bacteria
• One weak later two children were confirmed by lab
  results having Group A streptococci
• What was wrong know??

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Diagnostic of viral infections
Prof. Matthias Niedrig, RKI
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What should you have in mind!!!

• 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