viral pathogenesis - scholar.cu.edu.eg adaptive (acquired) immunity. •show the evidence of...

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Introduction to immunology:

It’s a dangerous matter.

VIR-3178

Ausama A. YousifDVM, MSc, PhD

Professor of Virology

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Disclaimer

• The classical view slides were privided by Dr. Nancy L.

Haigwood, Ph.D. [haigwood@u.washington.edu]

• Additional resources were added from a lecture by Marie

Lipoldová. Institute of Molecular Genetics. Academy of

Sciences of the Czech Republic. www.img.cas.cz/mci/

• I have chosen to present the lecture as is, with added

information bearing both virology logos. This is to get a

sense of the current paradigm in immunology.

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Learning objectives

• Overview the components of the immune systems.

• Describe the names and functions of the key players of adaptive (Acquired) immunity.

• Show the evidence of specificity, memory and self limitation.

• Show the immunological goal of vaccination and how to improve the animal’s chances of surviving infection with a virulent virus.

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Is the immune system

Functional or Anatomical?

Just protection against pathogens? NO.

• Elimination of tissues and cells that have been damaged, infected or killed.

• DOES THE IMMUNE SYSTEM RECOGNIZE ANTIGENS THE SAME WAY IN THE DIFFERENT COMPARMENTS OF THE BODY?

• Remember this question. We will get back to it later

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The Classical View

Innate

Immunity

Acquired

Immunity

Nancy L. Haigwood, Ph.D.

haigwood@u.washington.edu

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The Classical View of how

the adaptive immune system works

• Discrimination between pathogens/self.• Antigen specificity.• Diversity of responses. • Self-limiting.• Produces immunologic memory.

• WHY DON’T IMMUNE CELLS RECOGNIZE SELF ANTIGENS?!!

• This is a trick question.

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Post-infection immune responses

Viral

titers CTLAntibody

Days post-infection

7 14 28 350

Illness

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Specificity, memory, self-limitation

X-s

pe

cifc

An

tibo

dy tite

rs

Weeks

Antigen

X

Antigen

X

2 4 6 8 10 12

IgM response

IgG response

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The Classical View of how

the adaptive immune system works

• Discrimination between pathogens/self.

• Antigen specificity.

• Diversity of responses.

• Self-limiting.

• Produces immunologic memory.

• WHY DON’T IMMUNE CELLS RECOGNIZE SELF ANTIGENS?!!

• Review selection in the thymus.

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Goal of vaccination

Reduction of Illness Vs Reduction of Replication

CTLAntibody

Vaccine Infection

CTLAntibody

Illness

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In order to achieve this goal we

need to think a little bit more

about the specifics of the adaptive

immune response.

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Exogenous (MHCII) and Endogenous (MHCI) Pathways of Antigen Presentation

HS

P 7

0

This is not the

complete pictureWhy does the immune system recognize self tissue that has been

damaged (like testicular tissue for instance, or the endocardium during

certain bacterial infections)?

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BIC 2005 - Introduction to Artificial Immune Systems - Dr. Leandro Nunes de Castro14

The Immune System (XVII)

◼ Danger Theory

after Matzinger, 1994

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DC activation and

Th activation and polarization

Nature Reviews Immunology 3, 984-993 (December 2003)

If the immune system works so well

how come the virus maintains itself

in immunocompetent populations?

Refer to the answers we discussed in

Advanced General Virology

Last semester

Email me if you have questions

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Don’t you think that this kind of immune

evasion will also influence the outcome of

infection of vaccinated animals?

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Take home messages1. The immune system responds to danger signals; even if it is

associated with self antigens.

2. The nature of the antigen and cytokine environment determine the

immune system polarization towards Th1- or Th2-type responses.

3. Exposure to antigen in the correct context results in the

development of immunological memory.

4. The immune system responds differently to antigens in different

compartments.

5. Viruses are able to evade host cell immunity by manipulation of

antigen presentation or cell signaling pathways.

6. Successful protection against viral infection can only work if the

immune response worked in the correct time and location, with the

correct type and level, and if the animal has a correct feed back

mechanism. (TTLLF)

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• WHY DOES THE IMMUNE SYSTEM RECOGNIZE ANTIGENS DIFFERENTLY IN THE DIFFERENT COMPARTMENTS OF THE BODY?

TAKE HOME QUESTION