Download Human Immune Responses

Human Immune Responses
www.user.gwdg.de/~hbruegg/ct/start.htm
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What is a pathogen?
• Any disease -producing
agent.
– Non-cellular agents
• Prions, viruses, viroids
http://kenyonfarrow.com/tag/african-americans/
– Cellular agents
• Bacteria, eukaryotes
http://www.bio.miami.edu/ecosummer/lectures/lec_
symbiosis.html
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A bit of history
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The Black Death killed about a third of
Europe’s population, between 1347 and
1351. But it was not until 1894 that the
pathogen (a bacterium) that caused the
plague was identified.
Scientists showed that fleas escaping
from dead infected rats carried the
bacterium to humans.
So, 550 years earlier, not knowing
anything about bacteria, the population
had no idea about the control and
prevention of the disease.
They used masks, closed all door and
windows to keep the wind out, attacked
foreigners and people of different
religions and whipped each other
believing it was God’s punishment.
http://bcm.bc.edu/issues/spring_2008/linden_lane/close-up.html
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A bit of history
• Before biologists such as Louis Pasteur
discovered bacteria and other pathogens people
had many strange ideas about preventing and
controlling diseases.
• Ignaz Semmelweis (a Hungarian doctor) insisted
that doctors washed their hands in a chlorine
solution before examining pregnant women.
This procedure greatly reduced “childbirth fever”
and the deaths of women in childbirth.
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A bit of history
• Malaria is a tropical disease that affects
millions of people worldwide. The term
malaria originates from Mediaeval Italian:
mala aria — “bad air“. It used to be called
marsh fever due to its association with
swamps and marshland.
• What’s the association?
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A bit of history
• The influenza pandemic of 1918 - 1919
(Spanish Flu)(H1N1) killed between 20 –
40 million people (12,000 in Australia).
• Today 250,000 to 500,000 die annually
worldwide. Most of these are people over
65.
• Today: Avian flu (H5N1) and Swine flu
(H1N1). Pandemic??
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What is an antigen?
A protein, toxin, or cellular or noncellular agents, to which the body
reacts by producing antibodies.
The exception being prions.
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Membrane receptors
• These are glycoproteins (MHCs) that
are unique to individuals.
• They allow the body’s immune
system to distinguish between SELF
and NON-SELF.
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Major Histocompatibility
Complex (MHC) proteins
• MHC proteins
occur on the
membranes of all
nucleated cells.
• These enable the
system to ensure
that “self” cells
are not destroyed
by the immune
system.
http://commons.wikimedia.org/wiki/File:TCR-MHC_bindings-tr.png
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MHC markers
• Class 1 markers are on the
membranes of all nucleated cells (not
RBCs)
• Class 2 markers are on membranes
of B cells, T cells and some
macrophages.
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Non-self
• Proteins or toxins (antigens) that have
NOT been produced by the body are
recognised as non-self.
• Such proteins that belong to pathogens
initiate a series of reactions – the immune
response – which are responsible for the
destruction and removal of the invader.
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Non-specific immunity
• First line of defence
–skin
–mucous membranes
–natural secretions
–natural flora
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Non-specific immunity
• Second line of defence
– phagocytes
– Natural Killer (NK) cells
– complement proteins
– interferon
– cytokines
– inflammation
– clotting
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Non-specific immunity
http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect23.htm
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Specific immunity
• Third line of defence
– B cells – humoral (antibody-mediated)
response
• Plasma cells
antibodies (immunoglobulins)
• memory B cells
– T cells – cell-mediated response
• helper T (CD4+) cells
• cytotoxic T (CD8+) cells
• memory T cells
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The lymphatic system
• The lymphatic system is
essential to both the
circulatory and immune
systems.
• The lymph nodes drain fluid
from most of our tissues.
They are an immunological
filter where the immune
responses mostly occur.
• Antigens are filtered out of
the lymph in the lymph node
before returning the lymph to
the circulation.
www.naturalhealthschool.com/8_4.html
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B and T cells
• B and T cells are lymphocytes.
• All lymphocytes are produced in
bone marrow.
• B cells mature in the bone
marrow.
• T cells mature in the thymus.
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B cells and antibodies
Each B cell contains multiple copies
of one kind of antibody as a surface
receptor for antigen.
The entire population of B cells has
the ability to specifically bind to
millions of different antigens.
When a B cell is matched with its
specific antigen two reactions are
triggered:
– plasma cell proliferation
• Antibody (monoclonal antibodies)
production
– memory B cell production
This process is called clonal
selection.
The production of antibodies by B
cells is called HUMORAL IMMUNE
RESPONSE.
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B plasma cells
Since antibodies are
proteins, B plasma
cells have a massive
protein manufacturing
infrastructure. Note
the:
– rough ER
– Golgi bodies
– mitochondria
http://cytochemistry.net/Cell-biology/
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Antibodies
• Antibodies are specific for
each different antigen.
• This specificity occurs at
the variable portion of the
antibody.
• The disulphide bonds
allow the chains to move
apart (like a hinge) to
enable them to capture
and accommodate the
antigen.
http://science.kukuchew.com/tag/immunoglobulin/
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Antibody response
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T cells – cell mediated response
• Cells that present an antigen on
their cell membranes are called
antigen presenting cells
(APCs).
• Macrophages engulf attacking
pathogens.
• Some of pathogens’ surface
proteins (antigen) are added to
macrophages’ membranes.
• Helper T (Th) cells recognise
these proteins (antigens) as
non-self as well as the
macrophages class 2 marker.
• Th cells secrete a protein,
cytokine, that stimulates the
cloning of B cells into plasma
cells and memory B cells. They
also stimulates the cloning of
cytotoxic (Tc) cells into active
Tc cells and memory T cells.
http://www.agen.ufl.edu/~chyn/age2062/lect/lect.htm
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T cells – cell mediated response
• Appropriate B cells then proliferate and
produce antibodies for that specific
antigen.
• Increased number of memory T cells are
then circulating to reduce time in finding
that pathogen.
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T cells – cell mediated response
• Cells that have been infected with a virus add
part of the viral protein coat (antigen) to their
membranes.
• Cytotoxic T (Tc) cells then recognise infected
cells by the presence of the added antigen and
the cells’ class 1 marker.
• Tc cells then release a protein that disrupt the
infected cells’ membranes (lysis) and the cells
then die before the viral particles have time to
replicate.
• This process also happens with cancer cells and
grafted cells.
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Immune response
http://www.biologycorner.com/
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http://www.biol.sc.edu/
Acquired immunity
• Active – when antibodies are produced by a
person
– natural
– induced
• Passive – when antibodies are received from an
external source
– natural
– induced
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Acquired immunity
• Natural active immunity
– when a person is infected by a pathogen and
the B cells produce antibodies. B and T
memory cells are also produced.
• Induced/artificial active immunity
– when a person is immunised against a
disease by vaccination. The body then
produces antibodies primary antibody
response.
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Acquired immunity
• Natural passive immunity – gives
immediate protection
– a foetus receives maternal antibodies across
the placenta.
• Induced passive immunity – also
immediate
– antibodies injected into a person.
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Plants and pathogens
• Mechanical barriers - similar to our skin
– cuticle (waxy layer) of leaves
– epidermal cells (including bark)
• Chemical barriers – similar to antibiotics
– many plants produce chemicals that can ward
off or kill pathogens.
• eg, the tobacco plant produces nicotine to kill
insects that eat its leaves.
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Control of diseases
• Quarantine
– strict controls at points of entry into Australia
to ensure exotic diseases and pests are not
allowed to enter.
• Departments of Health and Agriculture
– maintain statistics and, therefore, awareness
of changes of disease patterns in humans and
farm fauna and flora.
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Unit 3 Biology
Exams
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Examination time – 1½ hours
Contribution to study score –
33%
Approved materials and
equipment – pencil to use on
multiple-choice answer sheet.
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Students will be required to recall
facts, definitions, and examples;
explain biological concepts,
principles and processes; apply
understanding of these concepts to
unfamiliar situations; analyse
relationships; analyse and evaluate
experimental procedures; and
synthesise ideas.
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Total No. of marks: 75
Total No. of minutes: 90
Time per mark: 1 min.
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Examiners’ Report
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Most important in first few minutes
• Try and relax
– this will help you focus
• Read the exam paper cover sheet
– understand what the structure of the paper is and
what’s expected of you.
• Read through the paper
– you’ll start to feel more relaxed – you’ll know the
answers to some of the questions.
– you’ll probably find links between different questions
in different sections which may help you answer these
questions.
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When you start writing
• Write your VCAA number on the paper – in
numbers and words.
• Answer the questions that you know the
answers to first. You can start anywhere in
the paper. You’ll then feel more relaxed
and ready to tackle the rest of the paper.
• If you’re stuck on a MC question then
leave it for a while but mark the question
so as not to forget to come back to it..
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During the exam
• Keep an eye on the time!
– remember to try and keep to the pace of:
• ONE MARK = ONE MINUTE
• Multiple choice questions
– read each question carefully
– if you don’t know the answer try and eliminate
at least two of the distractors
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During the exam
• Short answer questions
– Keep answers short and to-the-point
– ‘1 mark’ usually means one point to make
– ‘2 marks’ – two points
• Near the end of the exam you should have
about 10 mins left. Have a look at your
answers but do NOT change any answers
on impulse. Think carefully!
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Overall
• ENJOY  doing the paper.
• Show the examiner what you
know and feel good about
doing it. You’ve worked hard
to get to that point.
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