Transcript 11.1 HL Immune System Part 1

The Immune System & Response
to Invasion
•IB Learning Objective
•Describe the process of blood clotting
Copyright Pearson Prentice Hall
Blood Cells
Platelets and Blood Clotting
–The body has an internal mechanism to
slow bleeding and begin healing.
–Bleeding stops because blood has the
ability to form a clot.
–Blood clotting is made possible by plasma
proteins and platelets.
Step 1 in blood clotting
When we cut ourselves, we
cut small blood vessels.
When this happens are body
forms a clot.
A clot stops us from losing
blood and from a foreign
pathogen from entering out
body.
Step 1 in blood clotting
A wound triggers a cascade
of events by which a blood
clot is formed.
First platelets collect at the
site of the wound.
Platelets are small disc
shaped cell fragments
Platelets do not contain a
nucleus
Step 2 in blood clotting
Platelets build up at wound and seal off small
breaks in blood vessels
Step 3 in blood clotting
Step 4 in blood clotting
Fibrin proteins form a mesh
of fibres which traps red
blood cells. These dry and
become a scab which closes
the wound.
Clotting is the mechanism that prevents and
blood loss from broken blood vessels.
a) Platelets or damaged cells release a
group of proteins called clotting factors.
These clotting factors are released into
the plasma a wound site.
b) Clotting factors activate the enzyme
Thrombin from its inactive form
prothrombin
c) Thrombin turns the soluble plasma
protein fibrinogen into its insoluble
fibrous form Fibrin.
d) Fibrin binds together platelets and
blood cells to form a solid 'plug' for the4
wound. This plug is called a clot.
Leukocytes
• Circulate in many parts of our body. Below is
a list of parts of the body where you might
find leukocytes
– Blood vessels (veins, arteries, capillaries)
– Walls of tissues
– Lymph vessels and nodes
– Organs (especially liver & lungs)
IB Assessment Statement
• Outline the principle of challenge and
response, clonal selection and memory cells
as the basis of immunity.
White Blood Cells
• Our main defence from disease once it is
inside of our bodies is are white blood cells,
also called leukocytes.
Lymphocytes
• Specialized leucocytes called lymphocytes are
responsible for the immune response in our
bodies.
• Lymphocytes have the ability to recognize our
‘self’(our own body cells and proteins) and
can recognize ‘non-self,’ antigens (foreign
molecules or microorganism (bacteria, virus
etc……)
How do are Lymphocytes recognize ‘self’
(own body cells & proteins)
• Cells are identified by specific molecules lodged in
the outer surface of the cell (plasma) membrane.
• These molecules are called glycoproteins ( a
molecule that contains a carbohydrate and a protein)
glycoproteins
• Glycoproteins that identify cells are known as
the Major Histocompatability Complex (MHC)
• There are genes on our 6th chromosome that
code for our MHC. Thus, our MHC is
genetically determined.
• Each of us as a unique MHC on our cells
membrane.
Antigen Receptor
• Our Lymphocytes of our immune system have
an antigen receptor that recognizes our own
MHC antigen and differentiates these from
foreign antigens detected in the body.
Immunocompetence
• All lymphocytes develop in bone marrow, they
develop Immunocompetence.
• Immunocompetence means they have the
ability to recognize one specific antigen ( the
bodies antigen or MHC).
• Immunocompetent lymphocytes are stored in
the lymph nodes.
Types of Lymphocytes
•Two distinct types of Lymphocytes
1. B-Lymphocytes (B-Cells)– secrete antibodies
2. T-lymphocytes (T-Cells) – attack infected cells.
What happens when an Antigen
Invades the body?
• An invading will eventually
reach the tissue and
lymph fluid and encounter
a lymphocyte with an
antigen receptor.
• The lymphocytes will respond by rapidly
dividing and growing, leading to a vast
numbers of cells producing antibodies
• Antibodies eventually overcome and dispose
of the source of foreign antigens.
• Each immune response event produces
memory cells.
• Memory cells survive in the body(mostly in
the lymph nodes), for years after the event.
• If the same antigen returns, the body is able
to respond quickly, using these memory cells.
• We then say that we have immunity to that
pathogen.
Steps of Antibody Production
Introduction
• B-Cells are the lymphocytes that produce
Antibodies.
• If a B-Cells recognizes and binds to a specific
Antigen, the B-Cells proliferate into many cells
called plasma cells.
• Plasma Cells secret antibodies into the blood
stream.
• These process is called the Humoral
Immunity.
IB Assessment Statement
• Define active and passive immunity.
Types of Immunity
• There are two types of immunity
1. Passive Immunity
2. Active Immunity
Passive Immunity
• Passive immunity is due to the acquisition of
antibodies from the mother via the placenta
and milk.
• Also antibodies can be received by injections.
Active Immunity
• Active immunity is due to the production of
antibodies by the organism, after the body’s
defence have been exposed to antigens.
Passive vs. Active
• Active Immunity –
• Passive Immunity – is
develops when a person
acquired when
is exposed to
antibodies are
microorganisms or
transferred from one
foreign substances and
person to another.
the person’s immune
• The recipients do not
system responds.
make the antibodies
themselves
Review
Active & Passive Immunity
• Is this active or passive immunity?
– Antigen enters body….the body produces
antibodies to neutralize antigen.
– NATURALLY ACQUIRED --- ACTIVE IMMUNITY
Review
Active & Passive Immunity
• Is this active or passive immunity?
– Antibodies passes from mother to fetus during
pregnancy
– NATURALLY ACQUIRED --- PASSIVE IMMUNITY
Review
Active & Passive Immunity
• Is this active or passive immunity?
– Weakened or dead fragments of a microbe are
injected into the body….the body produces
antibodies to neutralize microbe
– Artificially ACQUIRED --- Active IMMUNITY
Review
Active & Passive Immunity
• Is this active or passive immunity?
– Antibodies in a serum (i.e. antivenom used to
treat snake bites) are introduced to the body……
– Artificially ACQUIRED --- PASSIVE IMMUNITY
IB Assessment Statement
Address the Learning Objective Below:
• Explain antibody production
When an Infection Occurs
The antigens of a pathogen bind to the antibodies
in the surface membrane of a lymphocyte…
…This activates the lymphocyte.
The active lymphocyte divides by mitosis to
produce a clone of many identical cells
MITOSIS
The clone of cells
starts to produce large
quantities of the
same antibody…
… the same antibody
needed to defend
against the pathogen!
Most microbes have more
than one antigen on their
surface, so…
…they stimulate more than
one type of lymphocyte…
…resulting in the production
of many different
antibodies.
These are called
polyclonal antibodies.
Antibody Production: The Primary Response
Step 1: Antigen Presentation
Antigen
Macrophage
Macrophages take in antigen
by endocytosis
The macrophage processes the
antigen and attaches it to a
membrane protein called a
MHC protein
The MHC protein is moved to the
cell surface membrane by
exocytosis so that the antigen
is displayed on its surface.
MHC protein
Step 2: Activation of Helper T-cell receptor
Helper T-cells have receptors on
their cell surface membranes which
can bind to antigens presented by
macrophages.
Helper T-cell
Helper T-cell binds to macrophage
presenting the antigen
Macrophage sends a signal to activate the helper T-cell
Step 3: Activation of B-lymphocytes
B-cells have antibodies in their cell surface
membranes
Antigens bind to the antibodies in the surface
membranes of B-cells
Antigen
Inactive B-cell
Antibody
An activated helper T-cell with
receptors for the same antigen
binds to the B-cell
SIGNAL
The helper T-cell sends a signal to the B-cell,
activating the B-cell.
Step 4: Proliferation
The activated B-cell starts to
divide by mitosis to form a clone of
plasma cells.
Plasma cells are activated B-cells
with a very extensive network of
rough endoplasmic reticulum.
Plasma cells synthesis large
amounts of antibody, which they
excrete by exocytosis.
The Secondary Response: Memory Cells
• If an antigen invades your body a second time, a
much faster response occurs which produces
much larger quantity of the required antibody.
•When activated B-cells are dividing during the
primary response, some cells stop dividing and
secreting antibody and become memory cells.
• Large numbers of memory cells remain in the
body for a long time…
• …they are capable of producing large amounts of
antibody very quickly when stimulated.
Antigen
Antigen
Activate
B-cell
Clone
Memory
Cell
Activate
Helper
T-cell
Antibody Production:
Summary
Plasma Cell
Macrophage
Antibodies