The Immune System
The human body must constantly defend
itself against unwanted intruders. Bacteria
and viruses as well as body cells that turn
cancerous can pose a huge threat … leading
to illness and potentially death.
The body’s immune system has evolved to
maintain homeostasis by fighting off
pathogens.
There are three lines of defence: two
nonspecific (does not distinguish between
microbes) and one specific (reacts in a
specialized way to different invaders).
(*Section 10.1)
The First Line of Defence
Pathogen:
disease-causing
organism
Leukocyte: white
blood cells that
may engulf
invading microbes
or produce
antibodies
Phagocytosis:
process by which
a white blood cell
engulfs and
chemically
destroys a
microbe
Macrophages:
phagocytic blood
cells found in
lymph nodes,
blood of bone
marrow, liver,
spleen
*All blood cells
are formed in the
bone marrow.
 The first line of defence is largely
physical. The skin provides a protective
barrier which often prevents bacteria and
viruses from penetrating. The skin has a chemical
defence in the form of acidic secretions that inhibit
growth of microbes.
 In the respiratory passage, cilia and mucus trap and
remove invading microbes and debris
 Lysozyme = an antimicrobial secretion present in
tears, saliva, mucous secretions, and saliva –
destroys the cell walls of bacteria.
The Second Line of Defence
 A second line of defence deals with any pathogen
that enters the body.
 Leukocytes = white blood cells
 There are two classes of leukocytes: granulocytes
which have granular cytoplasm and are produced in
bone marrow (eosinophils, basophils, and
neutrophils) and agranulocytes which do not have
granular cytoplasm and are produced in bone
marrow, but modified in lymph nodes (monocytes
and lymphocytes)
 See pg. 464 fig. 4 for summary of all blood cell
types
 Phagocytosis is the main mechanism in the second
line of defence.
Here are some ways the second line of defence can
work:
1. The Big-Eaters: A foreign particle penetrates the
skin. This causes monocytes to migrate from the
blood and into the tissue where they turn into
macrophages. The macrophages attach to the
surface of the invading microbe – they engulf and
destroy (phagocytosis).
2. The Pus-Makers: A chemical signal is given off by
damaged cells. This causes neutrophils to squeeze
out of capillaries and migrate towards damaged
tissue (= chemotaxis). Neutrophils engulf microbe
and release lysosomal enzymes that digest the
microbe and the leukocyte. The remaining chunks
of debris: protein, white blood cell bits, and digested
invader = pus.
3. The Inflammatory Response: Tissue damage can
trigger a localized nonspecific response resulting in
swelling, redness, heat and pain.
4. The System-Wide Response: Injured cells can emit
chemical signals into the circulatory system which
lead to an increased immune response. The
chemical signal can trigger production of more
phagocytic white blood cells; the hypothalamus can
also respond by cranking up the thermostat = fever.
Why do you think this unpleasant response would
help you out?
*Both the first and second lines of defence are
nonspecific.
Immune Response: Getting More Specific
(*Section 10.2)
The Lymphatic System: Circulatory Clean-up
 Some macrophages are wanderers that circulate
throughout the body and others take up permanent
residence in body tissues such as the brain, lungs,
and kidney. Macrophages that are fixed in the
lymphatic system (spleen, lymph nodes etc.) filter
out invaders that enter the blood.
 Pathogens, foreign cells and material, and debris
from the body’s tissues are filtered out from the
lymph (fluid found outside the capillaries) and the
lymph is returned to the circulatory system.
Detecting Invaders
Complement Proteins:
 The appearance of foreign organisms in the body
activates anti-microbial plasma proteins often called
complement proteins (about 20 types exist). These
proteins are normally present in the circulatory
system in inactive form, but are activated by marker
proteins on the invader.
 Complement proteins initiate an attack on cell
membranes of fungal or bacterial cells. There are
three groups of complement proteins that each stage
a different “attack”:
a) coat the invading cell – sealing it and
immobilizing it
b) punctures membrane – water enters and cell
can burst
c) attaches to invader and attracts leukocyte for
phagocytosis
* See page. 467 fig 2
T-cell:
Lymphocytes:
Lymphocyte that
 Lymphocytes produce antibodies
identifies and attacks
 Antibodies are special proteins
foreign substances
formed in the blood that inactivate or B-cell:
Lymphocyte that
destroy cells identified by a
produces antibodies
“matching” antigen marker. (This is
the ‘specific’ immune response.)
 All cells have antigen markers. The body does not
normally react to its own antigen markers, but the
cell wall of a bacterium or outer coat of a virus will
contain foreign antigens which can trigger the
specific immune response.
 There are two types of lymphocytes: T-cells
(produced in the bone marrow and stored in the
thymus) and B-cells (produced in the bone marrow)
 T-cells
Mission: seek out intruder and signal attack
T-cells recognize foreign antigen markers and pass this
info along to B-cells which can produce antibodies.
 B-cells
Mission: multiply and produce chemical weapons
Each B-cell produces a single type of antibody which is
displayed along the cell membrane. Some B-cells turn
into super antibody-producing plasma cells that can
produce as many as 2000 antibody molecules every
second.
Antigen-Antibody Reactions:
Antibodies are Y-shaped proteins engineered to target
foreign invaders. They are specific, meaning they are
only effective against a specific target pathogen. Each
antibody has a shape that is complementary to a
specific antigen on its target pathogen (like a lock and
key).
How do antibodies prevent a poison attack?
 Antibodies can prevent toxins from becoming
attached to cell receptor sites if they tie up the
poison by binding it. The shape of the toxin is
altered (now stuck to an antibody), so it can no
longer lock into the target cell receptor.
How do antibodies prevent viral attacks?
 Antibodies can lock onto antigen markers on the
viral coat, altering the shape of the virus and
preventing its entry into target cells (it no longer
matches receptors). The virus also becomes more
conspicuous as it increases in size (covered in
antibodies) and, therefore, becomes more prone to
macrophage attack!
*See pg. 468 fig. 4 for antibody-antigen pics
*Notice the constant and variable regions … you
may want to add this to your note here:
Recognizing Harmful Antigens
 When an pathogen is attacked by a macrophage, the
antigens found on the pathogen’s cell surface are
not destroyed; they are engulfed and pushed
towards the surface of the macrophage.
 The macrophage then associates with a T-cell
(helper T-cell). The T-cells reads the antigen shape
and does three things:
1. release lymphokine - a chemical that causes the
antibody-producing B-cells to divide into identical
clones.
2. send a second message to B-cells causing them to
produce the antibodies
3. activate killer T-cells: carry out search-anddestroy mission: find the intruder cell, puncture,
destroy!
*killer T-cells also destroy mutated cells (for example,
cancerous cells).
 Once the battle has been won, suppressor T-cells
signal the immune system to ‘shut down’.
Now that you know all this, can you guess how
immunosuppressant drugs like cyclosporin may work?
How does the T-cell process differ for a viral intruder?
*See pg. 469 fig. 469 for a good picture illustrating the
recognition of harmful antigens. Copy this important
diagram into your notes here.
Immune System Memory
 Memory B-cells are produced during an infection.
 Like helper T-cells, the memory B-cells hold an
imprint of the antigen(s) that characterize the
invader.
 Most T-cells and B-cells recruited to fight an
infection will die off within a few days, but the Bcells remain.
 B-cells make a person ‘immune’ to a disease. The
memory B-cells can act to quickly mobilize specific
antibody-producing B-cells to defeat the invading
pathogen before they become established.
*Make your own notes on organ transplants and stem cell research
(pg. 471)
You will also make your own notes (be sure to summarize!) on section
10.4 and 10.5.
Make sure to answer the following questions as you go …
10.3
What are allergies?
What is the anaphylactic reaction?
What is an autoimmune disease?
How is MS an autoimmune disease?
10.4
What is rabies?
Define virulent and contagious.
Summarize the historic event know as ‘The Black Death’
What is a vector for a disease?
Compare bacteria, viruses, and prions.
10.5
What is passive vs. active immunity?
How do vaccines work?
What is a hybridoma?
The Immune System
The human body must constantly defend itself against
unwanted intruders. ________________________________ as
well as body cells that turn cancerous can pose a huge
threat … leading to illness and potentially death.
The body’s __________________________ has evolved to
maintain homeostasis by fighting off ________________.
There are three lines of defence: two nonspecific (does not
distinguish between microbes) and one specific (reacts in a
specialized way to different invaders).
(*Section 10.1)
The First Line of Defence

The first line of defence is largely ___________. The skin
provides a protective barrier which often prevents
Pathogen:
disease-causing
organism
Leukocyte: white
blood cells that
may engulf
invading microbes
or produce
antibodies
Phagocytosis:
process by which
a white blood cell
engulfs and
chemically
destroys a
microbe
Macrophages:
phagocytic blood
cells found in
lymph nodes,
blood of bone
marrow, liver,
spleen
*All blood cells
are formed in the
bone marrow.
bacteria and viruses from penetrating. The skin has a
__________________________ in the form of __________ secretions that
inhibit growth of ________________.

In the respiratory passage, __________ and mucus trap and remove
___________________ and debris

_____________ = an antimicrobial secretion present in tears, saliva,
mucous secretions, and saliva – destroys the
________________________________.
The Second Line of Defence

A second line of defence deals with any pathogen that enters the body.

Leukocytes = _________________________________

There are _______ classes of leukocytes: __________________ which have
granular cytoplasm and are produced in bone marrow (eosinophils,
basophils, and neutrophils) and ___________________ which do not
have granular cytoplasm and are produced in _______________, but
modified in lymph nodes (monocytes and lymphocytes)

See pg. 464 fig. 4 for summary of all blood cell types

_____________________ is the main mechanism in the second line of
defence.
Here are some ways the second line of defence can work:
5. The Big-Eaters: A ________________________ penetrates the skin. This
causes ___________________ to migrate from the blood and into the
tissue where they turn into _________________. The macrophages
attach to the surface of the invading microbe – they
____________________________ (___________________________).
6. The Pus-Makers: A chemical signal is given off by _____________ cells.
This causes neutrophils to squeeze out of capillaries and migrate
towards damaged tissue (= _________________). _________________
engulf microbe and release lysosomal enzymes that digest the microbe
and the leukocyte. The remaining ___________ of debris: protein, white
_______________________ bits, and digested invader = pus.
7. The Inflammatory Response: Tissue damage can trigger a
_____________________ nonspecific response resulting in swelling,
redness, ________________________.
8. The System-Wide Response: Injured cells can emit
_________________________ into the circulatory system which lead to an
increased immune response. The chemical signal can trigger
production of more _________________ white blood cells; the
___________________________ can also respond by cranking up the
thermostat = ______________.
Why do you think this unpleasant response would help you out?
*Both the first and second lines of defence are nonspecific.
Immune Response: Getting More Specific
(*Section 10.2)
The Lymphatic System: Circulatory Clean-up

Some _________________ are ____________________ that circulate
throughout the body and others take up permanent residence in body
tissues such as the __________, lungs, and kidney. Macrophages that
are fixed in the ______________________ (spleen, lymph nodes etc.)
__________ out invaders that enter the blood.

Pathogens, foreign cells and material, and debris from the body’s
tissues are filtered out from the ____________(fluid found outside the
capillaries) and the lymph is returned to the
________________________________.
Detecting Invaders
Complement Proteins:

The appearance of ____________ organisms in the body activates antimicrobial ______________ proteins often called complement proteins
(about ____ types exist). These proteins are normally present in the
circulatory system in ______________ form, but are activated by
marker proteins on the invader.

Complement proteins initiate an attack on cell membranes of
_____________________________________. There are __________ groups of
complement proteins that each stage a different “____________”:
a) coat the invading cell – sealing it and ___________________ it
b) punctures membrane – water enters and cell can _______________
c) attaches to invader and attracts leukocyte
for ________________________
* See page. 467 fig 2
Lymphocytes:

Lymphocytes produce antibodies

Antibodies are special proteins formed in the
T-cell:
Lymphocyte that
identifies and attacks
foreign substances
B-cell:
Lymphocyte that
produces antibodies
blood that ___________________________ cells identified by a “matching”
__________ marker. (This is the ‘specific’ immune response.)

All cells have antigen markers. The body does not normally react to
its own antigen markers, but the cell wall of a _______________or outer
coat of a virus will contain foreign antigens which can trigger the
___________________________________ response.

There are two types of lymphocytes: ____________ (produced in the
bone marrow and stored in the _____________) and ______________
(produced in the ____________________)

T-cells
Mission: ___________________________________________________
T-cells recognize foreign antigen markers and pass this info along to Bcells which can produce ____________________________.

B-cells
Mission: multiply and produce ______________________________
Each B-cell produces a single type of antibody which is displayed along
the cell membrane. Some B-cells turn into ____________________________
______________________ that can produce as many as ___________ antibody
molecules every second.
Antigen-Antibody Reactions:
Antibodies are Y-shaped ______________ engineered to target foreign
invaders. They are specific, meaning they are only effective against a
specific __________________________. Each ___________________ has a
shape that is complementary to a specific antigen on its target pathogen
(__________________________________).
How do antibodies prevent a poison attack?

Antibodies can prevent toxins from becoming attached to
____________________ sites if they ______________________ by binding it.
The shape of the toxin is altered (now stuck to an antibody), so it can
no longer __________________ the target cell receptor.
How do antibodies prevent viral attacks?

Antibodies can lock onto ____________________________ on the viral
coat, altering the shape of the virus and preventing its entry into
target cells (it _______________________). The virus also becomes more
conspicuous as it increases in size (covered in antibodies) and,
therefore, becomes more prone to ______________ attack!
*See pg. 468 fig. 4 for antibody-antigen pics
*Notice the constant and variable regions … you may want to add
this to your note here:
Recognizing Harmful Antigens

When an pathogen is attacked by a macrophage, the antigens found
on the pathogen’s cell surface are not destroyed; they are
________________ and pushed towards the _____________ of the
macrophage.

The macrophage then associates with a T-cell (_________________). The
T-cells reads the antigen shape and does three things:
4. release _________________ - a chemical that causes the antibodyproducing B-cells to divide into identical ____________.
5. send a second message to ___________ causing them to produce the
_________________________
6. activate _____________________________: carry out search-anddestroy mission: find the intruder cell, puncture, destroy!
*killer T-cells also destroy mutated cells (for example, cancerous cells).

Once the battle has been won, _______________________ signal the
immune system to ‘shut down’.
Now that you know all this, can you guess how immunosuppressant
drugs like cyclosporin may work?
How does the T-cell process differ for a viral intruder?
*See pg. 469 fig. 469 for a good picture illustrating the recognition of
harmful antigens. Copy this important diagram into your notes here.
Immune System Memory

Memory B-cells are produced during an infection.

Like helper T-cells, the _______________________ hold an imprint of the
antigen(s) that _________________________ the invader.

Most T-cells and B-cells recruited to fight an infection will die off
within a few days, but the B-cells remain.

B-cells make a person ‘________________’ to a disease. The memory Bcells can act to quickly mobilize specific antibody-producing B-cells to
defeat the invading pathogen
_____________________________________________.
*Make your own notes on organ transplants and stem cell research
(pg. 471)
You will also make your own notes (be sure to summarize!) on section
10.4 and 10.5.
Make sure to answer the following questions as you go …
10.3
What are allergies?
What is the anaphylactic reaction?
What is an autoimmune disease?
How is MS an autoimmune disease?
10.4
What is rabies?
Define virulent and contagious.
Summarize the historic event know as ‘The Black Death’
What is a vector for a disease?
Compare bacteria, viruses, and prions.
10.5
What is passive vs. active immunity?
How do vaccines work?
What is a hybridoma?