Download Ch. 43 - Immune System

Ch. 43 – the immune system
Essential Knoweldge 2.D.4 (a-b)
Overview
A virus uses the
machinery of your
cells to make more
copies of itself, until it
destroys the cell;
when that happens,
the cell bursts and
releases all the new
viruses into your body
to repeat the process
 Without the immune
system, we’d be in big
trouble.

Overview
There are 2 basic types of
immunity; innate and acquired
 Innate immunity


Is present before any exposure
to pathogens and is effective
from the time of birth (passed on
from mother through the
placenta or in breast milk)
 Involves nonspecific responses
to pathogens (like a fever)

Acquired immunity, also
called adaptive immunity

Develops only after exposure to
inducing agents such as
microbes, toxins, or other
foreign substances
 Involves a very specific
response to pathogens
Figure 43.1
3 m
How Immunity Works - Skin
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This is the first layer of
defense
Creates a barrier
Has a low pH (which makes it
hard for bacteria to live there)
Chemicals on the surface of
our skin disrupt certain
viruses
Bacteria (normal flora which
just lives there) crowd out our
skin which makes it hard for
other substances to enter
Certain cells of the mucous
membranes produce mucus

A viscous fluid that traps
microbes and other particles
Skin cont.
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If you get a cut, then there is a breach
in your first defense
Anitgens – any foreign invader in your
body
Internal cellular defenses
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Phagocytes, types of white blood cells
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Ingest invading microorganisms
Initiate the inflammatory response
Inflammation occurs (chemicals are
released that causes our body to
respond)
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Depend mainly on phagocytosis (cell
eating)
For example – acne (an infection in the
pores of your skin)– bacteria are living
and eating under our skin
Macrophages (a specific type of
phagocyte found throughout your
body) enter and eat the invaders
(called antigens); this causes
swelling. Macrophages secrete
lysosomes into the antigen to destroy
it; problem – it will attack anything not
us, including organ transplants
Specific immune response
Specific immune responses
mean that we have generated
antibodies for a specific virus,
so we won’t get the same
cold twice
 Antigens (what’s invading the
cell) have specific proteins on
their surfaces
 To fight them, we have
structures called antibodies
(proteins produced by our
bodies)
 They have very specific
shapes that will allow them to
connect to the antigen; this
helps the macrophages find
them, and it also makes it
harder for the antigens to do
their job

Specific Immune Responses
Cont. – B lymphocytes
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B Lymphocytes are 1 type of
white blood cells or phagocytes
(attack viruses in our bodies)
Made in bone marrow
Create a humoral response
(means, “in the fluid” or in the
“humors” – like blood, lymph
material, insterstitial fluid)
Produce antibodies
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A naïve B cell senses the shape of
the antigen, sends out a chemical
message, and the B lymphocytes
produce the antibodies specific for
that antigen
Memory B cells are then created
to help give us immunity for the
rest of our lives
Specific Immune Response cont T Lymphocytes
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T Lymphocytes target and
kill the cells that are
already infected
(responsible for what’s
called a cell-mediated
response)
Created in the thymus (a
gland on top of our heart;
this is where they get the
“T” from)
Create Killer T Cells or
Cytotoxic T Cells (a type of
T lymphocytes) which
target cells that are
infected, docks next to
them, and kills them
Causes cell death
Helper T Cells
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You have an antigen that is eaten by a
macrophage, which chops up the
antigen and produces pieces of it on
it’s surface using a chemical called
MHC2; you then get a Helper T cell
(another type of T Lymphocyte) which
docks on the macrophage and senses
the shape of that antigen using
another chemical called CD4; this
initiates both the humoral and cellmediated responses
A Helper T cell tells the shape of the
antigen to the B cells so they can
make more antibodies, tells it to the
macrophages which will then eat the
invaders, and they activate the killer T
cells so they can kill the infected cells
Helper T cells basically initiate the
entire immune response
Acquired immunodeficiencies range
from temporary states to chronic
diseases
These are the cells that are being
infected by HIV
AIDS
•
People with AIDS are
highly susceptible to
opportunistic infections
and cancers that take
advantage of an immune
system in collapse
•
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You don’t die from aids, you
die from a secondary infection
Because AIDS arises from
loss of helper T cells, it
impairs both the humoral
and cell-mediated immune
responses
The loss of helper T cells
results from infection by
the human
immunodeficiency virus
(HIV)
Autoimmune Diseases
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In individuals with
autoimmune diseases,
the immune system
loses tolerance for self
and turns against
certain molecules of
the body
Rheumatoid arthritis is
an autoimmune
disease leading to
damage and
inflammation of joints
Multiple Sclerosis
Secondary Exposure

If you are exposed
to a virus that you
have previously
experienced, you
would already have
antibodies, memory
B and Memory T
cells that can be
quickly produced
and fight off the cold
before you feel its
effects.
Plant and Animal defense
mechanisms
Plant can use nonspecific
defense (have no immune
system response) – it kills
anything that invades or
moves inside the organism
 Hypersensitive response (a
plant can sense proteins
given off by bacteria by using
its “R” gene) – reminder from
ch. 39, plant responses
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Let’s off an oxidative burst, that
kills the cells, even if it’s not
infected
It also gives off a protein that
changes the cell walls of all the
adjacent cells
Doesn’t have memory, so it will go
through the same process if it’s
infected again