Download Immune System

The Body's Defenses
The Immune System
Main Point #1

The body is first protected by a
barrier
The Outermost Barriers
Slightly acidic,
dry skin
 Prevents
living things
from growing
on us

The Integumentary System
Skin Secretions



Make skin acidic
Saliva, tears and
mucous all wash
away most
harmful bacteria
Secretions
contain
antibacterial
proteins such as
lysozyme
Mucus



Traps microbes and
particles
Swallowed and acid
from the stomach
kills bacteria
We also expel
mucus through
sneezing and runny
noses (rhinorreah)
Main Point #2

We have a non-specific immune
system that attacks any invading
pathogen
Non-Specific Responses

The body
has white
blood cells
that attack
any foreign
invaders
Neutrophils




WBCs attracted
to damaged cells
Engulf and
destroy microbes
via phagocytosis
60-70% of all
WBCs
Short life-span
Monocytes




More effective
phagocytes
Form
macrophages
Attach to bacterial
surfaces and digest
bacteria with
lysosomes
Only about 5% of
WBCs
Eosinophils


Fight off larger invaders
Shoot enzymes at large parasites
such as blood flukes
Natural Killer

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Destroy virusinfected body
cells
Burst the
membrane of a
cell, destroying
it
Protects against
viral takeovers
and tumors
Inflammatory Response


Cuts or bacterial
infections cause
the release of
histamines by
basophil and
mast cells
This causes
blood to flow to
capillaries to cuts
and infections
Inflammation con.


Increased blood flow brings clotting
factors as well as WBCs to attack the
invader
Fluid and WBCs leak out of capillaries,
which is why injured areas swell
Main Point #3

The third line of defense is
specific reactions to disruption
of homeostasis
Lymphocytes



WBCs that
circulate in
blood and lymph
2 types
 T Cells
 B Cells
Recognize
foreign invaders
B Cells


Foreign
molecules called
antigens are
recognized by B
Cell's receptors
B cells release
antiBodies
which identify
and attack
specific foreign
invaders
T Cells


Identify and
attack invaders
It is T cells that
are attacked by
the AIDS virus
Quick Note
• Antigen = foreign molecule
• Pathogen = foreign organism
• Often used interchangeably
• WBCs may recognize an
antigen that is a part of a
pathogen
Once An Antigen Binds...

Lymphocytes
divide into 2 sets
of cells


Effector
cells which
fight the
infection
Memory
cells which
are longlived
Quick Review



We have millions
of lymphocytes
Binding of antigen
triggers cell
division
Creates a specific
response
Primary vs. Secondary
Immune Response



It takes about 10-17 days to generate the
maximum response to a foreign microbe
and clear the antigens from the body
During the wait time is when people feel ill
If exposed to the same antigen, it takes
only 2-7 days to clear the body, which is
called the Secondary Immune Response

More antibodies that are more specific
are made due to memory cells

This is called immunological memory
Self-Tolerance



When lymphocytes
are being made
they are tested with
molecules from the
body
Any T or B cell that
reacts to the body is
destroyed
This, however, goes
wrong in diseases
like multiple
sclerosis
Main Point #4

Specific immune responses
consist of antibodies and T
cells fighting off foreign
antigens
Immune Responses

The humoral
response defends
against
extracellular
antigens (in the
blood)

Formation of
antibodies in
blood

The cell-mediated
response defends
against pathogens
inside of cells

Destruction of
infected or
cancerous
cells
Helper T Cells



Help stimulate
both responses
Important in
recognizing
antigens a
second time
It is these
specific T cells
that HIV and
AIDS affect
Cell-Mediated Response


T cells divide into
memory cells and
active cytotoxic T
cells
Active Cytotoxic T
cells lyse and burst
infected and
cancerous cells
Humoral Immunity Overview



B cells give rise to
plasma cells and
memory B cells
Plasma cells
secrete antibodies
Antibodies bind
antigens and help
the eliminate them
Main Point #5

Antibodies help fight viruses
and bacteria outside of the
cells in a number of different
ways
Antibodies
Proteins that
can bind
multiple
antigens
 Helps disposal
of pathogens
in a number of
ways

Neutralization


Antibody binds
and blocks
activity of
antigen
i.e. an antibody
can bind to the
part of a virus
that inserts the
virus into cells
Opsonization

Antibodies bind
and make it
easier for
macrophages
to digest
pathogen
Agglutination



Antibodies can clump bacteria or
viruses together
Antibodies have multiple attachment
sites
Makes it easier for phagocytes to digest
Review
1. Barriers
•
Skin/mucus/lysozyme
2. Inflammatory Response
•
Basophil/Mast cells release histamine
•
Swelling, non-specific WBCs
•
Neutrophils, Monocytes (macrophages),
eosinophils, natural killer cells
3. Immune Response
•
Lymphocytes attack specific antigens
•
Humoral (B cells, antibodies) and Cellmediated (T cells)
Major Histocompatibility
Complex (MHC)
• Molecules on cell surface that help
the body distinguish self from nonself
• WBCs recognize non-self antigens
and attack
• More diverse MHC molecules
means better immune defense
MHC Diversity
• Each person
has a very
unique set of
glycoproteins
on all of their
cells
• Changes
when there
are cancers
MHC Diversity and Mate
Selection?
• Many studies have shown
preference for mates with
different MHC markers
• Part of scents?
The Immune System Makes
Tissue Transplant Difficult
• The body
recognizes
foreign tissues
and attacks it
• Easier to use
tissue from
one's own body
Tissue Transplants
•
The MHC recognizes
foreign tissues
•
Donors and recipients
must be closely
matched
•
Twins and siblings are
usually the closest
matches
Blood Transfusions
•
Blood types can be considered antigens
•
Type A produces A antigens, B produces B
antigens, O produces no antigens
•
People with B or O blood types produces A
antibodies
•
People with O blood produce both antibodies
(can't receive A or B blood)
Blood Transfusions Gone
Wrong
• You cannot receive blood for which you
have antibodies!
• If you’re type O, you produce A and B
antibodies – you can only receive type O
blood
• If you’re AB – you produce no antibodies –
you can accept any blood
• (this oversimplifies things a bit, there is
also the Rh factor and other blood
antigens)
Immune System
Commercials/Ads


Solo, duo or trio. No quartet
Either in a written ad or a video commercial,
advertise:

Basophil/mast cells (histamine)

Macrophages/monocytes

T cells

B cells

Antibodies

Optional additions: neutrophils, MHC, helper T,
eosinophils, natural killer