Download Ch. 11

Ch. 11
Part 2-Types of Cells and
Phagocytosis
•WBCs
• Contain
nucleus
• 3 types in 2
catergories
• Phagocytes
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Granulocytes
(phagocytes)
Monocytes
(phagocytes)
• Lymphocytes
•Phagocytes: made in bone marrow
Scavengers; remove dead cells and microorganisms
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*Neutrophils (granulocyte)
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form 60-70 % of WBCs; patrol tissues
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Engulf invaders until they themselves die
*Macrophages
• Stationary inside tissues (liver, spleen, lungs, kidney, lymph
nodes)
• Travel through blood as monocytes…once they settle in an
organ, they become a MACROPHAGE
• slower to respond to invaders than the granulocyte but they
are larger, live longer, and have far greater capacities
• Do not completely destroy pathogen…break it up and display
antigens to other WBCs
• INITATE immune response by displaying antigens of pathogen
Eosinophils kill parasites; antigen presenting cells
Dendritic cells like macrophages; stimulate development of
acquired immunity; antigen presentation
•KNOW:
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Sequence of Phagocytosis
Diagram sequence of phagocytosis
1. Attraction (chemotaxis)
2. Recognition and attachment
• Neutrophil has cell surface membrane
proteins called “receptors”
• Receptors recognize bacteria marked by
antibodies
• Neutrophil attaches to antibody-marked
pathogen
3. Endocytosis
4. Phagocytic vacuole containing bacteria is now
inside the cell
5. Lysosomes fuse with phagocytic vacuole
6. Bacteria within in phagocytic vacuole is killed
and destroyed
•Know the Stages of Phagocytosis
Attraction
1.
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Chemotaxis  phagocyte is attracted to
bacterium b/c of chemicals released by
bacterium OR by infected cells or other activated
WBC releasing histamine
Recognition and attachment
2.
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Directly to membrane
Indirectly via antibody receptor
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Endocytosis
3.
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Cell membrane of phagocyte surround attached
bacterium
Bacteria inside a phagocytic vacuole
4.
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Vacuole is now in cytoplasm of phagocyte
Lysosomes attracted to vacuole
Fusion of lysosome with phagocytic vacuole
5.
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6.
antibody attaches to bacterium, then then antibody
and bacterium attach to the antibody receptor in cell
membrane of phagocyte
Lysosomes release digestive enzymes that eat
away at bacterium
Killing of bacteria and digestion
•1. Granulocytes/Phagocytes (60% of
• Engulf or digest unwanted cells
WBC)
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(either damaged body or
pathogens) using enzymes
(granuoles in cell)
Larger than RBCs
Lobed nucleus (3-5 lobes)
enzymatic granules
Found in blood
Neutrophils: most prevalent;
ingest up to between around 5
and 20 bacteria in its lifetime;
travel in blood; squeeze through
capillaries to “PATROL” tissues
Eosinophils: involved in allergic
reactions; attack multicellular
parasites
Basophils: involved in allergic
reactions; release histamine,
which helps to trigger
inflammation
•2. Monocytes (phagocytes)
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Largest WBC large nucleus that takes up most of
cytoplasm; develop into:
Dendritic cells
• antigen-presenting cells; mark out cells that are
antigens (foreign bodies) that need to be destroyed
by lymphocytes
Macrophages
• phagocyte cells which are larger and live longer
than neutrophils; also act as antigen-presenting cells
• Stages of development:
1.
Born in born marrow as monocyte
2.
Travels through blood as monocyte
3.
Leaves bloods and settles in organs and
develops into MACROPHAGE
• Functions in organ, removing foreign matter
•Important Phagocytes
• Neutrophils
• Macrophages
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scavengers remove dead cells and invasive
microorganisms
Produced throughout life in bone marrow
• Attracted by chemical HISTAMINE and
other chemicals released by invading cells
• Histamine is released by infected cells
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•Chemicals Released by Injured Cells
Opsonisation
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refers to an immune process where particles such as bacteria are
targeted for destruction by an immune cell known as a phagocyte
process of opsonization is a means of identifying the invading particle
to the phagocyte
Opsonin
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Any substance (e.g. antibody) that binds to the surface of a particle
(e.g. antigen) to enhance the uptake of the particle by
a phagocyte (e.g. macrophage)
•3. Lymphocytes
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large nucleus that
takes up most of
cytoplasm
B cells
• Plasma cells
• Memory Cells
T Cells
• Helper T cells,
Cytotoxic T cells,
Killer T cells,
suppressor T
cells, memory T
cells
•B Cells
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B lymphocytes are able to release
antibodies
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Y shaped proteins that bind to infected
microbes or cells of the body that have
become infected
Antibodies can either neutralize the target
microbe or can mark it out for attack by T
lymphocytes and phagocytes
• Plasma Cells make antibodies
• Memory cells long lived, store
information about specific antigens
• Reproduce by mitosis Clones
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Helper T cells
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release a protein called cytokines which help to
further direct the response of other white blood cells
CYTOKINS stimulate cells to begin to divide by mitosis
Killer/Cytotoxic T cells
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also known as natural killer T cells
release molecules (cytotoxins) which kill viruses and
other antigens AND infected cells
Memory T cells
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present after the body has fought off an infection
help the body to deal more easily with any future
infection of the same type
• Made
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T Cells
from killer T cells and helper T cells
Regulatory T cells
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also known as suppressor T cells
help to regulate other T cells to prevent them
targeting the body's own cells; calls off attack
•Phagocytes Review
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Neutrophils
• 60%
of wbc
• Travel throughout the
body
• Leave the blood to
patrol tissues (by
squeezing through
capillaries
• During infection,
large # of these guys
are released
• Kamikazis-after killing
and digesting
pathogen, they
die…leave body as
pus
Originate in the bone marrow
Produced throughout lifetime
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Macrophages
• Larger
than neutrophils
• Found in organs: liver,
spleen, kidney, lymph
nodes
• Leave the bone marrow
as MONOCYTES, travel
to organs, and develop
in the organs into
Macrophages
• Long lived cells
• Initiate immune
response
• Do not destroy
pathogens completely
• Cut up pathogens and
display antigens for
other lymphocytes to
recognize
•Initial attack
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Cells under attack by a pathogen release a
chemical called HISTAMINES
These, with any chemicals released by
pathogens attract passing NEUTROPHILS to site
of infection
Neutrophils destroy pathogens
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Pathogens usually clustered b/c of antibodies
that are attached their antigens
Neutrophils have protein receptors on their
membranes that recognize the antibodies and
engulf the pathogen they are attached to
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Engulf pathogen…phagocytosis
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Becomes stored in a vacuole in WBC
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Inside the neutrophil, enzymes destroy the
pathogen
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But neutrophil also destroys itself…apoptosis
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Dead neutrophils leave your body as PUS
•Lymphocytes (specialized attackers)
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Smaller than phagocytes
Large Nucleus that fills up most of the cell
Origin: Produced in bone marrow BEFORE birth
Go to different organs to mature and develop
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Only MATURE lymphocytes can carry out immune response
Once mature, all B and T lymphocytes circulate the blood and
lymph …ensures they come in contact with each other and the
pathogens
On the surface of each lymphatic cell are receptors that
enable them to recognize foreign substances.
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very specialized receptors- each can match only one specific
Antigen
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•Lymphocytes
T cells
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Leave bone marrow and
collect in thymus, where
they MATURE
When mature, LEAVES
thymus and circulates
between blood and lymph
They become activated
when they come in contact
with:
• A macrophage
(antigen-presentation
cuts up pathogen and
displays antigens)
• An infected cell
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Its infected but it is
able to display the
antigens on its surface
to “call for help”
T cells come in two
different types, helper cells
and killer cells.
B cells
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Leave bone marrow and
collect and MATURE in
spleen and lymph nodes
When mature, circulates
between blood and lymph,
concentrating in LYMPH
NODES
JOB: search for antigens
matching its receptors,
connect and become
Partially ACTIVATED
FULL ACTIVATION require
proteins from helper T cells
Once FULLY ACTIVATED:
• the B cell starts to divide
to produce clones of
itself called plasma
cells and B memory
cells.
•B Cells (2 types)
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The plasma cell
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Job: Make antibodies that search for other similar
invaders
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Antibody finds invader, attaches to it and attracts
macrophages to come over and gobble up the invader
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Some Antibodies also neutralize toxins and
incapacitate viruses, preventing them from infecting
new cells.
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The Memory Cells
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Prolonged life span; can "remember" specific intruders (T
cells produce even better ones)
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The next time the same invader comes into body, B and T
memory cells help the immune system to activate much
faster
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Invaders are wiped out before the infected human feels
any symptoms
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Immunity against the invader has been achieved
•T Cells
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Two types
Helper T cells main regulators of the
immune defense
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JOB: activate B cells and killer T cells.
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must be activated by antigen
presentation
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Release CYTOKINES chemicals that
STIMULATE B cells to divide and
macrophages to attack more
vigorously
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Killer T cells
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specialized in attacking cells of the
body infected by viruses and by
bacteria (and sometimes cancer cells)
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Recognize antigens on invaders and
swiftly kill the EVIL invader (inject
cytotoxins into infected cell)
•T Cells
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Mature t cells have t receptors on
their membrane (similar to
antibodies)
T cells activated when they
encounter antigen in contact with
another host cell
Helper T Cells release cytokines,
stimulate B cell division and
strengthen the attack of
macrophages
Killer T Cells search body for
infected cells that are showing the
pathogens antigen
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release toxins into infected cells (like
hydrogen peroxide) to destroy them
Memory T cells  remain in body and
become active very quickly during
secondary response to antigens
•Killer T Cells
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Search body for cells that have become invaded
by pathogens (these cells are displaying antigens)
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Recognize antigens
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Attach to surface of infected cells
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Secrete toxic substance to kill infected body cell
and pathogens inside
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Ex. Hydrogen peroxide
Some Killer T cells secrete CYTOKINES that can:
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stimulate macrophages to carry out phagocytosis more
vigorously
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Stimulate killer T cells to divide by mitosis & to
differentiate by producing vacuoles full of toxins
•Memory T Cells
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2 Types
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Memory Killer T Cells
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Memory Helper T Cells
Both become quickly activated during secondary
response to antigens
•Number of WBCs
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Blood tests help doctors diagnose diseases and assess
success of treatments
Blood cells counted:
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Platelets
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Small cell fragments
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No nucleus
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Formed from breaking-up of cells in bone marrow
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Release fibrin  substance that stimulates blood clotting
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Red Blood Cells
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White Blood Cells
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Neutrophils  # increases during bacterial infection AND when tissues
become inflamed and die
Lymphocytes  # increases in viral infections and TB
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T-cells: make up a majority of lymphocytes in blood
•HIV and T-Cells
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HIV invades helper T cells and causes their destruction
Normal value:
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500 to 1500 cells mm-3
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HIV+ patients have significantly lower T-cell counts
Specific T-Cell numbers provide:
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Useful info on progress of disease
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Useful Info on success of treatments
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Important info about the deleterious affect of a disease on
the immune system (by monitoring declining T cell numbers)
Once the battle is done, the T-suppressor cell calls
off the troops so they can rest up for the next
battle!
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