Transcript Blood and Immunity - Salisbury Composite High School

Blood and Immunity
What is Blood?
• Blood is a fluid tissue. It is important for the
protection and survival of all our bodies cells. The
average person has about 5 L of blood. Of this:
•
55% is fluid called plasma
- mainly water, minor dissolved O2, CO2,
nutrients, waste, salts, hormones and vitamins
•
<1% is white blood cells and platelets
•
45% is cells suspended in fluid
RBC – erythrocytes-have no nucleus
WBC – leukocytes-have a nucleus
Platelets – thrombocytes-have no nucleus
• The two components
of blood can be
separated using a
centrifuge. This is an
apparatus that spins
blood in test tubes
forcing the solid
particles to the bottom
and the plasma to the
top. This mechanical
separation allows us to
separate and use
various blood products.
Formation of Blood Cells
Blood helps us to maintain homeostasis. It is
involved with:
1. transports O2 and CO2
2. transports salts and minerals
3. clotting
4. maintaining pH
5. infection fighting
6. maintaining temperature
7. maintaining water balance
• We will focus on three main functions of blood; transport,
clotting, and infection fighting in more detail…
Transport
• Blood carries O2 from the lungs to the tissues, and
CO2 from the tissues to the lungs. It also carries
nutrients absorbed by the digestive tract to the
tissues, and carries wastes from the tissues to the
kidneys for excretion. Transport is facilitated by a
number of blood components:
Blood proteins
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albumin – transports bilirubin and regulates water
balance
fibrinogen – involved in clotting
globulins – fight infection, transport cholesterols
These proteins help to maintain viscosity (thickness)
of blood so it can flow. They also help to create an
osmotic pressure and keep blood volume constant.
Red blood cells (erythrocytes)
• Contain special protein units called hemoglobin,
which is made up of 4 polypeptide chains (globin)
and iron (heme). The function of hemoglobin is to
carry oxygen. Also these do not have a nucleus
• Carbon monoxide has a higher affinity for
hemoglobin than oxygen does, so it can easily bind,
causing carbon monoxide poisoning. There are
about 200 million molecules of hemoglobin in each
red blood cell, and about 500 million red blood
cells in 1 mL of blood! Red blood cells are
manufactured in the bone marrow of the skull,
ribs, vertebrae and long bones. These cells only
live for about 120 days, after which, they are
broken down by the liver and the spleen. The
iron from the hemoglobin is recycled, and the
heme group is used as a bile pigment.
The role of hemoglobin
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At high altitudes, oxygen levels are low, so the body
increases the number of red blood cells. Athletes often
train at high altitudes to increase their number of RBC’s,
so they can exchange more oxygen. A number of
disorders of RBC’s can also occur.
Anemia – is a deficiency in the number of RBC’s,
resulting from an iron deficiency. Symptoms include
tiredness, feeling run down, and hair loss.
Sickle Cell Anemia – is a genetic disorder where the
RBC’s are no longer donut shaped, but sickle shaped.
Because of this mutation, the RBC’s do not efficiently
transport oxygen, and they don’t flow as easily through
the blood vessels.
Pernicious Anemia – vitamin B12 is not absorbed from
the intestines, (B12 is necessary for RBC formation).
• Carbon dioxide is produced in cells as a by-product of
cellular respiration. It is also transported in the blood, to
the lungs where it will be removed. Carbon dioxide can join
to hemoglobin to produce a carbaminohemoglobin (similar
to the transport of oxygen). Most carbon dioxide, with the
help of water in the blood, is transported as HCO3-:
Carbon dioxide is exhaled by the lungs.
H+ is carried in the blood plasma, and maintains
the blood pH.
HCO3- acts as a buffer in the blood.
Blood pH is about 7.4
Blood Clotting
• When injury occurs, blood must clot / coagulate to prevent
further blood loss. The clotting process requires three
substances; platelets, prothrombin, and fibrinogen.
• Platelets are specialized cell fragments, from
megakaryocytes in the red bone marrow, that do not contain
a nucleus. They have jagged edges that help to initiate the
blood clotting process.
• Prothrombin is a protein involved with blood clotting that
is made with the help of vitamin K, by the liver. This
protein is converted to the enzyme thrombin, with the aid of
calcium ions.
• Fibrinogen is a long chain protein, also made by the liver.
With the help of the enzyme thrombin, fibrinogen is broken
down into smaller fragments that form threads called fibrin.
Blood Clotting
• Damaged platelets and tissue
cells release thromboplastin ( a
prothrombin activator)

• Thromboplastin releases
calcium ions to cause
prothrombin to becomethe
enzyme thrombin thrombin.

• The enzyme thrombin cause
fibrinogen to become fibrin,
which is the key component
of the clotting process.
• A clot consists of platelets and blood cells all tangled
together in fibrin threads. The clotting process is
enzymatic, so it can be sped up with increased
temperatures. Once blood vessels repair, plasmin
destroys the fibrin threads, and restores circulation.
The remaining yellow liquid (blood plasma without
fibrin) is called serum.
• Hemostasis
Problems with blood clotting:
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•
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Thrombus – is a blood clot that forms in a blood
vessel, cutting off the blood flow, and oxygen supply.
Embolus – is a blood clot that dislodges and is
carried by the circulatory system to vital organs. If
the clot stops, blocking blood vessels in the brain, this
is called a cerebral embolism, or more commonly
known as a stroke. If a clot blocks blood flow in the
heart, this is called a coronary embolism, or more
commonly known as a heart attack.
Hemophilia – is an inherited clotting disorder,
where a person lacks clotting factors. The blood does
not clot appropriately without this clotting factor to
initiate the process.
Blood Groups
• Glycoproteins are large complexes of carbohydrates and
proteins found on the membranes of red blood cells.
These complexes act as markers, and are recognized as
being friend or foe (foreign antigens) by cells that don’t
have them. A person receiving blood or tissue
containing foreign markers (antigen) will develop
antibodies to that blood or tissue and reject it. This will
cause the blood to agglutinate (clump), clogging
capillaries and prevent oxygen and nutrient exchange.
Other Blood Group Factors
• Rhesus (Rh) factor is another level of blood-typing.
About 85% of Canadians are Rh+, and have the Rh
antigen. About 15% are Rh- and don’t have the antigen.
Antibodies to the rhesus factor would only be produced
after a blood transfusion. In adults, the immune
response is mild, but in children it can be fatal. Major
problems arise with an Rh+ baby in an Rh- mother. At
the birth of a first Rh+ child, the mother’s blood mixes
with the baby’s, and the mother will make antibodies to
the Rh+ type. If a second child Rh+ child is conceived,
the mother’s antibodies can cross the placental barrier
causing the child’s blood to clump, and the baby to die.
This condition is called erythroblastosis fetalis (blue
baby). This can be treated either by giving mom a drug
that inhibits formation of antibodies against the Rh+
antigens, or by transfusing the baby with Rh- blood.
Blood type is tested by exposing blood samples to Anti A, Anti
B, and Anti Rh antibodies. If agglutination (clumping)
occurs, the person has that antigen on their red blood cells.
Blood Typing
Fighting Infection
• The body has two lines
of defense in fighting
infections. The first line
of defense involves:
1. skin
2. mucous and cilia in
respiratory tract
3. stomach acids to
destroy invaders
4. lysozyme in tears
(all are physical barriers)
If the first defense fails, a second line of
defense is used. This involves:
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Leukocytes (white blood cells) engulfing particles
Lymphocytes producing antibodies
– T cells – stored in the thymus gland, identify
invaders and call B cells into action.
– B cells – made in the bone marrow, make
antibodies to the antigens.
• Globulins – are complementary proteins that
form a coating around the invader, sealing it in
attach to the invader and dissolve the cell membrane
attach to the invader and attract white blood cells.
(antibodies=immunoglobulin)
Leukocytes (white blood cells)
• Are much less numerous than red blood cells (700:1),
and have a nucleus, making them easily distinguishable
from red blood cells. Some leukocytes destroy microbes
by diapedesis. They squeeze out of capillaries and
move toward the microbe like an amoeba., engulf the
microbe and release enzymes that digest the microbe
and the leukocyte. The remaining substance is called
puss. Other leukocytes produce antibodies that
interfere with the normal functioning of toxins or
microbes.
• www.ac-creteil.fr/biotechnologies : La diapédèse
There are 2 types of leukocytes:
•
1. Granulocytes – formed in the bone marrow, have
granules in the cytoplasm
– Neutrophils – 60-70% - phagocytes
– Eosinophils – 2-4% - engulf antigen-antibody
complexes
– Basophils – release histamines, that cause
capillaries to dilate
• 2. Agranulocytes – formed in the lymph tissue,
have no granules in the cytoplasm
– Lymphocytes – 25-30% make antibodies in lymph
and blood
– Monocytes – phagocytes, engulf foreign cells
Antigen – Antibody Reactions
• Antigen – The ID card that identifies a
toxin, foreign material, bacteria, virus or
parasite.
• Antibodies – Y shaped proteins that
combine with an antigen to make it more
recognizable to macrophages (big cells that
eat stuff), and cause agglutination (clumping
of cells).
• Immunity – is the exposure of a cell to an
antigen, either naturally or injected in a
vaccine. This causes the immune response,
and antibodies to develop.
Immune Response
• When a macrophage’s cell membrane is pressed into an antigen,
Helper T-cells read the antigen’s shape, and release a chemical
messenger called lymphokine. This substance causes B-cells to
divide and produce antibodies. Killer T-cells are also activated to
puncture the cell membrane of the invader, thus killing the invading
cells. They also destroy mutated cells and potential cancerous cells.
Once the infection is controlled, Suppressor T-cells signal the
immune system to slow down. Most B and T cells will die off in a
few days, but, special cells called Memory T-cells hold an imprint of
the antigen, allowing your body to respond more quickly if a reoccurrence should occur. Mutated T and B cells (renegade cells) can
turn on the organism, and start attacking its own cells. This is called
an auto-immune disease.
• Tutorial 18.4 Humoral Immune Response
• Usually such events are held in check by
suppressor T-cells, but the process can fail:
– rheumatic fever causes attack and scarring of
the heart tissue
– rheumatoid arthritis is an attack against the
bones and connective tissue causing
degeneration
– some drugs or serious infections can weaken
suppressor cells, increasing vulnerability
– Specific Immunity Animation
Immune Response
Immune Disorders
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Mononucleosis – excess number of lymphocytes
caused by the Epstein-Barr virus
Leukemia – a form of cancer characterized by
excessive uncontrolled production of high levels of
poorly developed white blood cells
AIDS – is an infection caused by the HIV virus, and
is characterized by an abnormally low number of
leukocytes
Kuby, Immunology 4e
Allergies – occurs when the body recognizes
normally harmless substances as invaders, and the
immune response is set into action
Vaccinations
• Vaccinations involve introducing
dead or weakened microbes
(infectious particles) into the body.
The body responds by producing
antibodies. Virulent microbes
cause the disease before providing
immunity. Sometimes you get a
little sick after a flu shot.
Vaccinations are not new. They
have been used throughout history
• http://www.schoolscience.co.uk/c
ontent/4/biology/abpi/immune/i
mages/vaccination.swf
• The Chinese scraped small bits of dried skin from
smallpox victims and blew it into the nose of healthy
people.
• Edward Jenner, an English doctor is credited with the
first cowpox vaccine. He noticed that dairymaids had a
high incidence of cowpox, but a low incidence of
smallpox. He proposed that cowpox gave some
immunity to smallpox, so he injected the pus from a
maid infected with cowpox into a young boy who later
developed cowpox. Later, Jenner injected the boy with
smallpox, and the boy was unaffected. He was
immune!
• Louis Pasteur found ways to weaken the rabies virus.
He injected this weakened strain and found that it
caused the production of antibodies that gave immunity
to a full blown rabies attack.
• Jonas Salk introduced a polio vaccine in 1955. He
killed the virus with formaldehyde, and injected it into
test animals.
• Kuby, Immunology 4e
Monoclonal Antibodies
• Monoclonal antibodies are antibodies of one specific
type produced by plasma cells. They are produced by
removing a B lymphocyte from an animal and exposing
it to one kind of antigen. These activated plasma cells
are then fused with a myeloma (cancerous) cell to
produce many immortal hybridoma (hybrid cells).
These cells can be used to identify specific infections,
and to diagnose pregnancy. When exposed to the
antigen for which they are tagged, they cause
agglutination (clumping) of cells. Monoclonal
antibodies are also able to distinguish between normal
cells and cancerous cells, so they can be used to carry
radioactive materials or drugs to tumors.
Drugs
• Many types of drugs and antibiotics are used to
help fight infection.
• In 1945 mercury was used to treat syphilis
• Later, Salvarsan was used because it blocked
chemical reactions in the microbe with fewer side
effects
• In 1935 sulfanilamide was discovered as another
treatment for infections
• In 1929, Alexander Fleming discovered that mould
could overcome bacteria growing on an agar plate.
He realized that mould had antibacterial
properties.
• An antibiotic interferes with the production of bacterial
cell walls, causing the membranes to burst and the
bacteria to die.
• Unfortunately, micro-organisms have the ability to
mutate and become immune to antibiotics, so they can
become less effective if overused.
• Viruses do not respond to antibiotics! A viral infection
will clear up in 2 weeks with antibiotics, or 14 days
without!