Download The Immune System File

The Immune System
The Immune System (p.382-386)
• a collection of cells and tissues that defend the
body against *pathogens that gain entry. The
major parts include:
– white blood cells (lymphocytes ie.B-cells &T-cells,
macrophages)
– lymphatic system (lymph, lymph vessels, nodes)
– blood (circulatory system)
– spleen
– thymus gland
– bone marrow
pathogens -> any disease-causing agent eg.
bacteria, viruses, fungi, parasites.
• We keep pathogens from taking over our
bodies and causing disease through:
• I. Non-specific defences
• II. Specific defences
I. Non-specific defences
• guard against wide variety of pathogens,
regardless of their cause (general).
• effectiveness does not depend on prior
exposure
• Two Types:
– A. First line
– B. Second line
A. First line of defence:
(physical and chemical barriers)
1. Skin
• protective layer - prevents entry on most of the body
• Inhospitable (dry and contains indigestible keratin)
• constantly shedding old cells- gets rid of pathogens
that may be growing
• oil (containing bactericide) and sweat glands –
produces acidic environment: hard for microorganisms
to grow
• burn victims - open to infections - why?
1st Line cont’d
2. Mucus, hairs and cilia
• Mucus - found in digestive and
respiratory tracts
• mucus is wet and sticky, traps dirt and
pathogens in the trachea and digestive
tract
• Cilia - hair-like structures that grow in
the lining of the respiratory tract; they
wave mucus upward to the throat where
it is coughed up, sneezed out or
swallowed to the stomach
1st Line cont’d
3. Acids and digestive enzymes
(chemical)
• acids in the stomach
(hydrochloric acid ) kills most
bacteria
4. Secretions of the body
• eg. tears, saliva, nasal secretions
• contain lysozymes, which break
down the cell walls of bacteria
(killing them and preventing
reproduction)
1st Line cont’d
5. Urine
• flushes out unwanted
pathogens by filtering
waste from the blood in
the kidneys
B. Second line of defence:
(still a non-specific defence)
1. The inflammatory response
• damaged cells release chemicals (eg. histamine)
Histamine causes:
• blood vessel dilation (increases blood flow
(redness) and temperature). May be enough to
destroy/neutralize some pathogens
• Capillaries to be more porous, allowing tissue
fluid to gather in the area (swelling)
• soreness
2nd line cont’d…
2. Fever
• macrophages, after engulfing (eating)
pathogens, secrete chemicals that produce a
fever
• the body raises its thermostat; the higher
temperature kills pathogens (ok to a certain
point - why?
2nd line cont’d…
3. Use of Phagocytosis
• cells that kill bacteria by ingesting them
• (i) macrophages -> phagocytic cells found in liver,
spleen, brain and lungs. They circulate in the
bloodstream and tissue fluid, looking for
pathogens to engulf
• (ii) neutrophils and monocytes -> white blood
cells that attack bacteria
– dead macrophages and bacteria are visible as pus at
the site of infection
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter22/animation__the_immune_response.html
II. Specific defence (third line of defence)
• i.e., the immune response
• The body produces *immunity by the production of
**antibodies to destroy the pathogen.
• The first encounter with the pathogen results in the
creation of the immunity and is called the primary immune
response.
• Should the pathogen enter the body a second time, the
body reacts with the secondary immune response, which is
faster acting and the person displays fewer symptoms.
• * immunity -> the ability of the body to resist disease, after
being exposed to it in the past.
• **antibodies -> a Y-shaped protein formed in response to a
virus or other foreign substance in the blood or tissues.
(p.384 Fig.11-27)
Immunity may be active or passive.
Active Immunity
• long lasting (years)
• body is exposed to pathogen, goes through the specific
immune response and develops an immunity against the
pathogen
• eg. accidental exposure (chicken pox), vaccines
• vaccine - injecting dead/weakened pathogens into the system,
causing an immune response
• If the person is later exposed to the ‘actual’ (stronger)
pathogen they will either not get ill or not as ill, as they
would’ve without the vaccine.
• eg. whooping cough, mumps, polio, measles and chicken pox
https://www.youtube.com/watch?v=B_hCLWtEHL8 – How anti-vaxxers sound to
normal people
https://www.youtube.com/watch?v=nDjz5qHIzsc - If Anti-Vaccine Parents
Rode The Magic School Bus
Passive Immunity
• is temporary (usually lasting only a few months)
• immunities passed on from one person to
another
• eg. pregnant mother passes on immunities to
unborn child through the placenta and to a
newborn through breastfeeding.
• Breastfeeding prolongs the passive immunity
(makes it longer lasting)
May 26
Review:
• Cell-mediated immune response
http://www.youtube.com/watch?v=1tBOmG0QMbA&safety_mode=true&persist_
safety_mode=1&safe=active
• Antibody mediated immune response
http://www.youtube.com/watch?v=hQmaPwP0KRI&safety_mode=true&persist_safety
_mode=1&safe=active
AIDS - p. 124 & 496
• Acquired Immune Deficiency Syndrome (disease) – caused by the
Human Immunodeficiency Virus
• HIV is a retrovirus; i.e., it has RNA as its nucleic acid (genetic
material) instead of DNA
How does HIV cause AIDS?
• HIV attacks helper T-cells.
• They move into the nuclei and may remain dormant (inactive) for
up to 10 years. Thus you may have the virus but not the disease.
• Once the virus becomes active, it uses the DNA machinery in the
host’s nucleus to replicate itself.
• The many viruses then leave the helper T-cells (now destroyed), to
infect other helper T-cells and macrophages.
• Results in a weakened immune system, making the
body vulnerable to many diseases.
• AIDS victims often die of pneumonia or rare cancers.
• HIV is difficult to make a vaccine for since:
– it mutates quickly, so that a vaccine is no longer
effective
– it can stick helper T-cells together and so move
from cell to cell without having to deal with
antibodies in the blood or tissue fluid
– there are millions of strains (versions) of the virus)
AIDS is spread through:
• 1. Direct contact with bodily fluids
– semen (through sexual contact) & vaginal fluid
– blood (cuts, transfusions)
• 2. Sharing of contaminated hypodermic needles
• 3. From mother to child (through the placenta) or during birth
AIDS can be prevented by:
• Avoiding sexual contact with infected individuals (using latex
condoms and spermicides)
• Avoid blood transfusions with infected individuals (since 1985 blood
is screened through testing)
There is no cure!
• There are treatments – a wide variety of drugs often administered
together (cocktail)
• Do questions: p.386 #1,2,3,5,6,7; P.388-89 #24,25,31,36,39,41
Immune System Malfunctions
1. Autoimmune Diseases/Disorders (p.386)
• when T-cells or antibodies mistakenly attack the body’s
own tissues as if they had foreign antigens; cause is
unknown
• Often inherited; some start after recovery from an
infection or injury
• can be very serious and debilitating
• eg: (a) multiple sclerosis -> body attacks the myelin
covering of nerves
(b) lupus -> disease of 1000 faces (varied
symptoms)
•
•
•
•
(c) rheumatoid arthritis ->
inflammation of the lining of the joints
continues into bone, cartilage, tendons and ligaments
causes pain, stiffness, fever, swelling, fatigue, and loss
of appetite.
• Treatment may include (1) non-steroidal antiinflammatory drugs, (NSAID’s) to reduce pain and
inflammation, (2) aspirin, (3) steroids, or (4)
corticosteroids.
• commonly affected joints are wrists, knuckles, elbows,
shoulders, feet, ankles, hips, knees.
2. Allergies
• An allergy is an exaggerated response by the immune system
to a harmless material such as pollen, mould, or cat (animal)
dander.
Two types of allergic reactions are:
• immediate (acute)
–
–
–
–
*most common
occurs within seconds of exposure to allergen
usually disappears within 30 min.
specialized antibodies can cause watery eyes and runny nose.
They can trigger certain cells to release histamines causing
swelling and redness.
– some forms of asthma are acute reactions to inhaled allergens
which then trigger a massive release of histamines, setting off
spasms of the bronchioles
• Delayed
– less common
– several exposures results in an allergic reaction
buildup over time
– Food allergies can trigger vomiting, cramps and
diarrhea
– Most allergies can be treated with antihistamines.
– more severe - Epi pen
Extra Info if you want/need review
The Lymphatic System - p. 322-323; Fig. 9.24 &
9.25
• The lymphatic system consists of:
– (a) lymph vessels - similar to veins in that they have
valves that help direct the lymph forward (no pump!)
– (b) lymph - contains tissue fluid (water, salts, gases,
chemicals, hormones) and white blood cells but no
red blood cells
– (c) lymph nodes - swellings found at various places in
the body where white blood cells gather pathogens to
destroy them
Functions
• 1. Combats disease by collecting harmful
microorganisms (pathogens), filtering them from the
blood and bringing them to lymph nodes (Immune)
• 2. Siphons off excess fluid from around body cells and
dumping in back into the thoracic duct located just
superior (above) to the heart (circulatory)
• 3. Absorbs fatty acids and glycerol into lacteals in the
villi of the small intestine (digestive) and dumps it back
into the circulatory system .
The primary immune response
Four phases:
1. Invader identification
• macrophages engulf pathogens and display pathogen
*antigens on their cell membranes
• helper **T-cells bind to the antigens, triggering the release
of a chemical signal for other helper T-cells to clone
* antigens -> any substance that causes an immune
response. Viruses and microorganisms have substances on
their outer surface that are antigens; eg. of antigens:
proteins, carbohydrates, nucleic acids
** T-cells mature in the thymus gland (found in your chest)
The primary immune response
Four phases:
2. Cloning phase
• helper T-cells clone (divide to make many) and
stimulates killer T-cells (also called cytotoxic T
cells) and *B-cells to clone also.
* B-cells mature in the bone marrow
The primary immune response
Four phases:
3. Attack phase
• B-cells produce antibodies
• They bind to the antigen on the pathogen,
causing them to clump together in bunches
• Now they’re ready for the macrophages to engulf
them
• Antibodies (Y-shaped) may be attached to the Bcell membranes or allowed to float in the blood
plasma, lymph or tissue fluid, ready to tag
pathogens.
The primary immune response
Four phases:
• T-cells may bind to the B-cell antibody-antigen
complex, activating the B-cell.
• This causes the B-cell to enlarge and divide,
producing plasma cells and memory cells.
• Plasma cells produce large amounts of the
same kind of antibodies carried by the B-cells.
• When the danger has passed, plasma cells
undergo apoptosis (which means
programmed cell death).
The primary immune response
Four phases:
• cytotoxic T-cells puncture diseased cell
membranes causing the pathogens to flow out
while macrophages lie ready to engulf them.
• Cytotoxic T-cells attack cells that are being
infected by bacteria or viruses and cancer
cells.
• The attack continues until the disease is
brought under control.
The primary immune response
Four phases:
4. Slowdown / Memory phase
(a) Slowdown
• suppressor T-cells slow down the cloning until the numbers of helper
• T-cells, B-cells, and cytotoxic T-cells are back to normal
(b) Memory
• special memory B-cells and cytotoxic T-cells remember that pathogen
should it come again.
• The body has developed an immunity against that pathogen.
• If exposed to it a second time, the memory cells will quickly produce the
antibodies to destroy them.
• This is the secondary immune response.
• Note: Refer to handouts on the primary and secondary immune responses
and Immune Response
• Immune System, White Blood Cells, T-Cells, Cancer
Cells 2:50
http://www.youtube.com/watch?v=an6NrTgCDFQ&safety
_mode=true&persist_safety_mode=1&safe=active
• Immune System - Natural Killer Cell - The Formulation
3:01 http://www.youtube.com/watch?v=z3a3AKhIb0&safety_mode=true&persist_safety_mode=1&safe=
active