Transcript Immune System New

Immune System
Mincer/Scully
Immune System
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Function: To protect and defend the body
against invasion by pathogens.
No major organ, there are a few that help out:
Spleen
 Thymus
 Bone Marrow
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Pathogen
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Pathogen: A biological agent that causes disease
in its host.
Virus
Bacteria
Fungus
Protist
Disease
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Disease-Any disruption of homeostasis
which causes specific symptoms, and can cause
death if untreated or the immune system is
unable to fight it off.
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E.g. infection by pathogen, genetic disorder
Germ Theory
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People used to think that evil spirits or demons
caused disease.
Pasteur’s investigation led to the theory that
many diseases are caused by biological agents,
like bacteria.
This is called the Germ Theory of Disease
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Infectious diseases are caused by biological agents
Infectious Agents-Virus
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Virus- strand of DNA or RNA wrapped in a
protein coating.
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Invade a cell (or inject their nucleic acid into a cell)
and then cause the cell to make more viruses rather
than the cell’s normal function.
Bacteria
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Bacteria- Prokaryotic cells
Mostly harmless, but some can live and thrive
(and cause disease) inside the body
Sometimes can be cured by antibiotics
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Superbugs have arisen due to overuse of antibiotics
(accidental artificial selection)
Superbugs
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So-called superbugs are bacteria that have
evolved a resistance to most antibiotics.
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MRSA (Methicillin-resistant Staphylococcus aureus)
is an example. S. aureus is typically found on your
skin and can cause pimples. But, if you become
infected with MRSA, then it may be life-threatening.
How Do Superbugs Develop
Resistance?
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Its simple, really:
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In any population, some bacteria may have the genes
that make them immune to the effects of the antibiotics.
If antibiotics are used, the bacteria that aren’t immune
die, leaving behind ONLY the ones that have those
genes. Therefore, all their offspring will have those
genes, and therefore be immune.
Superbugs-Resistance is Futile
Only a few bacteria (red) have
the gene that give resistance to
the antibiotic. The others (blue)
don’t.
The bacteria that survive
now all have the genetic
resistance.
Those bacteria then
reproduce, and all of their
offspring have the
resistance too.
Fungi
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Fungi-very few members of the Fungi kingdom
can parasitize humans
The ones that can tend to attack the skin, but a
few can invade inside the body.
Protists
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Protists are eukaryotic and microscopic
organisms that cause disease
Examples:
Malaria
 African Sleeping Sickness
 Giardia
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How Do Diseases Spread?
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Physical contact
Skin to skin contact
 Exchange of bodily fluids
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Indirect contact
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E.g. sneezing and coughing
Vectors
Vector
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A vector is the method by which a pathogen is
transmitted to humans.
It might NOT be what actually causes the illness
 E.g. A mosquito bites your arm, and the protist
Plasmodium is transmitted into your bloodstream or a
tick bites you and a Borrielia bacteria is transferred
and you have Lyme disease
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Prevention of Disease
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Good hygiene
WASH YOUR HANDS
COVER YOUR MOUTH AND NOSE
Treatments
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Antibiotics-Drugs which kill or weaken bacteria
Don’t work on viral infections, like colds
 E.g. Penicillin, streptomycin, sulfonamides
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Treatments
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Rest
Fluids (like orange juice)
Balanced diet
Check with a doctor
Immune System
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Function: To protect and defend the body
against pathogens
Made of a few smaller organs and white blood
cells
Lymph
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Lymph is extracellular fluid that white blood
cells can travel through.
Spleen is an organ that filters bacteria and
broken cells from the lymph
Lymph nodes are also filters
How does the Immune System
Work?
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There are two ways in which the immune system
operates:
Nonspecific defenses- Tries to keep everything
out
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Skin, mucus, cilia, tears, stomach acid, etc.
Specific Defenses- Fights off infection once the
pathogen gets inside the body.
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White Blood Cells (WBC’s)
Immune Response
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If the pathogen gets inside anyway, there are things
your body usually does to try to slow the invader
down.
Fever- raising body temperature to help denature the
pathogen’s proteins
Expand blood vessels- WBC’s can get to the infection
site more quickly
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This is called inflammation, and can be painful
Allergies
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An allergy is a condition where the body
misrecognizes something that is harmless as a
pathogen
Histamines are the chemicals released to cause the
inflammatory response
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Example: Pollen can cause a fever, runny nose, and
sneezing
Some allergies can trigger a severe reaction, called
anaphylactic shock
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This can cause choking due to a constricted airway
Allergens
White Blood Cells
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White blood cells are the soldiers of the body
They seek out and destroy pathogens
Have several different names: WBC’s,
Lymphocytes, Leukocytes, Phagocytes
White Blood Cell Types
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T Cells
These are the recon cells.
 They travel through the body in search of pathogens
 When they find a pathogen, they engulf it and
destroy it, then they do something weird
 They display parts of the pathogen on their
membranes
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Antigens
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The part of the pathogen that the T Cells display
is called the antigen
Antigens are proteins that all cells have on their
membranes
The shape of the antigen varies according to the
species of pathogen
Sometimes, the pathogen itself is referred to as
an antigen
Then…
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The T Cells show the antigen to the other type
of WBC:
B Cells- These cells search their memories. If
the B cells have seen this antigen before, they
get to work mass producing antibodies
If the B cells haven’t, they start to build
antibodies from scratch
Antibodies
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Antibody- a protein molecule which attaches to
the antigen on a pathogen and then either:
1. The antibody causes the pathogen to be unable to
enter any more body cells
 2. The antibody attracts a WBC to engulf the
pathogen
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Immunity
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Immunity is the condition your body has when it
already knows how to make the antibodies for a
specific disease.
This is why if you get sick with an illness and fight it
off (without drugs) you can’t get the same illness
again
When your T Cells show your B Cells a pathogen that
has been seen before; the B Cells immediately start
making the correct antibodies
Immunity
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Two types of immunity
Active: Your body knows how to make the
antibodies
 Passive: You receive antibodies from another
source, but your body doesn’t know how to make
them
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Mother’s milk
 Injection of antibodies
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Active Immunity
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There are two ways to get active immunity:
1. Get infected with the illness and fight it off—
your body learns how to make the antibodies
 2. Get a vaccination, which is a weakened or dead
form of the disease, and your body can still learn
how to make the antibodies, but you don’t get sick
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Vaccinations
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Vaccinations are only done for viral pathogens
Scientists create weakened versions of the virus
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They do this by incubating the viruses in chicken
eggs for several generations; this causes the virus to
become less infectious
Organ Transplants
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When a person receives someone else's organ,
the organ has foreign antigens on it.
The recipient’s white blood cells will recognize
the organ as foreign, and attack it.
So, the recipient has to take
immunosuppressant drugs
HIV
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Human Immunodeficiency Virus
This virus attacks human White Blood Cells
Easily mutates, so its hard to treat or destroy, or
vaccinate against
HIV-AIDS
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HIV is transmitted by bodily fluid contact
Sexual contact
 Blood-to-blood contact
 Using unclean needles
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HIV causes AIDS
AIDSAcquired Immune Deficiency Syndrome
AIDS
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Over 33.2 million people worldwide are infected
with HIV
The infection takes a long time (up to 10 years)
to develop to the point of causing AIDS
AIDS- The symptoms are very complex, but
usually there are weird infections, like fungal
infections, that rarely if ever occur when a person
has a healthy immune system