Malfunctions of the
Immune System,
Pathogens & Immunity
Immune System Malfunction
• The immune system can cause two very
serious problems if it is not working properly:
– Inappropriate attacks against non-threatening
agents (Allergies).
– Immune-deficiency diseases (AIDS).
Allergies
• An allergy occurs when your immune system
mistakes harmless cells for harmful invaders.
Something harmless, like peanuts, mobilizes
an antibody strike. Increased tissue swelling
and mucous secretion, and sometimes
constricted air passages are all a part of this
response.
Allergic Response
• When you come into contact with the
“vicious” peanut, your cells perceive they are
in danger and release a chemical signal
called bradykinin which triggers the release
of another chemical signal called histamine.
• Histamine is produced by the basophils (a
type of white blood cell) and it changes the
cells of the capillaries – increases their size
and permeability. Proteins and white blood
cells can leave the capillary in search of the
“invader” and alter the osmotic pressure in
the blood vessel – this causes the swelling.
• Drugs such called antihistamines are used to
try and block their release and action.
Autoimmune Disease
• The immune system can go awry and
recognize the body’s own cells as invaders or
foreign entities. This could result in an attack
being launched by you against yourself.
• Renegade T cells and B cells are the problem –
they do the recognizing and attacking. They
can be held in check by suppressor T cells that
recognize these renegades and intercept them
before they can do any damage, but, if the
suppressor T cells do not stop them they break
the body down. This can be seen in such
diseases as rheumatoid arthritis, type 1
diabetes and lupus.
• The suppressor T cells can be weakened by
drugs or serious infections and this may open
you up to autoimmune diseases.
• Drugs exist that help lessen the intensity of
the renegade T and B cell attacks.
Pathogens & Disease
• A pathogen is any organism or entity that
causes disease within the body.
• Pathogens may include bacteria, viruses,
prions and a wide variety of parasites –
both protists and animals.
• Many diseases are believed to have
originated in domestic animals and,
through random mutation, become
communicable to humans. When a
disease is considered for its pathogenic
capabilities, both the virulence and
transmissibility of the disease are
examined.
Pathogens
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Bacteria
Viruses
A.I.D.S. Virus
Giardia lamblia – a
protist parasite.
• Plasmodium vivax –
protist – malaria.
• Trichinella – worm
– trichinosis.
How To Get Sick
Pathogens are transmitted through a variety of methods.
• Droplet Infection – A sneeze or cough can put out
thousands of water droplets that each contain many
microbes. These droplets can be inhaled or introduced
directly to the body through food water or skin contact.
• Waterborne – Some infections must enter the body through
water or they dry out and die quite quickly. The most
common cause of waterborne infections is unsanitary
disposal of waste near a water collecting area that is used
for drinking.
• Direct Contact – These infections are slower spreading and
can be avoided if the proper precaution is taken. Methods
of introduction include animal bites, unsanitary food
preparation, sexual contact and drug use with unclean
syringes.
• Vectors – A vector is a disease-carrying animal (usually an
insect) that picks up the microbes by hanging out near
waste that may be contaminated. They then transfer these
microbes when they come into contact with you. Lice,
ticks, fleas and mosquitoes are all excellent vectors.
Induced Immunity
• Induced immunity is an immune response
brought about by intervention from one’s own
body or form an outside source. There are two
forms of induced immunity – active immunity and
passive immunity – both are common.
• Active Immunity is gained when your own inner
workings produce antibodies against an invading
pathogen. Active immunity lasts a lifetime.
• Passive Immunity is protection (antibodies or an
inducer of antibody formation) that is introduced
into the body from an outside source such as a
vaccination. Passive immunity is often only
temporary in its effectiveness.
Vaccination
• A vaccine is an antigen-containing substance
that can be swallowed or injected to provide
continued immunity to a specific
disease/pathogen.
• The vaccine usually contains a weakened or
dead form of the pathogen it is meant to target.
The body can now produce antibodies against
this weak/dead pathogen so when the fullstrength invader enters the body, it has a
defense ready to combat it. Many vaccines have
to receive boosters occasionally to keep up their
strength.
• Labs are now developing genetically modified
forms of vaccines that can target specific
pathogens and bring about the immune response
in an attempt to keep up with their somewhat
rapid evolution.
Vaccination
Chemical Controls
• Certain chemicals can target specific
pathogens and kill them by not allowing them
to carry out the reactions necessary to survive.
• Antibiotics are chemicals that are obtained
from living things that are toxic to other living
things – often used against predators, prey or
the competition.
• Penicillin was “discovered” by Alexander
Fleming when mould had contaminated an
experiment involving bacteria. He was awarded
the Nobel Prize in Medicine.
• Penicillin interferes with bacterial cell walls –
they become thin and eventually burst under
the pressure of the cell’s own cytoplasm.
Antibiotic Resistance
• Bacteria can reproduce asexually at a
frightening rate – 20 minutes if conditions are
optimal.
• Mutation may occur each time they multiply –
usually it is 1 mutant per 200 bacteria. A
spoonful of dirt may contain over a billion
bacteria – this would yield about 5 million
mutants.
• Some of these mutations give the bacteria the
ability to resist certain antibiotics.
• Canadian hospitals have had bouts with
Clostridium difficile – a bacteria that infects
the colon and releases a toxin inside the body.
It has developed a resistance to many
antibiotics.
Sharing A Problem
• Bacteria can carry out a process called
conjugation with another bacterial cell.
• During conjugation, the bacteria form a tube
(called a sex pilus) between themselves and
exchange copies of their genetic information
called plasmids. These plasmids are the extra
pieces of DNA that often house the genes for
resistance.
• The result may be:
– Bacteria becoming more resistant as the
plasmid is shared throughout the colony.
– Bacteria trading plasmids and, in doing so,
trading resistance genes that will see them
become “super bugs”.
Conjugal Visits?
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