Transcript Lesson 1

Topics 6.3 & 11.1
The Boy in the Bubble
 David Vetter = born Sept 1971
 His parents had a first son (also named David) that
was born the year before, but died after 6 months
because of SCID – severe combined
immunodeficiency
 SCID – body is unable to produce wbc to fight off
foreign invaders
 The disease is X linked, meaning that there is a 50%
chance that a Vetter male child would have SCID
 When their second son David was born, he also had
SCID and was placed in a “plastic bubble” 10 seconds
after birth to keep him in a sterile environment away
from foreign invaders.
 He lived in the bubble for 12 years
 Doctors hoped to cure him with a bone marrow
transplant from his healthy sister.
 Unknown to doctors, Katherine had a virus in her
marrow.
 When David received the transplant, the virus caused
mononucleosis, and eventually grew out of control and
lead to Burkett's lymphoma (a type of cancer)
 Knowing that he was dying, he spent his last few days
of life outside the bubble.
 http://www.bing.com/videos/search?q=boy+in+the+bubble+disease&FORM=HDRSC3#
view=detail&mid=4FD8CDA29BAB681AF9F44FD8CDA29BAB681AF9F4
Pathogen
 A pathogen is an organism or a virus that causes a
disease in any other organism.
 I.e.: Bacteria, fungi, viruses
 Exposure to the majority of pathogens does not result
in a disease because
 We can prevent pathogens from entering our bodies
 We can develop an immunity to particular pathogens
 We can use chemicals (i.e. antibiotics) to defend
ourselves.
Viruses
 Non cellular structures
 Contain DNA or RNA surrounded by a protein coat.
 Not considered to be a living cell because they cannot
undergo essential life process on their own (i.e.:
replication or protein synthesis)
 (When a virus wants to replicate, it enters an
(unwilling) “host” cell and uses the host’s enzymes to
replicate its DNA. It takes away energy and resources
from the host cell.)
HPV
EBOLA
Polio
Rabies
Viruses and antigens
 Viruses will have antigens on its protein coat/cell
membrane.
 All viruses must find a type of cell in the body that
matches their own proteins in a complementary way so
it can enter the cell (through endocytosis)
 This is why only certain body cells are damaged by
certain viruses as is typically reflected in the symptoms
associated with the infection.
Bacteria
 Prokaryotic cells, that can rapidly duplicate
 A colony of bacteria can obstruct regular function in
the host organism
 Bacteria products can cause unpleasant side-affects to
a host organism.
Streptococcus
H. pylori
Antibiotics
 Antibiotics are chemicals that may be used to fight off
bacterial infections.
 Antibiotics often work by disrupting the ability of the
bacterium from replicating and/or undergoing protein
synthesis.
 (If they cannot undergo protein synthesis, they will lack
the essential proteins for life – and thus die)
 (If they cannot replicate, the colony will not be able to
increase in number and eventually the body’s immune
system will be able to kill the remaining bacteria)
Antibiotics
 Antibiotics do not disrupt cell function in your cells
because bacteria cells are prokaryotic and you are made of
eukaryotic cells.
 They are different enough that it doesn’t have an effect on
your cells.
 Why can’t antibiotics be used to kill viruses?
 Viruses don’t undergo replication or protein synthesis on
their own so there is nothing to disrupt.
Antibiotics
 Antibiotics are often derivatives of fungus such as
penicillin (which comes from the fungi Penicillium)
 If fungi and bacteria are competing for the same food
source, and the food source becomes scarce
penicilllium will release antibacterial antibiotics
(penicillin)
Testing Penicillin (p307)
 In 1928, Scottish scientist Alexander Flemming
(accidently) discovered penicillin.
 In the 1930’s, scientists Howard
Florey and Ernest Chain investigated
the use of penicillin.
Testing Penicillin
 Penicillin killed bacteria on agar plates but they
wanted to know if it could be used to control bacterial
infections in humans.
 They first tested it on mice
 8 mice were deliberately infected with a streptococcus
bacteria that causes death from pneumonia.
 4 of the mice were given penicillin injections.
 Within 24 hours, the 4 untreated mice were dead but
the 4 given penicillin were healthy.
(2) 4 of the mice
were given
penicillin. The other
4 were not. 
(1) 8 Mice are given
streptococcus
24 hours later….
(3) The mice given
penicillin recovered and
lived.
The mice that were
untreated died. 
Testing Penicillin
 They next conducted human trials.
 The 1st human test subject was a 43 year old male with
an acute, life-threatening bacterial infection
 He was given penicillin for four days and his condition
improved considerably.
 Unfortunately, supplies of penicillin ran out and he
suffered a relapse and died from the infection.
Testing Penicillin
 Larger quantities of penicillin were produced and they
tested it on 5 more patients with acute infections.
 All were cured of their infection.
 (Unfortunately, one of the patients died from a brain
hemorrhage brought on by complications from the
initial infection, however, the infection was cured)
 Pharmaceutical companies in the US began producing
penicillin in larger quantities allowing for more
extensive studies, confirming it’s use as a highly
effective treatment for previously incurable bacterial
infections
Testing Penicillin p 308
 Florey and Chain’s test on the safety of penicillin
would not be compliant with current testing protocols.
 They tested the drug on human patients after a very
brief period of animal testing – there could have been
severe side effects
 The samples they used were not pure and there could
have been side effects from the impurities.
Testing Penicillin p308
 On the other hand, the subjects they used all had
severe infections and were on their death beds.
 They were cured as a result of the experimental
treatment.
 And because of the expeditious, risk-taking testing,
penicillin was used to treat wounded soldiers on DDay (June 1944) and the number of deaths from
bacterial infections was greatly reduced.
Resistance to Antibiotics
 Some strains of bacteria have evolved genes giving
them resistance to antibiotics and some strains of
bacteria have multiple resistance.
 If a bacterium is resistant to one antibiotic, its not too
big of a problem.
 If a strain develops multiple resistance, that can be
concerning.
How to Prevent Antibiotic
Resistance
 Antibiotics should only be prescribed for serious
bacterial infections.
 Patients must complete the prescribed course of
antibiotics to eliminate infections completely.
 High standards of hygiene require at medical facilities
to prevent cross-infection.
 Farmers shouldn’t use antibiotics in animal deeds to
stimulate growth
 Pharmaceutical companies need to develop new types
of antibiotics (*no new types have been introduced
since 1980s)
Fungi
Parasites
1st Line of Defense
 The first line of defense against foreign invaders is
mainly physical
 The skin and the mucous membranes defend against
foreign invaders.
 The skin provides a physical barrier like a wall
preventing pathogens from getting in.
The Skin
 The epidermal layer is constantly being replaced as
underlying dermal cells die and are moved upwards.
 The epidermal layer is mainly dead cells and thus is a
good barrier because it is of no use to viruses.
Sebum
 The sebaceous glands produce a chemical called
sebum
 The sebum provides moisture
 It is also an acidic secretions (pH 3-5) which inhibits
the growth of microbes
Mucous Membranes
 Weak points in our defense against foreign invaders
are areas in which we are not protected by skin.
 Mucous membranes secrete a mucus, which is a sticky
solution of glycoproteins.
 Mucus may help in these areas by trapping micro-
organisms and prevent further entry
Examples (Mucous Membrane)
 In the trachea (which leads to the lungs), foreign
particles are trapped in mucous or filtered by tiny hairlike structures called cilia that sweep particles to the
entrance where coughs can expel them.
 In the stomach, corrosive acids and digestive enzymes
destroy microbes that may be found in food
Mucous Membranes
 The head of the penis, and the inner layer of foreskin
have mucous membranes.
 The vagina produces mucous and has an acidic
environment too to protect itself.
 Lysozyme – an antimicrobial enzyme that is found in
tears, saliva, mucous secretion, perspiration will
destroy bacterial cell wall killing the bacteria.
nd
2
line of Defense
 Kicks in when the invader takes up residence with in
the body.
 INFECTION: the successful invasion of a pathogen
 Leukocytes are used to fight off an infection
 (There are different types of leukocytes. Leukocytes
that create make antibodies are called lymphocytes.)
Leukocytes
 are white blood cells (wbc)
 Found in the blood stream but also in body tissues
 have a nucleus unlike rbc
 responsible for responding to foreign invaders and
destroying them
 many different types
Bone
Marrow –
where
blood cells
are made
Carry O2 to cells
Produce
antibodies
Find
invaders
and
initiate
attack
Involved in
blood
clotting
Macrophage
 Is a type of wbc that ingests foreign invaders by





phagocytosis
(Because it undergoes phagocytosis, it is also referred
to as a phagocyte)
All cells have proteins on their cell membranes called
ANTIGENS
Antigens act as identity markers.
Macrophages recognize body cells of the host by its
antigens
Foreign invaders will have different cell surface
antigens which will cue macrophages to get rid of
them
Phagocytosis
 This is the process when wbc ingest invading microbes
and chemically destroy them with enzymes
 Macrophages –have pseudopods which are protrusions
that will attach to the surface of an invading microbe,
engulf it and digest it with enzymes
 This is a non-specific immune response because the
identify of the pathogen is not determined (at this
point)
Animations
 http://www.pennmedicine.org/encyclopedia/em_Disp
layAnimation.aspx?gcid=000098&ptid=17
Antibody
 Also known as an immunoglobulin
 Soluble proteins that are produced by the immune
system as a response to the presence of an antigen
 Many different types.
 Produced by different kinds of lymphocyte (each
lymphocyte will recognize a particular kind of antigen
and produce antibodies against that kind of antigen)
Antibodies
 Attach themselves to
antigens of foreign
invaders.
 How does this help
destroy pathogens?
Role of Antibodies
 Neutralization of
pathogens
 This will make the
foreign invader useless
because now they cannot
enter host cell (cannot
“dock” on host cells
 Also can neutralize
toxins produced by
pathogens
Role of Antibodies
 Opsonization
 Antibodies target
pathogens for
phagocytosis (by
phagocytes)
Role of Antibodies
 Agglutination
 The “clump” of pathogens cannot enter a host cell
 Easier target for lymphatic system to filter and
phagocytes to ingest.
Role of Antibodies
 Activation of Complement
 The complement system is a collection of proteins which
ultimately lead to the reformation of the membranes of
pathogens.
 Antibodies attach to the surface of antigens causing a
pore in the membrane
 Water and ions enter the cell causing the cell to swell
and lyse
HIV and the Immune System
 HIV: human immunodeficiency virus is a virus that
infects the cells of the immune system
 It is a retrovirus: it contains
RNA and when it enters a host
cell it uses the enzyme reverse
transcriptase to make DNA
from the RNA.
HIV and the Immune System
 It reduces the number of lymphocytes that are actively
involved in the production of antibodies
 Leads to less antibodies which means the individual
will be more likely to develop a disease that would be
easily fought off by a healthy immune system
HIV
 Hard to find a cure or a vaccine.
 HIV hides in its host cell for years
 Mutates relatively quickly – always changing its
antigens making it hard to vaccinate against and hard
for body’s immune system to recognize it.
 The rate of which HIV destroys lymphocytes can be
slowed down with antiviral drugs
AIDS
 HIV can lead to AIDS (acquired immune deficiency
syndrome)
 In these cases, HIV has severely weakened the
individual’s immune system and their lymphocyte
count is particularly low.
 These individuals are susceptible to illnesses that
healthy individuals have no problem fighting off such
as the common cold
HIV transmission
 Through:
 Blood
 Semen
 Vaginal secretions
 Breast milk
 Most common transmission occurs via:
 Unprotected sex
 Sharing of injection needles
 Mother to child during birth or breastfeeding
HIV animations
 http://highered.mheducation.com/sites/0072943696/
student_view0/chapter14/animation__hiv_replication.
html
 http://highered.mheducation.com/sites/0072943696/
student_view0/chapter14/animation__how_the_hiv_i
nfection_cycle_works.html
Social Implications of AIDS
 In 2006, more than 60% of people living with
HIV/AIDS were from Sub-Sahara Africa.
 Of the 3 million people who died from AIDS related
diseases in 2006, 2 millions of them were from SubSaharan Africa
 The number of new infections in North America and
Western Europe have either stayed the same or decreased.
 This is believed to be the result of HIV prevention
programs and education
 Lack of these programs in Sub-Saharan African is likely the
reason why HIV/AIDS is not declining in this areas
Social Implications
 People with HIV/AIDS can suffer from stigmas and
discrimination
 Women are more likely to contract HIV from sex with
an infected partner than men.
 People who die from HIV/AIDS are often at an age
where they are the most productive members of
society – removing individuals from the work force
and delaying economic growth, an creating orphans
Social Implications
 Unemployment  poverty  cannot afford
treatments
 Poverty increases the chances of contracting
HIV/AIDS due to lack of education on safe sex and
increased prostitution
 Neutrophils – attracted to chemical signals given off by
wbc damaged by microbes.
 They migrate toward infected tissue and engulf the
microbe and wbc
 This creates pus – which is fragments of proteins and
dead wbc and the digested microbe.
 When tissue is damaged because of physical injury the
body responds with localized inflammatory response:
swelling, heat, redness, pain
 If pus is present too, its a sign that the second line of
defense has been at work
 Fever – this is the body’s response to infection
 When chemicals released by wbc reach the
hypothalamus relaying information that the body is
fighting off an infection, the hypothalamus’ response
is to raise body temperature to ~40°C
 These conditions make it harder for the invader to
survive and reproduce
 Some believe taking meds to reduce fever may prolong
infection
 But high temperatures can be dangerous to humans
who’s cells can’t survive above 43°C