Download Defence Against the Dark Arts..... or Infectious Diseases

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 Burkitt’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.
 Ie: 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 (ie 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 (ie:
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 an 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)
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
viral and bacterial invaders.
 The skin provides a physical barrier like a wall
preventing pathogens from getting in.
 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.
 Acidic secretions (pH 3-5) inhibit 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 may help in these areas to trap micro-
organisms and prevent further entry
 Examples….
 In the trachea (which leads to the lungs), foreign particles
are trapped in mucous or filtered by tiny hair-like
structures called cilia that sweep particles to the entrance
where coughs can expel them.
Mucous Membranes
 In the stomach, corrosive acids and digestive enzymes
destroy microbes that may be found in food.
 The vagina produces mucous and has an acidic
environment too
 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
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.
 This will make the
foreign invader useless
and target it for
phagocytosis
HIV and the Immune System
 HIV: human immunodeficiency virus is a virus that
infects the cells of 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.
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.
AIDS
 HIV can lead to AIDS (aquired 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
AIDS 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 thery 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