Download Infectious Diseases

Infectious Diseases
Topic 6.3 and 11.1
BILL
• Explain the ventilation of the lungs in terms of
volume and pressure changes.
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2.
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6.
7.
As Volume increases, pressure decreases and vice versa
Inhalation causes the diaphragm to contract and the abdominal and
intercostal muscles help raise the rib cage, increasing the volume of the
thoracic cavity
As volume increases, the pressure of the cavity decreases, leading to less
pressure pushing on the lungs
The volume of lung tissue increases, because of the decreased pressure
The pressure inside the lungs now decreases, creating a partial vacuum
Air comes in through the oral/nasal cavity because of the vacuum and
fills the alveoli of lungs with air
Opposite occurs during exhalation, diaphragm relaxes, volume
decreases, pressure increases, and air is force out of the lungs.
6.3.1 Define Pathogen
• Pathogen- any living
organism or virus that is
capable of causing a
disease.
• Pathogens typically include
bacteria, virus, fungi,
protozoa and worms.
6.3.2 – Explain how antibiotics work
against bacteria
• Antibiotics – chemicals that
damage or kill prokaryotic cells,
but not damaging eukaryotic
cells by taking advantage of the
biochemical differences
between the two .
• Common antibiotics work by
blocking cell wall synthesis so
new cells can’t be produced.
• Antibiotics also block protein
production in prokaryotic cells,
but have no effect on eukaryotic
cells
• NO EFFECT ON VIRUS! WHY???
6.3.3 – Outline the role of skin and
mucous membranes in defense
SKIN
• Skin is an obvious barrier to
diseases.
• Made of two layers
• Dermis, bottom layer that
contains sweat glands,
capillaries, sensory receptors
and dermal cells for structure
and strength
• The outer layer, the epidermis,
is primarily dead skin cells,
creates barrier against
pathogens.
Role of Mucous membranes
Mucous Membranes
• Mucous Membranes are types
of tissues that line routes of
entry to the body
• Produces and secretes lining of
sticky mucus to trap pathogens
• Lined with Cilia (hair like
extensions), also trap pathogens
• Secretes Lysozyme, enzyme
that chemically damages
pathogens
6.3.3 Continued, Location of Mucus
Membranes
• Trachea – tube carries air to lungs
• Nasal Passages – tube that allows air to enter
nose
• Urethra – Tube that carries urine from bladder
to the outside
• Vagina – Reproductive tract leading from
uterus to the outside.
Trachea
6.3.4 – Outline how phagocytic leucocytes
ingest pathogens in the blood and in body
tissues.
• Leucocytes (White Blood Cells) – cells in blood stream
used to fight infection and provide an immunity to
many pathogens encountered a second time
– Macrophage – fight pathogens via phagocytosis.
– Protein molecules on the bacterial membrane (antigens)
identify the pathogen as either “self” or “non-self”
– Macrophage will engulf non-self pathogens where
pathogenic remains are digested in lysosome
– This is considered a non specific immune response,
because the identity of pathogen was not determined, it
was simply a non-self molecule.
BILL
• What is an antigen? What is an antibody?
Antigens & Antibodies
• Antigens are proteins embedded in cell
membrane of a foreign invader
• Antibodies are Y-shaped protein molecules
produced in response to specific pathogens
• Antibodies contain binging sites at the end of
each fork, which will bind to Antigens and
attach to pathogen
Antibodies are produced in response
to a specific pathogen
• Leucocytes that produce antibodies are B lymphocytes
(b cells)
– Antigen is first identified
– Specific B lymphocyte is identified that can produce an
antibody which will bind to antigen
– B lymphocytes clone themselves (repeated mitosis) and
increase in number, then begin producing antibodies
– Massive amounts of antibody production
– New antibodies circulate in bloodstream and attach to
antigen, helping to eliminate pathogen
– Some of the new lymphocytes remain in blood stream to
prevent secondary infection – known as memory cells.
Antibody Production
• Problem – leucocytes represent about 1% of
all body cells, so you cannot have enough of
each type of B cell for the amount of antibody
secretion needed.
• Body uses cellular communication to lead to
the cloning of B cells to secrete antibodies
necessary to fight infections
Antibody Production
• Macrophage recognizes pathogen as non-specific “notself ” organism
• Engulfs pathogen by phagocytosis and partially digest it
• Remaining pieces are displayed in manner called
“antigen presentation”
• Leucocytes called Helper T cells recognize the antigen
and turn immune response from non-specific to
specific
• T cells chemically communicate to specific B
lymphocytes, or B cells to produce antibodies
• Each B lymphocyte is capable of producing a specific
antibody which binds to a specific antigen
Antibody Production - Cell Cloning
• When Helper T Cells signal for production of B
lymphocytes, Cell cloning begins
• Clone Two types of cells
– Antibody-secreting plasma cells – cells secret
antibodies immediately to fight primary infection
– Memory Cells – cells do not secrete antibodies,
but have long life in bloodstream waiting for
secondary infection
Primary vs. Secondary response
• Primary Immune Response - occurs the first
time after a body is exposed to an antigen. 1017 days are required for B cells to produce
enough antibodies to help clear antigen
• Secondary Immune Response – occur when
an individual is exposed to an antigen again.
Takes 2-7 days to produce enough antibodies
to help clear antigen.
Principles of Immune Response System
• Challenge and response: Immune system is
challenged by antigen, response by
macrophage, helper t cells, b lymphocytes.
• Clonal Selection: Identification of B
lymphocytes that secrete specific antibody
and multiple cell divisions
• Memory Cells: Cells provide long term
immunity
Polyclonal vs. Monoclonal Antibodies
• Primary immune response (before memory
cells) is a polyclonal response
– This is because the pathogen is being recognized
by many antigens
– Results in clonal selection of many B cells, so
several kinds of antibodies are produced and
several different memory cells are produced
Monoclonal Antibodies
• Procedure used to produce monoclonal antibodies occur
when only one type of antibodies are produced
– Inject antigen into laboratory animal (mouse)
– The animal goes through the primary immune response,
resulting in specific antibodies being produced
– Spleen is harvested and leucocytes that were cloned for injected
antigen are identified
– B cells are fused with cancerous myeloma cells, forming cells
called hybridoma, which produce antibodies and are long lived
– Cells are cultured in separate containers and tested for the
presence of desired antibodies
– An ELISA (Enzyme-linked immunosorbent assay) test identifies
desired B cells, which can be cultured for a long time and
continuously produce desired antibodies
ELISA – Enzyme linked immunosorbant
assay
Uses of Monoclonal Antibodies
• Diagnosis – Pregnancy Tests
– Early in pregnancy, human chorionic gonadotrophin
(HCG) hormone is produced by the embryo.
– Hormone shows up in small amounts in urine and
blood stream.
– Hybridomas can be produced using HCG as an
antigen, and thus producing antibodies that will bind
to HCG
– These antibodies are chemically bound to enzymes
that change color when the antibody binds to HCG,
indicating the presence of an embryo
Uses of Monoclonal Antibodies
• Treatment – Cancer Cells
– Cancer cells produce a specific antigen that can be
used to produce monoclonal antibodies
– Antibodies can be modified to carry a toxin
specific for type of cancer, or a radioisotope for
radiation therapy
– Able to target cancer cell directly, so less toxin and
radiation are needed.
Medical uses of Ab’s
Active vs. Passive Immunity
• Active immunity - described in previous
slides, results in production of memory cells
and provides a long-term immunity to
pathogen
• Passive Immunity – when one organism
acquires antibodies that were produced in
another organism, but no memory cells are
produced
Examples of Passive Immunity
• Transfer of antibodies from mother to fetus through
placenta, so memory cells are not transferred
• Acquisition of antibodies from mother’s colostrum,
which is the breast milk produced in late pregnancy
and the first days after birth. Colostrum is high in
antibodies
• Injection of antibodies in antisera (antivenoms for
snake/spider bites). Venom is a protein that can illicit
antibody production, but primary response is typically
too slow and would result in massive damage, so
antivenoms are used.
BILL
• What is the difference between active and passive immunity?
What is an example of passive immunity?
• Active immunity occurs when a body is challenged by an antigen,
responds with clonal selection and the production of memory
cells
• Passive immunity occurs when the body gets antibodies that
were produced by another organism and no memory cells are
formed.
• Transfer of antibodies through placenta from mother to offspring,
or transfer from colostrum (breast milk) to offspring
• Anti-venom is used to treat bites from venomous snakes/spider
11.1.1 Describe the process of blood
clotting
• When your skin is punctured, typically you
puncture the capillary bed that is delivering blood
to that area. With that, you release blood
(remember—capillary walls are only 1 cell thick)
• The plasma portion of your blood contains many
different proteins that are involved in the
clotting. The clotting of blood stops blood loss
and prevents pathogens from entering body.
Blood Clotting – platelets stick together to
damaged/torn area and seal the “leak”
 If wound is more serious  clotting process
takes over
1. Platelets release thromboplastin (clotting factors)
2. Thromboplastin converts prothrombin (plasma
protein) into thrombin
3. Thrombin converts fibrinogen into fibrin
4. Fibrin forms a network of strands that trap RBCs and
platelets to form clot
5. Once the healing is complete, plasmin (enzyme)
dissolves the fibrin clot
Blood Clotting
Viruses
• Pathogens that consist of nucleic acid, a protein coat,
and in some cases, a membranous envelope
• May have double or single stranded DNA, double or
single stranded RNA
• Protein shell is called a capsid
• Viruses can only reproduce within a host cell
– Lytic cycle – reproductive cycle that breaks down hosts
DNA, uses it to produce proteins and nucleotides, and
destroys host cell at end of cycle
– Lysogenic cycle – reproductive cycle that integrates viral
DNA into host DNA, forming a prophage, DNA is replicated
normally, producing a colony of prophages, or can initiate
lytic cycle at a later time.
Viruses
• Bacteriophage – virus that infect bacteria
• Eukarytotic viruses – diverse and dependent
on type of nucleic acid found inside
How HIV Damages the immune system
• Viruses need a type of cell that is complementary
to own proteins
• Depending on the cell it infects, different viruses
can have different symptoms/severities
• Human immunodeficiency virus (HIV) is the virus
that eventually leads to AIDS (acquired immune
deficiency syndrome.
• HIV infects Helper T cells – cells that
communicate which B cells need to undergo
cloning and produce antibodies.
T-Helper Cells
• HIV infects T-Helper cells of the immune system.
• Helper T cells help identify which antibodies need
to be produced. Frequently, the virus will go
undetected for years (virus has a latency period).
• HIV is a retrovirus - A retrovirus is an RNA virus
that is replicated in a host cell via the enzyme
reverse transcriptase to produce DNA from its
RNA genome. The DNA is then incorporated into
the host's genome by an integrase enzyme.
HIV Damages Immune System
• When helper T-cells begin to die  no
communication between cells  no
antibodies produced
• Individual no longer fights off pathogens and
symptoms of AIDS appear
• Secondary infections ultimately take the life of
someone with AIDS
Once detected, HIV mutates incredibly fast so it
is very difficult to treat with medications.
Why is HIV/AIDS Difficult to treat
• Virus can be hidden in body cells for years
because of latency period
• Virus mutates relatively quickly, vaccines may
not recognize/affect it after several mutations
• Association w/ Sexual Activity & Drug abuse
led to reluctance in funding
Vaccinations
• Bodies cannot be immune to a pathogen they
have not been exposed to.
• Vaccines act as first exposure
– Pathogen is weakened by exposure to heat or
chemical treatment
– Leucocytes respond to “not-self” pathogen and
primary immune response occurs
– Memory Cells form capable of producing
antibodies if there is a real infection
Vaccinations
• Do not prevent infection but speed up
secondary response of immune system
compared to primary response
Benefits and Dangers of Vaccinations
Possible total elimination of disease. This
has occurred with smallpox and many
people believe it is possible to eradicate
both polio and measles
Prior to 1999, many vaccines contained
thimerosal, a mercury based preservative.
Mercury has been shown to be a neurotoxin
to which infants and young children are
susceptible.
Decrease in the spread of epidemics
(localized infections) and pandemics
(worldwide infections) Increased
international travel has made this more
important than ever because of how easily
infections can travel
Preventative medicine is typically the most
cost effective approach. Costs associated
with vaccinations are small compared to
costs of treating preventable diseases
The perception exists that multiple vaccines
given to children in a relatively short period
of time may overload their immune system
Each vaccinated individual benefits because
the full symptoms of the disease do not
have to be experienced to gain immunity.
Cases have been reported of vaccines leading
to allergic reactions and autoimmune
responses.
Anecdotal evidence that suggest MMR
(measles, mumps, rubella) vaccine may have
a link to onset of autism. No clinical studies
support this
Exercises
• When a person is bitten by a poisonous snake, they are given
an antivenom. The antivenom is composed of antibodies
which recognize protein molecules on venom and bind to
them. This type of treatment is referred to as passive
immunity and does not confer long term immunity. Why is
that?
• Why are some viruses potentially lethal, while others cause
fairly mild symptoms?
• Describe how skin and mucus membranes act as barriers to
pathogens?
Antivenom
• Antibodies produced by another organism.
The memory cells that are capable of
producing these antibodies are located in the
organism that produced them, not in the
organism who receives the antivenom. Long
term immunity comes from memory cells. This
is called passive response
Severity of Symptoms
• Severity of symptoms depends on two factors:
– Tissue type that is the target of a particular virus,
some tissue types are potentially more dangerous
when infected
– How quickly virus replicates could result in less
time the immune system has to respond
Skin/Mucous Membrane Barriers
• Skin is a physical barrier to entry, dry skin
inhibits growth of bacterial cells; bacteria on
skin prevents growth of other bacterial cells;
sweat contains anitmicrobial/lysozyme to
keep bacterial growth in check
• Mucous Membrane traps bacteria in sticky
mucus; cilia sweep/trap bacteria; secretes
lysozyme to destroy bacteria; contain
macrophages to perform phagocytosis