Download TOPIC 11.1

TOPIC 11.1
Defence Against Infectious Disease
11.1.1
Describe the Process of Blood Clotting
• Proteins floating in blood plasma
assist in blood clotting:
– Prothrombin
inactive unless bleeding occurs
– Fibrinogen
– Platelets formed in bone marrow (small sticky cell fragments)
• What happens when a small blood vessel is
damaged (we get cut)?
1. Damaged cells release chemicals which stimulate
platelets to adhere (stick) to the damaged area
2. This forms a plug
3. Platelets release clotting factors which convert
prothrombin to thrombin
4. Thrombin is an enzyme which catalases the
conversion of fibrinogen to fibrin (fibrous protein
which forms a mesh-like network
5. More and more platelets and cellular debris become
trapped in the fibrin and form a clot which closes the
wound and prevents pathogens from entering the
body
More important factors in blood clotting
• Vitamin K is required for the production of
prothrombin
• Ca2+ ions are necessary for the conversion of
prothrombin to thrombin
• Many proteins (clotting factors) are necessary:
– Enzyme thrombokinase along with factors X and VII
and Ca2+ ions are all necessary for the conversion of
prothrombin to thrombin
– Factors XII, XI and IX are necessary for the activation of
factor X
11.1.2
Challenge and Response, Clonal Selection and
Memory Cells as Basis of Immunity
• Challenge and Response:
– When a pathogen invades the immune system is
challenged and will produce antibodies against the
invading pathogen as a response
– Leucocytes, called B lymphocytes, produce antibodies
– Macrophages (phagocytes) travel to lymph nodes along
with fragments of cell walls or membranes of pathogens
– Lymph node cells (lymphocytes):
• Helper T-cells identify the antigen and activate the correct
B-cells to begin a series of cell divisions
• We have many types of T-cells and B-cells, but not many of
each type unless activated to clone themselves
• Clonal Selection:
– Refers to the process of the macrophage selecting which
T-cells and B-cells have the required surface receptor
proteins complimentary to the antigen
– Clones of the appropriate T-cells and B-cells are formed
by mitosis to produce large numbers of cells required to
deal with the infection
– B-cells will differentiate into plasma cells and memory
cells
– Plasma cells will produce antibodies
• Memory Cells
– Long-lived cells which remain circulating in the
bloodstream waiting for the next infection. These are
only produced after exposure to a pathogen.
11.1.3
Define Active and Passive Immunity
• Active Immunity:
– Immunity due to the production of antibodies after the
body has been challenged by the presence of an antigen
– Production of memory cells leading to long-term, full
immunity
– ex. vaccination or having the illness
• Passive Immunity:
– Immunity due to the acquisition (acquiring, getting)
antibodies produced by another organism
– No memory cell production, short-term immunity
– ex. mother to fetus via placenta, mother to infant via
colostrum (breast milk)
11.1.4
Explain Antibody Production
• Pathogens typically have many different antigens in
their walls or membranes (not just one)
• The response to these pathogens is called polyclonal
(many different plasma B-cells are cloned)
• Summary:
1.
2.
3.
4.
Macrophage brings antigen to lymph node
T-cell activates correct B-cell
T-cells and B-cells clone themselves
B-cells produce plasma B-cells (which produce antibodies)
and memory B-cells (which are long-lived and protect
against future exposure)
11.1.5
Production of Monoclonal Antibodies, Their
Use in Diagnosis and Treatment
• Monoclonal = one, pure type of antibody
• How to Produce Monoclonal Antibodies??????
1. Inject an antigen into lab animal (mouse)
2. After mouse has gone through immune response and
produced antibodies, extract mouse plasma cells
3. Fuse these antibody containing mouse B plasma cells
with tumour cells (called hybridoma cells)
4. Allow to grow and produce the antibody
5. The hybridoma cells produce antibodies (B plasma
cells) and are long-lived (tumour cells)
• Using Monoclonal Antibodies for Diagnosis:
– Pregnancy testing
– Determining blood types (A, B, AB or O)
• Using Monoclonal Antibodies for Treatment:
– Creating monoclonal antibodies for cancer cell
antigens (cancer cells produce specific antigens not
present in normal cells)
– Advantage to this treatment is that these antibodies
could target only specific cancer cells
11.1.6
Explain the Principle of Vaccination
• Inject someone with a weakened/dead/related
pathogen to stimulate the immune response
• As a result the person will produce B plasma cells
(which produce antibodies) and B memory cells
(which provide full, long-term immunity)
• ex. Bacterial diseases: diphtheria, whooping
cough, tetanus, and Viral diseases: measles, polio,
rubella, small pox
11.1.7
Discuss Benefits and Dangers of Vaccinations
Benefit
Danger
Possible total elimination of the disease.
ex. small pox, and hopefully polio and
measles
Prior to 1999, many vaccines contained
thimerosal, a mercury-based preservative.
Mercury is a neurotoxin particularly to
infants and children.
Decrease in spread of epidemics (local
infections) and pandemics (worldwide
infections).
Perception exists that multiple vaccines in
a relatively short period of time
(childhood)may “overload” the immune
system.
Preventative medicine is the most costeffective approach to healthcare.
Vaccination costs are small compared
with treatment for these diseases.
Anecdotal evidence suggests that MMR
(measles, mumps and rubella) vaccine
may have a link to autism. Anecdotal
means based on a small sample. This is
NOT supported by clinical studies.
Each individual benefits by not having to
have the disease to obtain future
immunity.
Cases have been reported of vaccines
leading to allergic reactions and
autoimmune responses.