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Defense Against Infections Disease
Topic 11.1 (and 6.3)
Blood ClottingWhen blood vessels get broken, blood is able
to escape from the closed circulatory system and pathogens have a way to enter the body.
To prevent excessive blood loss and the entry of pathogens, a clot will form to seal the damaged blood vessels.
Blood ClottingThere are a few components in your blood
that are important for blood clotting:
1)Prothrombin and Fibrinogen These are plasma proteins Always present in blood but inactive unless
you start to bleed
Blood Clotting
2. Platelets Small, irregularly shaped blood cells made in
bone marrow They start as large cells, and then break into
many smaller fragments No nucleus Live only 8-10 days
Blood Clot1) A cut occurs damaging a small blood vessel
2) Blood (including rbc, wbc, plasma proteins and platelets) will ooze out of the cut.
3) The damaged tissues will release chemicals that will cause platelets to adhere to each other and the damaged area causing a plug.
Blood Clot4) The platelets and damaged tissue will release
clotting factors which include the enzyme thrombokinase.
5) Thrombokinase will catalyze the conversion of prothrombin (a plasma protein) into the enzyme thrombin
6) Thrombin will catalyze the conversion of soluble fibrinogen (a plasma protein) into insoluble fibrin
Blood ClotFIBRIN:
A fibrous protein which forms a mesh-like network that helps to stabilize the platelet plug
7.More cellular debris will become trapped in the fibrin mesh and a stable clot will form preventing further blood loss or the entry of pathogens
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Lymphatic SystemThe lymphatic system transports a watery,
clear fluid known called lymphThe lymph distributes leucocytes (wbc) and
other factors throughout the body. It also interacts with the circulatory system
to drain fluid from cells and tissues and remove foreign invaders and microorganisms.
It contains lymphocytes that protect the body against antigens by producing antibodies
Lymph nodes are small ball-shaped organs throughout the body, and part of the lymphatic system.
They become enlarged when there is an infection because an increase in T and B lymphocytes.
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The Immune Response & Antibody ProductionWhen a pathogen enters your body, the
immune system will try to get rid of it.
Remember, your leukocytes recognize cell surface proteins (antigens) and can determine if a cell is “self” or “not self
“self”= body cell“not-self” = a foreign cell
(Remember, there are lots of different types of leukocytes.)
The first type of leukocyte that will encounter a pathogen is usually a macrophage.
The macrophage will ingest the pathogen through phagocytosis and partially digests it.
The macrophage will take the antigens of the pathogen and display on its own cell membrane
This is known as antigen presentation
The macrophage will then go to the lymph nodes
In the lymph node, the macrophage will present the antigens to various types of helper-T cells (TH)
Helper-T cells are a types of lymphocytes
A helper-T cell with receptors on its membrane that are complementary to the antigen will be selected. (They basically take an imprint of the antigen)
These helper-T cells will undergo mitosis to make clones of itself.
The helper-T cells will then go to a B lymphocyte (also called a B cell)
B lymphocytes make antibodies
The B cell will identify the blueprint of the antigen and make antibodies against the antigen that can be released and attach to the antigens of the pathogen
When a B cell is activated, it will also undergo mitosis to make clones of itself
It will make plasma cells and memory cells
Types of B LymphocytesPlasma cells (Plasma B cells):
these cells will make antibodies immediately to fight off the infection
Memory Cell (Memory B Cells):These cells do not secrete antibodies during the 1st
infection.They are long-lived cells which will remain
circulating in the bloodstream If the individual becomes infected with the same
pathogen, the memory B cells will be ready to release antibodies against the pathogen
NoteWhen the macrophage displays the antigens
on its cell membrane, the antigens are attached to MHC proteins (major histocompatability complex proteins)
Helper T-cells will only respond to antigens attached to MHC proteins
Cytotoxic T-cells or Killer T-Cells are another type of lymphocyteThey recognize cells that have been invaded by
pathogens and will destroy these cells.
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http://highered.mheducation.com/sites/0072943696/student_view0/chapter14/animation__t-cell_dependent_antigens__quiz_1_.html
http://highered.mheducation.com/sites/0072943696/student_view0/chapter14/animation__the_immune_response.html
Antigen formation (advanced) http://highered.mheducation.com/sites/0072943696/student_view0/chapter
14/animation__antigen_processing.html
ImmunityACTIVE IMMUNITY:
Due to the production of antibodies by the organism itself after the introduction of antigens
PASSIVE IMMUNITY:Due to the acquisition of antibodies from another
organisms in which active immunity has be stimulated
Ex: from mother to fetus via the placenta or breast milk
Ex: the injection of antibodies (often used as treatment after a snake or spider bite)
Active Immunity can be…..
NATURAL IMMUNITY:Antibodies are present because the individual
naturally came into contact with the pathogen
ARTIFICIAL IMMUNITYAntibodies are present because the individual
was given a vaccine and introduced to a weak or dead form of the virus
Monoclonal Antibody ProductionThe primary immune response of an
organism is called a polyclonal response.This is because the pathogen will have many
type of antigens on its cells surface , not just one.
So several kinds of plasma B cells will go under clonal selection to produce several kinds of antibodies
After a polyclonal immune response, it is difficult to separate the different kinds of antibodies
Monoclonal Antibody ProductionHow are monoclonal antibodies obtained?
1)A mammal (i.e. a mouse) is injected with a particular antigen
2)The mouse’s plasma B cells will produce antibodies against the antigen
3)The plasma B cells are extracted and fused with a B-cell tumour cell (a rapidly dividing B-Cell) to create a hybrid called “hybridoma cells”
4)Hybridoma cells grow in culture producing identical antibodies that can be collected
Use of This TechnologyBlood Type TestsPregnancy TestsTests for diseases and infections
Ex: Pregnancy TestsRemember, when a woman is pregnant she
secretes the (protein) hormone HCG (human chorionic gonadotropin) in her urine
The antibodies for HCG can be fixed to a testing strip
If a woman is pregnant, the HCG in her urine will attach to the antibodies on the testing strip
The test is designed to produce a specific colour (or shape) to indicate a positive test
Monoclonal Antibodies as Treatments
When body cells become cancerous, they begin to produce specific antigens on their cell membrane
A possible treatment for cancer is to produce monoclonal antibodies that target the cancer-cell antigens
The antibodies could be modified to carry a toxin to those cells or a radioisotope to mark the cells for radiation therapy
VaccinationThe secondary response to an antigen is must
faster than the first response
Vaccinations deliberately expose an individual to a weakened/dead/similar pathogen
In this way, the individual can create memory B cells against the antigens of the pathogen and be prepared for an infection
If the individual comes into contact with the pathogen after vaccination, they will have a faster immune response and will likely avoid illness
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Benefits of VaccinationsEradication of some diseases (e.g. small pox)Fewer people get the diseases (because
already have the antibodies)Prevents disability and other effects of the
pathogenEx: polio can cause paralysis (no polio, no polio
related paralysis)Herd immunity
If many people in the population are vaccinated, the disease will not spread and there will be a decreased chance that someone who did not get the vaccine will contract it anyway
Dangers of VaccinationOverloading the immune system with
antigens will reduce the ability to handle other infections
Other pathogens could grow in the solution with the vaccine
The vaccine could have other harmful substances (often added to increase shelf life of vaccine)
Artificial immunity is less effectiveDiseases avoided as a child are more serious as
an adultEx: chicken pox in adults can result in shingles
Side AffectsEx: Suggested an increase chance of autism
(not confirmed)Can lead to allergic reactions and autoimmune
responses
