6 Immunity

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  • Created by: Naana
  • Created on: 10-02-15 10:10
What is immunity?
The ability of organisms to resist infection by protecting against disease causing microorganisms they invade their bodies
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What is a pathogen?
Any microorganisms that cause disease e.g. bacteria, fungi and viruses
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What is a non-specific mechanism?
They don't distinguish between different types of pathogens. It responds to all pathogens in the same way and immediately
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What are the two forms of non-specific mechanisms?
A barrier to the entry of pathogens, Phagocytosis
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What is a specific mechanism?
They distinguish between different pathogens. The response is less rapid than non-specific but provides long lasting immunity. The response involves a lymphocyte (type of white blood cell)
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What are the two forms of specific immunity?
Cell mediated response involving T lymphocytes, and humoral response involving B lymphocytes
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Why do lymphocytes have to distinguish between body cells and foreign cells?
So that the lymphocytes don’t destroy the organisms own tissue and so that they can defend the body from invasion of foreign materials
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Are lymphocytes that are involved in the specific immune response produced in response to an infection or do they already exist?
All 10 million lymphocytes already exist. However there are only a few of each type so when an infection occurs, the lymphocytes is stimulated to replicate and increase in number so that there can be effective destruction of pathogen- time lag
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What is the first line of defense against disease?
Forming a physical or chemical barrier to entry. Skin- provides physical barrier that is hard to pathogens to penetrate. Epithelia covered in mucus-pathogens stick to mucus. HCl in stomach-acidic conditions denature pathogens
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What is the second line of defense?
Phagocytosis-Pathogen is recognised as foreign. Phagocytes attach themselves to the surface of the pathogen. Pathogen is engulfed by phagocyte to form vesicle called phagosome. Lysosomes fuse with phagosome. Then, lysosyme break down pathogen
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What does phagocytosis cause at the site of infection?
Inflammation- as a result of the release of histamine which dilutes the blood vessels. This in turn speeds up the delivery of phagocytes to the site of infection
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What is an antigen?
Any part of an organism that is recognised as non-foreign and triggers an immune response (the production of antibodies) by lymphocytes. Usually proteins that are part of the cell surface membrane
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Where are both types of lymphocytes formed and where do they mature?
Both are formed from stem cell. B lymphocytes mature in Bone marrow. T lymphocytes mature in the Thymus gland
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What do T lymphocytes respond to?
Respond to foreign material inside body cells, and respond to own body cells that have been altered by viruses or cancer cells and transplanted tissue (which is foreign as it is genetically different)
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Why can T lymphocytes T distinguish between invader cells and normal cells?
Phagocytes present some of the pathogens antigen on their own cell surface membrane. Body cells invaded by a virus, present viral antigens on their own cell surface membrane. Cancer cells present antigens on their cell surface membrane
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Why is the immune response that T lymphocytes are involved in called cell mediated immunity?
Because T lymphocytes will only respond to antigens that are attached to body cells
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What is humoral immunity?
Immunity involving antibodies that is present in body fluids
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Why are B lymphocytes specific?
There are as much as 10 million different types of B cells. But each type produces a different antibody that responds to one specific antigen
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What happens when an antigen enters the blood or tissue fluid?
There is one type of B lymphocytes that has an antibody on its surface that is complementary to the shape of antigen. When antibody attaches to complementary antigen, B cell divides by mitosis to form clones which will also produce the specific antib
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What do plasma cells do?
Secrete antibodies directly. Only survive for few days but each plasma cell makes around 2000 antibodies per second. Antibodies then destroy pathogen and any toxins. Responsible for primary immune response
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What is the role of memory cells in the secondary immune response?
Circulate in the blood. When they encounter same antigen later, they divide rapidly and differentiate into plasma cells and more memory cells. Plasma cells produce needed antibodies and the new memory cell remain on blood for future infections
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What is antigenic variability?
This is when a pathogen has many different strains. Therefore, the antigens that the pathogen is made of and that they produce constantly change. As a result there will be no antibodies of memory cells formed from previous infections.
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What are antibodies?
A protein produced by B lymphocytes in response the presence of an appropriate antigen. They react with antigens on a foreign cells surface membrane by binding to them precisely(lock and key model). Specific-each antigen has own individual antibody
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What is a monoclonal antibody?
When a single type of antibody is isolated and cloned
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What is a vaccination?
The introduction of a vaccine containing appropriate disease antigen into th3 body (by injection or mouth) to induce artificial immunity
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What is a vaccine?
A weakened form of the pathogen
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How is passive immunity produced?
By the introduction of antibodies into the individual, from an outside source e.g. injection of antibodies. Immunity is generally short lived- as antibodies aren't produced by the individual themselves
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How is active immunity produced?
By stimulating the production of antibodies by the individuals own immune system. Immunity is generally long lasting
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Why do vaccinations rarely eliminate a disease?
Vaccinations fail to induce immunity in people with defective immune systems, pathogen might mutate frequently so antigens change- vaccines become ineffective due to antigenic variability
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Card 2


What is a pathogen?


Any microorganisms that cause disease e.g. bacteria, fungi and viruses

Card 3


What is a non-specific mechanism?


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Card 4


What are the two forms of non-specific mechanisms?


Preview of the front of card 4

Card 5


What is a specific mechanism?


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