Unit 3.2.6 - The Bodies Defense System Flashcards
What on pathogens trigger an immune response?
The foreign antigens on its surface
What is an antigen?
A large complex molecule that triggers an immune response - like a glycoprotein
What is an antibody?
A protein secreted by B cells in response to a non-self antigen
Describe the structure of an antibody?
Four polypeptide chains joined together by disulphide bond, two of the chains are long heavy longs and two of the chains are short lighter chains.
What is the same about all antibodies?
The constant region
What is different between all antibodies?
The variable region
What is the shape of the variable region determined by?
The sequence of amino acids which make up the primary structure of the protein
Draw the structure of an antibody?
See flash card 21
What type of white blood cell carries out phagocytosis?
A phagocyte
What are the five steps in phagocytosis?
- ) The phagocyte recognises the foreign antigens on the pathogen
- ) It moves its cytoplasm around the pathogen engulfing it in a phagosome
- ) A lysosome fuses with the phagosome
- ) It releases lysosomal enzymes
- ) These enzymes begin to break down the pathogen
What is the pathogen contained in during phagocytosis?
A phagosome
How do phagocytes activate T cells?
After phagocytosis they present the foreign antigens on their surface which activates the T cells
Name two other types of white blood cells, not including phagocytes?
B cells and T cells
What type of response do the T cells form?
The cellular response
What type of response do the B cells form?
The humoral response
What cells form the cellular response?
T cells
What forms the humoral response?
B cells and the production of antibodies
What are the two types of T cells?
Killer and helper cells
What do the killer T cells do?
They attach to antigens on the pathogen and kill the cell
What do helper T cells do?
They activate the B cells
How do B cells becomes activated?
They have antibodies on their surface, when they bind with foreign antigens they form antigen-antibody complexes and so become activated
When the B cells become activated what cells do they produce and how?
They divide by mitosis, so that the new cells are genetically identical and have the same antibodies which are specific to the antigens on the pathogen, these are called plasma cells
What three ways do antibodies help the immune response?
- ) coating the pathogen to make it easier for the phagocyte to engulf
- ) coating the pathogen to prevent it from entering host cells
- ) bind to and neutralise toxins produced by the pathogens
What do both B and T cells produce which mean you become immune to a pathogen after coming in contact with it?
Memory cells
Why do memory cells mean you are immune to a pathogen?
If you ever come in to contact with the same antigen again they recognise it and produce plasma cells much faster than before so you don’t get ill and so you are immune
What type of response are plasma cells known as?
Primary response
What type of response are memory cells known as?
Secondary response
If the primary or secondary response slower and why?
Primary because there aren’t many B cells making the correct antibody so they have to divide which all takes time
Why are you usually given a second injection?
To boost the number of memory cells in your blood so that you can still quickly produce plasma cells to fight of the pathogen
What is meant by antigenic variation?
When pathogens can change their antigens on their surface
What is bad about antigenic variation?
If the antigens change it means you will no longer have memory cells that will recognise the pathogen and so you will no longer be immune
Why do you have to have a new flu vaccination each year?
The influenza virus shows antigenic variation and so the antigens keep changing so even though you have memory cells for the pathogen one year they may have changed by the next so you need a new vaccination
What is a vaccine?
It is when dead or weakened pathogens or antigens are put into the body (often by an injection) to provide protection for individuals and populations against disease
Describe how a vaccine gives you immunity to a certain pathogen?
When the body comes into contact with the foreign antigens it activates the T cells which then activate the B cells
The B cells then divide to produce plasma which they produce antibodies to destroy the pathogen
Memory cells are also produced by the B and T cells so that the secondary response happens much faster and you don’t get ill from the pathogen and so are immune
What is herd immunity?
When a high percentage of the population is vaccinated so that there are fewer people to carry the disease and pass it on so fewer people will develop the disease
What is a monoclonal antibody?
An antibody that is specific to one particular antigen and can be mass produced for medical purposes
How can monoclonal antibodies be used to treat cancer?
You can attach anti-cancer drugs onto the end of the monoclonal antibodies, this means when the antibody binds to the specific antigens on the surface of the tumour the drug can be delivered to the cancerous cells
Why is it good to use monoclonal antibodies to treat cancer?
The drug will only accumulate where there are cancer cells and so reducing damage to normal cells in the body, reducing the side effects
Other than to treat cancer what is another use for monoclonal antibodies?
They are used in pregnancy tests to detect very small amounts of the hormone HCG
Why are babies often immune to diseases which they haven’t had yet?
They have the antibodies from their mother for the first few months of their lives
Why are babies only protected with their mothers antibodies for the first few months of their lives?
They will have foreign antigens on their surface and so the babies immune system will start to destroy the antibodies
