CELL RECOGNITION AND IMMUNE SYSTEM Flashcards
why aren’t self cells, but pathogens, abnormal body cells, toxins and cells from other organisms, recognised as foreign
as each type of cell has specific molecules on its surface that enable it to be identified
cells other than self cells will have molecules (often proteins) with a different tertiary structure to our own
What is an antigen (DEFINITION)
foreign proteins present on the cell surface membrane that stimulate an immune response
How can bacteria or pathogens survive in the body and what is this called
as a mutation occurs changing the tertiary structure of the antigens on its cell surface membrane
this may lead to the immune system not being able to detect the pathogen or bacteria and no immune response is triggered
ANTIGENIC VARIABILITY
What is phagocytosis and what is the process
BEBP
- Engulfment of a pathogen by a phagocyte
- Phagocyte is attracted to pathogen by chemical signals and will bind to it via receptors
- pathogen is engulfed by endocytosis to form a phagosome
- lysosomes will then fuse with the pathogen and lysozymes will break down the pathogen into soluble materials
- phagocyte will present pathogens antigens on its surface to become an antigen-presenting cell
What are the 2 types of lymphocytes and where are they matured
B cells ( bone marrow)
T cells ( thymus gland)
What is the cell mediated response and what is the process
- T cell receptors bind to foreign antigens which stimulates rapid division of t cells to produce clones
- these clones can differentiate into either T helper or T killer cells, or they can stimulate phagocytosis
What do T killer cells do
they produce perforin, a protein which makes holes in the cell membrane of pathogens, to allow substances to enter the pathogen causing cell death
What are antibodies and what response are they involved in
protein that has complementary binding sites to antigens and will lead to destruction of the pathogen
Humoral response
Describe the structure of an antibody
(3 comments)
Has a quaternary structure as has 4 polypeptide chains
Has 2 light chains and 2 heavy chains which are linked by disulphide bridges
Has a constant region and a variable region(this makes the antibody specific to a specific antigen)
What is the humoral response and describe the process
Helper T cells bind to the foreign antigen and will stimulate B cells to divide rapidly by mitosis to form clones of plasma cells (CLONAL SELECTION)
Plasma cells produce antibodies that have a specific shape that is complementary to the said antigen so they attach and cause destruction of the pathogen
How do antibodies destroy pathogens
AGGLUTINATION
Antibodies that have formed antibody-antigen complexes will stick together, which makes it easier for the pathogen to be digested by phagocytosis as the large clumps of antigens are more likely to be detected
Why is the secondary immune response much quicker than the primary
As memory B cells are formed after the primary response,
which will produce the antibodies specific to the antigens that were present in the primary response,
so when the pathogen enters the body again, it can produce antibodies much quicker and a much higher volume in order to destroy the pathogen quicker
How do vaccines work and what type of immunity is it ( and what immunity does it provide)
They contain a small amount of a dead or inactive pathogen
causing a primary immune response
leading to formation of B memory cells specific to the pathogen
upon re infection, a secondary response is stimulated, meaning antibodies are produced much faster
ARTIFICIAL ACTIVE IMMUNITY
PROVIDES HERD IMMUNITY
ethical issues with vaccines
Who are vaccinations tested on?
Should they be compulsory?
are they 100% effective in the long term?
What is active immunity
immunity that results from antibody production by own immune system in response to antigen presence
VACCINATION
What is passive immunity
Immunity that results from introduction of antibodies from another person or animal
ANTIVENOM (artificial) OR BREASTFEEDING(natural)
What is a monoclonal antibody and what is the main use of them
Type of antibody that’s isolated from a single clone of B cells
used for drug targeting, they are specific to the target of that drug
Ethical issue with monoclonal antibodies
Mice are used to produce them
Describe the ELISA test for certain antigens
IM WEWS
Used for detection of antigens
- monoclonal antibodies specific to antigen of interest immobilised at the bottom of the reaction vessel
-sample of patients blood plasma is added, and antigens will bind to antibodies if present
- apparatus is washed to remove unbound antigens
-secondary monoclonal antibodies are added, which are linked to colour changing enzymes and will bind to antigens if present
-apparatus is washed again to remove unbound antibodies
-complementary substrate to enzymes are added, if a colour change occurs it shows that they have bound to active site and therefore presence of antigen
Describe the structure of HIV
Attachment proteins which can bind to host cell receptors
Capsid which protects genetic material and reverse transcriptase enzymes
RNA as genetic material
Viral envelope
Describe HIV replication
Glycoproteins attach to CD4 receptors on T helper cells
RNA and enzymes are injected into host cell
Reverse transcriptase converts RNA into cDNA which can then enter T cell nucleus
cDNA from virus is transcribed and translated using host machinery to produce viral proteins that make new viruses
new virus particle break of T cell membrane to cause more replication
How does HIV cause aids
Helper T cells die when HIV particles break off membrane
Decreased B cell stimulation so decrease
humoral immunity
vulnerable to infections which can be fatal
How is HIV treated
Reverse transcriptase is targeted so that viral RNA cannot be converted to cDNA, preventing viral replication as virus proteins will not be produced by the host cell
Why are antibiotics ineffective against viruses
viruses and bacteria replicate in different ways and have different structures
