cell recognition and the immune system Flashcards
what is an antigen?
a foreign protein that stimulates an immune response
what types of cells do antigens enable the immune system to identify?(4)
pathogens
cells from other organisms of the same species
abnormal body cells
toxins.
what is antigenic variation and what effect does it have on disease prevention?
when mutations cause antigens to alter their tertiary structure
As a result, memory cells do not detect the altered antigens and are no longer effective against the pathogen.
what type of white blood cell is involved in non-specific response?
phagocyte
what are the 4 stages of phagocytosis?
phagocyte engulfs the pathogen forming a phagosome
lysosomes containing lysozymes fuse with the phagosome
the lysozymes hydrolyse the pathogen
the antigens are presented on the cell surface membrane.
what lymphocytes are involved in the cell mediated response and where do they mature?
T-lymphocytes mature in the thymus gland
how do helper T-cells begin a response to infection?
receptors on a specific helper T-cell binds to an APC
this activates the T-cell to begin dividing by clonal selection
what can cloned T-cells do?(4)
develop into memory cells
stimulate phagocytosis
stimulate B-cells to divide and secrete antibodies
activate cytotoxic t-cells
how do cytotoxic T-cells kill pathogens?
they produce a protein called perforin
perforin creates holes in the cell membrane, making it freely permeable and thus killing the cell
what lymphocytes are involved in the humoral response and where do they mature?
B-lymphocytes mature in the bone marrow
describe the humoral response(4)
helper T-cell with complementary receptor binds to antigen on an APC
stimulates a specific B cell with complementary antibody on its surface
this stimulates the b-cell to divide and produce many plasma cells that all produce the same antibody
or produce memory cells which will be able to recognise and more rapidly destroy the same pathogen in the future.
what are antibodies?
a protein that is produced by a plasma b-cell
describe the structure of an antibody(2)
have a quaternary structure with 2 heavy polypeptide chains and 2 light polypeptide chains joined by disulfide bridges
each antibody has 2 identical antigen binding sites that have a specific tertiary structure that is complementary to a specific antigen
what 2 ways can antibodies kill a pathogen?
agglutination
acting as a marker for phagocytes
how does agglutination help destroy pathogens?
each antibody can bind to 2 antigens and clump them together making it easier to engulf or deactivating viruses
how does acting as a marker help destroy pathogens?
antibody binds to the pathogens antigen and the constant region is then recognised by a phagocyte
what is a monoclonal antibody
Identical antibodies that have been produced by a single b-cell that has been cloned
what are the 5 steps of an (direct) ELISA test?
specific monoclonal antibody is attached to plate
sample is added, if there are antigens with a complementary shape they will bind to the antibodies
rinse plate to get rid of unbound antigens
add a second MAB that is attached to an enzyme, rinse again
add substrate for the enzyme
what is a vaccine?
introduction of dead or inactive pathogens with specific antigens to produce an immune response
how do vaccines protect against disease?
vaccine contains dead antigen
memory cells made on first encounter
on second exposure, memory cells recognise antigen and produce more antibodies more rapidly
antibodies destroy pathogens before they cause harm
what is passive immunity?(2)
introduction of antibodies from an outside source
it is short term because the antibodies will eventually be broken down
what is active immunity?(2)
when own immune system is stimulated to produce antibodies
it is long term because memory cells are produced
what is herd immunity?
when a sufficiently large proportion of the population has been vaccinated against a disease, making it difficult for the disease to spread.
name 5 structures of a HIV
lipid envelope
attachment proteins
reverse transcriptase
capsid
RNA
how does HIV lead to AIDS?
HIV attacks T-cells so immune system becomes weaker
this means less antibodies are produced as less b-cells are activated
how does HIV replicate?(6)
- attachment proteins on the HIV bind to CD4 receptors on a helper T-cell
- RNA and reverse transcriptase is inserted into the cell
3.Reverse transcriptase converts RNA to DNA - viral integrase inserts DNA into host cells DNA
5.viral mRNA is transcribed at ribosomes, forming viral proteins - Virus is assembles and released from the cell
what are 4 uses of monoclonal antibodies?
treating cancer
research
medical diagnosis
drug testing
how can MABs be used for treating cancer?
a radioactive cytotoxic drug can be attached to an antibody which will then deliver it to the cancer cells with the complementary antigens
what are some ethical issues to do with vaccines?
production often involves animals
may have side effects
some people may not want to have a vaccine
what are ethical issues of using MABs?
production involves mice
some risks of treatment failing
clinical tests may be risky
