2.4 Immunity Flashcards
name 4 things the body needs to defend itself from
- pathogens
- Non-self material such as cells from other organisms of same species
- toxins such as those produced by a certain pathogen
- abnormal body cells like cancerous cells
what does a phagocyte do
ingest and destroy the pathogen by phagocytosis
what does a lymphocyte do
evolves an immune response
what are the 6 steps of phagocytosis
- phagocyte recognises the foreign antigens
- pathogen is engulfed
- this is enclosed in a vesicle
- the vesicle fuses with the lysosomes
- the lysosome releases enzymes
- pathogen is digested
define antigen
a protein on the cell surface membrane of an organism that is recognised as foreign by the immune system
what are the 2 types of lymphocytes
B lymphocytes
T lymphocytes
define B lymphocytes
mature in the bone marrow
they are associated with humeral immunity
define T lymphocyte
mature in thymus gland
they are associated with cell mediated immunity
what are cells that display foreign antigens on their own cell-surface called
Antigen presenting cells (APCs)
5 steps of T lymphocytes response:
- pathogens invade body cells or are taken in by phagocytosis
- the phagocytes places antigens from the pathogen on its cell-surface membrane
- receptors on specific T helper cell are complementary to this specific antigen
- this attachment activates the T cell to divide rapidly by mitosis and form a clone of genetically identical cells
- the cloned T cells; develop into memory cells allowing for future fast responses, stimulates phagocytosis, stimulates B cells to divide and secrete antibodies and activates cytotoxic T cells
Define cytotoxic T cell
they kill abnormal cells by making holes in the cell surface membrane meaning it becomes freely permeable to all substances and it dies as a result
what are the 2 types of B cells
plasma cells and memory cells
what are plasma cells
secrete antibodies but only survive for a few days, these antibodies lead to the destruction of the antigen which is an immediate defence against infection
this is primary immune response
what are memory cells
these can live for decades, they don’t directly produce antibodies but they circulate in the blood. if they encounter the same antigen they will rapidly divide and develop into plasma and more memory cells.
this is secondary immune response
step of B cells
- the surface antigens of invading pathogens are take up by a B cell
- the B cell processes the antigens and displays them on its own cell surface
- Helper T cells attach to the processes antigens and activates the B cells
- the B cell now divides by mitosis to give a clone of plasma cells
- the cloned plasma cells produce a specific antibody that exactly fits the antigen on the pathogens surface
- the antibody destroys the antigens on the invading pathogen
- some B cells develop into memory cells for secondary immune response
what are antibodies made from
4 polypeptide chains where one pair is light (shorter) and the other is heavy (longer)
how do the antibodies lead to the destruction of antigens
- they cause agglutination of the cells where clubs of them are formed making it easier for the phagocytes to ingest them
- they then serve as markers that stimulate phagocytes to engulf the bacterial cells to which they are attached
how can monoclonal antibodies target specific cells
the antibodies are specific to the cancerous cells antigens, these antibodies attach to the caner cells only, they block the chemical signals that stimulate their uncontrolled growth
how are monoclonal antibodies used in pregnancy testing
pregnant women produce more hCG in their urine, these monoclonal antibodies are present on the test strip and if hCG is present then it will end to these antibodies and move along the strip until trapped by a different antibody creating a coloured line
ethical problems of MAbs
to produce them mice have to be given cancer
unknown risks
what is passive immunity
the introduction of antibodies into individuals from an outside source, so no memory cells produced so not long term
what is natural passive immunity
a baby getting antibodies through the placenta and in breast milk
what is artificial passive immunity
injected with antibodies such as anti-venom in snake bites
what is active immunity
stimulating the production of antibodies by the individuals own immune system, longer lasting and memory cells are produced
what is natural active immunity
individual becoming immune after getting infected with a disease as now have antibodies
what is artificial active immunity
vaccination injecting a harmless dose of the antigen
what is herd immunity
when a sufficiently large proportion of the population has been vaccinated the pathogen will have a hard time spreading between the population
ways that vaccination may not eliminate disease:
- vaccination fails to introduce immunity to certain individuals
- individuals may develop the disease immediately after the vaccination so immunity level not high enough
- pathogen may mutate changing its antigens
- some people may object the vaccine through medical or ethical reasons
ethical issues with vaccines
- production of vaccines often involve animals
- vaccines have side effects that can cause harm
8 steps of HIV replication
- HIV enters the bloodstream and circulates around the body
- Glycoprotein molecules on the virus’ surface bind to CD4 receptors on T helper cells
- this allows the virus envelope to fuse with the T helper cell membrane
- the capsid is released into the cell where is releases RNA and reverse transcriptase
- Reverse transcriptase is used to make DNA from the HIV RNA template
- The DNA is inserted into the cells DNA which gets replicated when the cells replicate
- DNA is used to make HIV RNA and proteins at host ribosomes
- Virus particles are assembles which bud off from the cell membrane and go on to infect other cells
how does HIV cause AIDS
HIV attacks T helper cells, without a sufficient amount to T helper cells the immune system cannot stimulate B cells to produce antibodies. As a result the immune system is weak
what is ELISA test for
To detect HIV
7 step of the ELISA test
- apply the sample to a surface ti which all the antigens are complementary
- Wash the surface several times to remove any unattached antigens
- add the antibody that is specific to the antigen we are trying to detect and leave the two to bind together
- wash the surface to remove excess antibody
- add a second antibody that binds with the first antibody which has an enzyme attached to it
- add the colourless substrate of the enzyme. the enzyme acts in the substrate to change into a coloured product
- the amount of the antigen present is relative tot he intensity of the colour test
why are antibiotics ineffective against a viral disease
one way antibiotics work is by preventing bacteria from making normal cell walls. so water enters the cell via osmosis and as there is no murrain o protect the cell then the cell bursts. However, viruses rely on host cell to carry out their metabolic activities therefore antibiotics are ineffective as there are no metabolic structures for them to disrupt
