2c cells and the immune system Flashcards
1
Q
what do foreign antigens trigger
A
an immune response
2
Q
what are antigens
A
molecules that can generate an immune response when detected.
3
Q
where are antigens usually found
A
on the surface of cells
4
Q
what are antigens used to identify
A
pathogens, abnormal body cells, toxins and cells from other individuals of the same species.
5
Q
what are the 4 main stages in the immune response
A
- phagocytes enfulf pathogens
- phagocytes activates t-cells
- t-cells activate B-cells, which divide into plasma cells
- plasma cells make more antibodies to a specific antigens.
6
Q
phagocyte
A
a type of white blood cell that carries phagocytosis
7
Q
where are phagocytes found
A
in the blood and in tissues and are the first cells to respond to an immune system trigger inside the body
8
Q
how do phagocytes work
A
- a phagocyte recognises the foreign antigens on a pathogen
- the cytoplasm of the phagocyte moves round the pathogen, engulfs.
- the pathogen is now contained in a phagocytic vacuole in the cytoplasm of the phagocyte
- a lysosome fuses with the phagocytic vacuole. the lysozymes break down the pathogen.
- the phagocyte then presents the pathogen’s antigens - it sticks on its surface to activate other immune system cells.
9
Q
t cell
A
a type of white blood cell. it has receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes. activating the t-cell.
10
Q
how do different types of t cells respond
A
in different ways
11
Q
helper t-cells
A
release chemical signals that activate and stimulate phagocytes
12
Q
cytotoxic t-cells
A
kill abnormal and foreign cells
13
Q
T h cells
A
Activate b-cells which secrete antibodies
14
Q
what do t cells activate
A
b-cells which divide into plasma cells
15
Q
b cells
A
a typle of white blood cell covered with antibodies
16
Q
antibody
A
protein that bind antigens to form an antigen-antibody complex
17
Q
why do different b cells bind to different shaped antigens
A
because they have different shaped antibodies
18
Q
how do b cells divide into plasma cells
A
- when the antibody on the surface of a b-cell meets a complementary shaped antigen, it bind to it
- this together with substances released from helper t cells activates the b- cell. this process is called clonal selection
- the activated b-cells divides into plasma cells
19
Q
what do plasma cells do
A
make more antibodies to a specific antigen
20
Q
what are plasma cells identical to
A
the b-cells (theyre clones)
21
Q
what else do plasma cells do
A
they secrete loads of antibodies specific to the antigen. these are called monoclonal antibodies
22
Q
what do monoclonal antibodies do
A
they bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes
23
Q
what does an antibody have
A
two binding sites, so can bind to pathogens at the same time.
24
Q
agglutination
A
when the pathogens clump together
25
what destroys pathoges
phagocytes bind to the antibodies and phagocytose many pathogens at one. this process leads to the destruction of pathogen carrying this antigen in the body
26
what are antibodies
proteins made up of chains of amino acids. its specialty depends on its variable region
27
how can the immune response be split
cellular, humoral
28
cellular immune response
the t-cells and other immune system cells that they interact with
29
humoral immune response
b-cells clonal selection and the production of monoclonal antibodies
30
why are both types of immune response neede
to remove a pathogen from the body and the responses interact with eachother
31
primary immune response
1. when an antigen enters the body for the first time it activates the immune system
2. the primary response is slow because there arent many b-cells that can make the antibody needed to bind to it
3. eventually the body will produce enough of the right antibody to overcome the infection. meanwhile the infected person will show symptoms of the disease
4. after being exposed to an antigen both t-cells and b-cells produce memory cells, which remain in the body for a long time. memory t-cells remember the specific antigen and will recognise it the second time round. memory b cells record the specific antibodies needed to bind the antigen
5. the person is now immune - their immune system now has the ability to respond quickly to a second infection
32
secondary immune respons e
1. if the same pathogen enters the body again, the immune system will produce a quicker, stronger immune response
2. clonal selection happens faster. memory b-cells are activated and divide into plasma cells that produce the right antibody to the antigen. memory t-cells are activated and divide into the correct type of t-cells to kill the cell carrying the antigen
3. often gets rid of the pathogen before you begin to show any symptoms
33
what can vaccines do
protect individuals and populations against disease
34
what can vaccination help avoid
you suffering from a disease while your b-cells are busy dividing to build up their numbers to deal with the pathogen
35
what do vaccines contain
antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease. this means you can become immune without getting any symptoms
36
how can vaccines protect individuals and cause herd immunity
they reduce the occurrence of the disease therefore those not vaccinates are also les likely to catch the disease
because there are fewer people to catch it from
37
how can antigens in a vaccine be
free, or attached to a dead or weakened pathogen
38
how and vaccines given
injected, or taken orally
39
disadvantages of taking a vaccine orally
could be broken down by enzymes in the gut or the molecules may be to large too be absorbed into the blood
40
why are booster vaccines sometimes given
to make sure memory cells are produced
41
what does antigen variated cause
helps some pathogens evade the immune system
42
what do antigens on the surface of pathogen activate
the primary response
43
what happens when your infected the second time with a pathogen
they activate the secondary response ad you dont get ill
44
what can some pathogens do
change their surface antigens
45
antigen variation
different antigens can be formed due to changes in the genes of a pathogen
46
what does antigen varaiation mean for the secondary response
the memory cells produced from the first infection will not recognise the different antigen. so the immune system has to start from scratch and carry out a primary response against these new pathogens
47
why do you get ill with the primary response
it takes time to get rid of the infection
48
what does antigen variation make difficult
developing vaccines against some pathogens
49
how does antigenic variation affect the population of vaccines to help prevent people catching influenza
1. influenza vaccine changes every year, because the antigens on the surface of the influenza virus changes regularly, forming new strains of the virus
2. memory cells produced from vaccination with one strain of the flu will not recognise other strains with different antigens. the strains are immunologically distinct
3. every year there are different strains so a different vaccine has to be made
4. new vaccines are developed and one is chosen every year that is most effective against the recently circulating influenza virus
5. governments and heath authorities then implement a programme of vaccination using the most suitable vaccine
50
active immunity
the type of immunity you get when your immune system makes its own antibodies after being stimulated by the antigen.
51
natural active
this is when you become immune after catching a disease
52
artificial active
this is when you become immune after youve been given a vaccination containing a harmless dose of the antigen
53
passive immunity
this is the type of immunity you get from being given antibodies made by a different organism - your immune system doesn't produce any antibodies of its own. again, there are two types.
54
natural passive
this is when a baby becomes immune due to the antibodies it receives from its mother, through the placenta and in breast milk
55
artificial passive
this is when you become immune after being injected with antibodies from someone else
56
active immunity characteristics
- requires exposure to antigen
- takes awhile for protection to develop
- memory cells are produced
- protection is long term because the antibody is produced in response to complementary antigen being present in the body
57
passive immunity characteristics
- doesnt require exposure to antigen
- protection is immediate
- memory cells arent produced
- protection is short term because the antibodies given are broken down
58
how can monoclonal antibodies be used
to target specific subtances or cells
59
what are monoclonal antibodies
antibodies produced from a single group of genetically identical b-cells. meaning they are all identical in structure
60
why are antibodies very specific
their binding sites have a unique tertiary structure that only one particular antigen will fit into
61
how to antibodies be used to target drug delivery to cancer cells
1. different cells have different surface antigens
2. cancer cells have antigens called tumour markers that are not found on normal cells
3. monoclonal antibodies can be made that will bind to the tumour markers
4. you can also attach anti-cancer drugs to the antibodies
5. when the antibodies come into contact with the cancer cells they will bind to the tumour markers
6. this means the drug will only accumulate in the body where there are cancer cells
7. so the side effects of an antibody based drug are lower then other drugs as they accumulate near specific cells
62
how can antibodies be used in pregnancy test
1. the application area contains antibodies for hCG bound to a coloured bead
2. when urine is applied to the application area any hCG will bind to the antibody on the beads, forming an antigen antibody complex
3. the urine moves up the tick to the test strip, carrying any beads with it.
4. the test strip contains antibodies to hCG that are stuck in place
5. if there is any hCG present the test strip turns blue because the immobilised antibody binds to any hCG, concentrating the hCG antibody complex with the blue beads. if no hCG is present, the beads will pass through the test area without binding to anything so it wont go blue.
63
what is the ELISA test
a medical diagnostic test
- allows you to see if a patient has antibodies to a certain antigen or any antigen to a certain antibody
64
why is important scientists find more evidence
to prove the validity of the theory by reproducing the results or conduct other studies to try and produce the same theory
65
what are vaccines tested on before humans
animals
66
what is the ethical issue with animal testing for vaccines
some people disagree. and animal based substances may be used to produce a vaccine which some people disagree with
67
why is testing vaccines on humans tricky
volunteers may put themselves at unnecessary risk of contracting the disease because the think they're fully protectedw
68
why do some people not take vaccines
due to the risk of side effects
69
what protects non vaccinated people
herd immunity
70
what would happen if there was a epidemic of a new disease
there would be a rush to receive a vaccine and difficult decisions would have to be made about who would be first to receive it
71
what do ethical issues surrounding monoclonal antibody therapy often include
animal rights issues as animals are used to produce the cells from which the monoclonal antibodies are produced
72
what is HIV
a virus that affects the immune system and eventually leads to aids
73
what is aids
a condition where the immune system deteriorated and eventually fails. this makes someone with aids more vulnerable to other infections, like pneumonia
74
how does HIV work
infects (and eventually kills) helper T-cells which act as host cells. withiout enough helper t-cells, the immune system is unable to mount an effective response to infections becasue other immune system cells dont behave how they should
75
what do helper T-cells do
they send chemical signals that activate phagocytes, cytotoxic cells and b-cells so theyre hugely important cells in the immune response
76
When does HIV turn into AIDS
when the helpter t-cell numbers in their body reach a critically low level
76
what is the core of HIV
contains the genetic material and some proteins (including the enzyme reverse transcriptase which is needed for virus replication)
77
what is the capsid of HIV
an outer coating of protein
78
what is the envelope of HIV
An extra outer layer made from a membrane stolen from the cells membrane of a previous host cell
79
what sticks out from the envelope on hiv
loads of copies of an attachment protein that help HIV attach to the host helper t-cell
79
how does HIV replicate
can only reproduce inside the cells of the organism it has infected as it doesnt have the resources to replicate on its own
79
process of HIV replication
1. the attachment protein attaches to a receptor molecule on the cell membrane of the host helper T-cell
2.the capsid is released into the cell where it uncoats and releases the genetic material into the cells cytoplasm
3. inside the cell, revers transcriptase is used to make a complementary strand of DNA from the viral RNA template
4. from this double stranded DNA is made ad inserted into the human DNA
5. host cell enzymes are used to make viral proteins from the DNA found within the human DNA
6. viral proteins are assembled into new viruses which bud from the cell and go on to infect other cells
80
what is the length of time between infection with HIV and the development of aids
varies between individuals but without treatment it is usually around 10 years
80
initial symptoms of aids
include minor infections of mucous membrane and recurring respiratory infection s
81
what happens as aids progresses
the number of immune system cells decreases further and patients become susceptible to more serious infections including chronic diarrhoea, severe bacterial infections and tuberculosis
82
what happens during the late stages of aids
patients have a very low number of immune system cells and can develop a range of serious infections such as toxoplasmosis of the brain and candidiasis of the respiratory system.
83
what factors effect the survival time of aids
- existing infections
- the strain of HIV they are infected with
- age
-access to healthcare
84
what do antibiotics do
kill bacteria by interfering with their metabolic reactions. they target the bacterial enzymes and ribosomes used in these reactions
85
what are antibiotics designed to target
bacterial enzymes and ribosomes so they dont damage human cells
86
why cant antibiotics inhibit viruses
because they use human enzymes and ribosomes to replicate, antibiotics cant inhibit them as they dont target human processes
87
what are reverse-transcriptase inhibitorrs
antiviral drugs designed to target reverse transcriptase and inhibit without affecting the host cell
88
is there currently a cure for HIV
No there is neither a cure or a vaccine but antiviral drugs can be used to slow down the progression of HIV infection and AIDS in an infected person
89
what is the best way to control HIV in a population
reducing its spread.
can be spread via unprotected sexual intercourse, infected bodily fluids and from a hiv positive mother to her fetus but not all babies from positve mothers are born infected
