immunity Flashcards
cell mediated response
- pathogen with foreign antigen detected
- phagocytosis and antigen presentation
- helper T-cell with complementary receptors bind
- activates specific T-cell to divide by mitosis
- T cells release cytokines
forms:
- specialise into cytotoxic T-cells
- stimulate phagocytosis
- stimulate B cells
- stimulate plasma cells
- increase rate of phagocytosis
humeral response
- pathogen with foreign antigens detected
- phagocytosis and antigen presentation
- helper T-cell receptors bind to antigen (complementary)
- helper T-cells stimulate specific B-cells
- clonal selection - divides by mitosis
forms:
- plasma cells
secrete antibodies which clump pathogens, easier to engulfs and inactive
phagocytosis
- phagocyte recognises foreign antigen
- phagocyte engulfs pathogen
- forms phagosome
- lysosomes fuse with phagosome
- creates phagolysosome
- lysozymes hydrolyse pathogen
- antigen presentation
activates immune response
what is an antigen?
cell surface molecule on cell membrane
triggers an immune response
used to identify as self or foreign
complementary to antibodies
antibodies
secreted by plasma cells
2 sites bind to antigens on pathogen
forms antigen - antibody complex
agglutination - clumps pathogens together, engulfed
proteins - chains of amino acids
variable regions = antibody binding sites - different tertiary structure, specific
complementary to a specific antigen
same constant regions
Heavy and light chains
describe the primary response
when antigen enters body for the first time and activates immune response
- slow - not many specific plasma cells to make antibodies
- shows symptoms
- eventually produces enough antibodies to overcome
T and B cells produce memory cells
- remain in blood for long time
- T cells remember specific antigen
- B cells remember specific antibodies
now immune - can respond quickly
describe primary response on graph
concentration stays low for several days aren’t many b cells to produce complementary antibody
Antibody concentration increases as specific b cells divide to make plasma cells, which make many antibodies
Increases to peak until plasma cells die
Doesn’t return to pre exposure levels as memory cells remain in body
describe the secondary response
same pathogen enters the body again
quicker and stronger
clonal selection happens faster
- memory B cells activated and divide to plasma cells, make specific antibody
- memory T cells activated into specific t cell to kill antigen
often kills pathogen before symptoms (immune)
differences between primary and secondary
secondary =
- more antibodies made, faster
- shorter lag time
- no symptoms (pathogen killed before)
- antibodies concentration remains high for longer
how do vaccines work?
contain antigens to disease
on dead or altered pathogen
injected or taken orally (may be broken down by enzymes)
antigen causes body to produce memory cells against specific pathogen
immune without getting symptoms
protect people who had them - reduce occurrence
protect all - herd immunity, less likely to get it as less people to catch it from
what is antigenic variation?
changes in genes of pathogen cause a change in shape of anitgens
when infected again, memory cells from primary response don’t recognise antigens
primary response needed again
- takes time and shows symptoms
makes it hard to develop vaccines
- memory cells it produces don’t recognise new antigens
memory cells from one strain won’t recognise antigens of different strains - immunologically different
active immunity
when own immune systems makes its own antibodies
when stimulated by antigen
natural - immune after catching disease
artificial - immune after vaccination
- requires exposure
- takes time
- memory cells produced
- long term - antibody produces themselves
passive immunity
when given antibodies made by a different organism - own system doesn’t make any
natural - baby immune due to antibodies from mother, placenta and milk
artificial - immune after injected with antibodies made by someone else
- doesn’t require exposure
- immediate protection
- no memory cells
- short term - antibodies broken down
HIV structure
capsid - outer coating of protein
containing genetic material (RNA) and proteins (reverse transcriptase)
envelope - made from membrane of host cell
attachment proteins on envelope - allow it to accept to receptors
HIV replication
- attachment protein on HIV attaches to receptors on helper T cell (host)
- injects genetic material and enzymes into cell, releases genetic material into cytoplasm
- reverse transcriptase used to make complementary strains of DNA from viral RNA template
- makes double stranded DNA that is inserted into host cells DNA
- host cell enzymes used to make viral proteins fro viral DNA
- viral proteins assembled into viruses, bud from cell, using membrane
how does HIV cause AIDS?
infects and kills helper T cells
- used to activate phagocytosis, cytotoxic T cells and B cells
without enough, immune system unable to respond efficiently
AIDS when numbers drop below certain level
makes them more vulnerable to other infections
initial symptoms - minor infections
as it progresses - number of immune cells decreases more, susceptible to more serious infections eg TB
late stages have very low numbers
killed by serious infections not HIV
why do antibiotics not work on viruses?
kill bacteria by interfering with metabolic reactions
- target bacterial enzymes and ribosomes
viruses use human host cells enzymes and ribosomes
- antibiotics don’t target human ones
antivirus drugs designed to target virus specific enzymes
eg reverse transcriptase inhibitors
monoclonal antibodies (+ uses)
antibodies produced from a single group of genetically identical b cells
(all have same tertiary structure)
- cancer treatment
- pregnancy tests
use of monoclonal antibodies to treat cancer (targeting specific cells)
cancer cells have different antigens to normal body cells
- tumour markers
monoclonal antibodies can be made that are complementary to tumour markers
- anticancer drugs can be attached
means they will bind
- only accumulate where the cancer cells are
- more specific, less side effects
use of monoclonal antibodies in pregnancy tests (medical diagnosis)
detect hCG in pregnant women’s urine
monoclonal antibodies made complementary to hCG
- application area has antibodies complemenray to hCG bound to coloured bead
- when urine applied, any hCG will bind forming antigen-antibody complexes
- urine moves up test strip carrying any beads with it
- test strip has antibodies complementary to hCG stuck in place
- if hCG present, test strip goes coloured
immobilised antibody binds to hCG with coloured bead - concentrates on strip
(none present, passes over)
outline the ELISA test
can see if a patient has antibodies to a certain antigen or antigens to a certain antibody
used to test for pathogenic infections, allergies etc
uses antibody with an enzyme attached, reacts with substrate to make a colour change
colour change = antibody/antigen present
quantity = intensity of colour
indirect ELISA test (testing for antibodies)
- antigen bound to bottom of a well in a well plate
- sample of patients blood added
- any antibodies complementary to the antigen will bind - plate washed to remove unbound antibodies
- secondary antibody added
- has specific enzyme - secondary antibody binds to any primary antibody on bottom of well
- washed again
- solution added
- contains a substrate which reacts with enzyme attached to secondary
produces a coloured product making solution change colour
- they have the antibodies
direct ELISA tests (testing for an antigen)
Detect specific antigen
- patents sample added to well
- specific antibody complementary to antigen tested for added
- antibody added has enzyme attached
- washed and substrate added
- if enzyme present (so antigen present) = colour change
uses one antibody - complementary to antigen being tested for
(indirect uses 2)
ethical issues with monoclonal antibodies and vaccines
monoclonal antibodies:
animals used in testing and production of the antibodies
- unethical
vaccines:
often tested on animals
can create side effects
who recieves vaccines first
why do specific blood types need to be used in transfusions?
a transfusion with incorrect cell with have antigen recognised as foreign
this will trigger an immune response and the cells will be destroyed
why are vaccinations not always effective?
antigen variation
not everyone gets vaccinated
