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
