Specific immune responses Flashcards
T lymphocytes (cells)?
- mature in thymus
- cell-mediated response - involves T cells & body cells
- ‘cell-mediated’ as T cells only respond to antigens that r presented on cells (APC) - not antigens detached
Antigen Presenting Cells (APC)
any cell that present a non-self antigen on surface e.g.
- infected body cells (present viral antigens)
- macrophage/phagocyte (present antigens)
- cells of a transplanted organ (diff shaped antigens)
- cancer cells (abnormal self-cell antigens)
* these trigger cell-mediated response
Cell-mediated response?
- once pathogen has been engulfed & destroyed by phagocyte - antigens positioned on cell surface aka APC
2. Helper T cells hv receptors on surface - attach on antigens on APC
3. Once attached ts activates helper T cells to divide by mitosis to replicate & make large nums of clones
4. Cloned helper T cells differentiate into diff cells:
- Cloned helper T cells differentiate into diff cells…
- helper Ts - activate B cells
- some stimulate phagocytes to perform more phagocytosis
- some become memory cells for that shaped antigen
- some become cytotoxic T cells aka killer T cells
Cytotoxic T cells?
- destroy abnormal/infected cells
- release protein - perforin - embeds in cell surface membrane - makes pore/hole so - any substance can enter or leave cell
- causes cell death/shrivel/lyse
- most common in viral infections as - viruses infect body cells
- body cells sacrificed to prevent viral replication
- why sore throat when cold - as cytotoxic T cells r destroying infected cells in throat
B lymphocytes (cells)?
- all lymphocytes made in bone marrow
- B cells mature there too
- humoral response: Involves B cells & antibodies
- antibodies r soluble & transport in bodily fluids (aka humour)
B cell activation?
*approx 10 mil diff B cells which hv antibodies on surface complementary to 10 mil diff antigens
- antigens in blood collide w complementary antibody on B cell - B cell takes in antigen by endocytosis & presents it on membrane
- when B cell collides w helper T cell receptor - activates B cell - clonal expansion (division) & differentiation (aka clonal selection)…
- B cells undergo mitosis to make large no. Cells - these differentiate into plasma or memory B cells
Plasma and memory B cells?
- plasma - make antibodies
- Memory - divide rapidly into plasma cells when reinfected with same pathogen - to make large no. antibodies rapidly
Memory B cells?
- can live for decades in body (plasma short lived)
- divide by mitosis & make plasma cells rapidly if collide w antigen they’ve previously encountered
- results in large no. Antibodies produced so rapidly that - pathogen destroyed b4 any symptoms can occur
- active immunity
Primary and Secondary immune response?
Pri - first exposure to the antigen/pathogen
- aren’t able to produce many antibodies quickly
- - production of antibodies & memory cells takes a while - the right immune cells to find the pathogen
Sec - 2nd exposure to same antigen - if memory cell collides w complementary antigen - differentiate into more memory cells & lots of plasma very rapidly so-
- lots of antibodies very quickly
- The memory cells are activated and rapidly divide into plasma cells which can then more rapidly produce more antibodies
Antibodies structure?
- quaternary protein structure - 4 polypeptide chains (2 short on outside, 2 on inside)
- variable region - change shape - complementary shape to specific antigen
- constant region - alw be the same
- heavy chain - longer ones in middle
- light chain
- antigen binding site - top bit
Agglutination?
- antibodies bind to antigen: Antigen-antibody complex
- antibodies r flexible so - can bind to multiple antigens to clump tgt
- makes easier for phagocytes to locate & destroy/engulf more efficieny
Vaccination?
involves injection of antigens that have been isolated from a dead/attenuated microorganism
- ts induces a primary immune response in an individual (production of memory cells) w/o them suffering symptoms of the disease
Passive immunity?
- introducing/inserting (monoclonal) antibodies into organism from an outside source
- pathogen/antigens don’t enter body so - plasma & memory cells not made
- no long-term immunity
- e.g. antibodies passed to a fetus thru placenta/thru breast milk to baby
Active immunity?
- involves direct contact w pathogen/antigens - stimulating body’s immune system to produce its own antibodies
1. Natural active: following infection and creation of body’s own antibodies & memory cells
2. Artificial active: following introduction weakened version of pathogen/antigens via vaccine
Examples of active & passive immunity - natural and artificial?
ACTIVE:
- natural: infection
- artificial: vaccination
PASSIVE:
- natural: maternal antibodies
- artificial: monoclonal antibodies
3 Differences between active & passive immunity?
active: antibodies secreted by plasma cells
passive: antibodies introduced into body from outside
active: longer term cos memory cells created
passive: short term cos no memory cells created & antibodies eventually break down
active: takes longer to develop
passive: fast acting
How do vaccines works?
- introducing antigens stimulates a primary immune response
- vaccine contains antigen - displayed on APCs
- soecific helper T cell activates B cell
- B cell - clonal expansion & differentiation (clonal selection)
- B cells undergo mitosis - large nums of cells - these differentiate into plasma/memory B cells
- plasma - make antibodies
- memory cells divide rapidly into plasma cells when re-infected w same pathogen - make large nums of antibodies rapidly
Herd immunity?
When a sufficiently large proportion of the population has been vaccinated to make it difficult for a pathogen to spread even to those not immunised
Ethical concerns of using vaccines?
- use of animals
- side effects
- who should be tested on?
- should trials only occur in specific countries?
- should it be compulsory?
- economical concerns
- greater food v individual health risks
When do vaccines not work?
- pathogen DNA can mutate frequently - if mutation occurs in gene which codes for antigen - shape of antigen will change
- ineffective as - antibodies can no longer recognise (not complementary to) antigens aka antigenic variability/memory cells hv mem of old antigen shape
Features of successful vaccination?
- financially available
- few side-effects - if any!
- ways of producing, storing and transporting the vaccine
- ways of giving (administering) the vaccine properly - may involve training staff
- be available in sufficient quantities to vaccinate most of the population - herd immunity
General - viruses?
- replicate inside cells - - difficult to destroy them w/o harming harming host cells
- hv diff mechanisms (e.g. respiration/protein synthesis) & no cell wall pores - diff to bacteria
- antibiotics interrupt/attack organelles of bacteria/reactions so - antibiotics ineffective against viruses
HIV structure?
- core: genetic material (RNA) & enzyme - reverse transcriptase - r both needed for viral replication
- capside - outer protein coat
- envelope - extra outer layer - made out of membrane taken from host’s cell membrane
- protein attachments - on exterior of envelope - enables virus to attach to host’s helper T cell
HIV general?
- infects person’s blood thru sex, sharing needles, blood transfusion
- can’t reproduce itself - host cell needed - T helper cells
- instructs host cell to produce components of new HIV viruses
Replication of HIV in helper T cells?
- HIV enters the bloodstream, it circulates around the body
- Virus binds (using attachment proteins) to receptor proteins (CD4) on the surface of a t-helper cells
- virus lipid envelope fuses with the cell surface membrane
- capsid breaks down and this releases the genetic material & enzymes into the cell
- Reverse transcriptase converts RNA to DNA
- viral DNA moves into the nucleus through a nuclear pore and is inserted into the host cell DNA by integrase
- HIV DNA is transcribed into mRNA & then translated into viral proteins
- These new viral particles are assembled and bud off from the cell surface membrane to infect more cells
- This destroys T helper cells
Retrovirus meaning?
- a group of viruses where virus is able to insert its genetic material into host cell’s DNA using enzyme: reverse transcriptase
AIDS?
- AIDS - when replicating viruses in helper T cells interfere w normal functioning of immune system
- a set of symptoms results from low T helper cells nums due to - rapidly replicating HIV
- w helper T cells destroyed - host unable to produce adequate immune response to other pathogens so - left vulnerable to infections & cancer
