Cell Recognition And Immune System Flashcards
What allows the immune system to identify things?
Each type of cell has specific molecules on its surface identify these molecules include proteins and enable the immune systems to identify things
What do the protein molecules enable the immune system to identify
Pathogens
Cells from other organisms of the same species
Abnormal body cells
Toxins
Describe non-specific defence mechanism
Response is immediate and the the same for all path
Describe specific defence mechanism
Respond to slower and specific to each pathogen
Examples of specific and non-specific defence mechanisms
Non-specific
-Physical barrier, e.g. the skin
-phagocytosis
Specific
-Cell mediated response, T lymphocytes
-humoural response, B lymphocytes
Define antigen
Proteins on surface of foreign cell
Toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies
What protein structure are antigens?
Quaternary structure as it has four polypeptide chains joined together
How do b cells respond to foreign antigens?
There’s a variety of B cells a different shapes of receptor
T helper cells activate the cells and simulate them to divide by mitosis
cells with the right shape of receptors for antigen is stimulated to divide
plasma cells secrete antibody
antibodies cause pathogens to clump together this is them harmless and prepare them for destruction
Describe the steps of phagocytosis
The phagocyte is attracted to the pathogens by chemoattractants moves towards a pathogen a longer concentration gradient. The phagocyte bind the pathogen.
Lysosomes within the phagocyte migrate towards the phagosome formed by engulfing the bacterium.
The lysosomes release the lyric enzymes where they break down the bacteria.
The breakdown products of the bacteria are absorbed by the phagocyte
Define endocytosis
The movement of large molecules into cells using vesicles eg phagocytosis
Define exocytosis
Movement of lodge molecules out of cells using vesicles the phago lysosomes fused with the cell membrane and release the debris from the broken down pathogen
How do you T cells respond to a foreign antigen?
A phagocyte has engulfed a pathogen and displays the antigen on its surface
The antigen is displayed to many different T cells in the lymph node
Clonal selection -stimulated t cell divide many times
Helper T cells – these secrete chemicals which simulate phagocyte cells stimulate the cells to produce antibodies and activate killer t cells
Killer T cells - these bind to cells presenting the complementary antigen
T memory cells formed after injection
Describe perforin
Causes perforation in the cell member and making the self full permanent
Describe b lymphocytes
Matures in bone marrow
Involved in humoral immunity
Produce antibodies
Responds to foreign material outside body cells
Responds to bacteria and viruses
Describe T lymphocytes
Matures in thyroid gland
involved in cell mediated immunity responsd to foreign material inside body cells
response to cells altered by viruses or cancer to transplanted tissue
What protein structure are antibodies?
Quaternary structure proteins (4 polypeptide chain)
What are antibodies secreted by?
B lymphocytes eg plasma cells in response to specific antigen
What do antibodies bind to ?
Bind specifically to antigens forming antigen antibody complexes
How do antibodies lead to the destruction of pathogens ?
Antibodies bind to antigens on pathogens forming an antigen antibody complex (specific tertiary structure so binding site /variable region binds to complementary antigen )
Attract phagocytes
Phagocytes bind to the antibodies and phagocytose many pathogens at once
What is a monoclonal antibody?
Antibody produced from genetically identical /cloned B lymphocytes/plasma cells
So have same tertiary structure
How can monoclonal antibodies be used in medical treatments?
Monoclonal antibody has a specific tertiary structure/binding site /variable region binds
Complementary to receptor /protein/antigen found only on a specific cell type(e.g cancel cell)
Therapeutic drug attached to antibody
Antibody binds to specific cell forming antigen antibody complex delivering drug
Some mAbs are also designed to block antigens/ receptors on cells
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How can mAbs be used in medical diagnosis?
(E.g pregnancy tests)
mAb has a specific tertiary structure /binding site/variable region
Complementary to specific reception /protein /antigen associated with diagnosis
Dye /stain/fluorescent marker attached to antibody Antibody binds
Antibody binds to receptor/protein/antigen forming antigen antibody complex
Explain the use of antibodies in the ELISA (enzyme-linked immunosorbent
assay) test to detect antigens
Attach sample with potential antigens to well
Add complementary monoclonal antibodies with enzymes attached → bind to antigens if present
Wash well → remove unbound antibodies (to prevent false positive)
Add substrate → enzymes create products that cause a colour change (positive result)
Explain the use of antibodies in the ELISA (enzyme-linked immunosorbent
assay) test to detect antigens
(Sandwich elisa)
Attach specific monoclonal antibodies to well
Add sample with potential antigens, then wash well
Add complementary monoclonal antibodies with enzymes attached → bind to antigens if present
Wash well → remove unbound antibodies (to prevent false positive)
Add substrate → enzymes create products that cause a colour change (positive result)
Explain the use of antibodies in the ELISA test to detect antibodies
Attach specific antigens to well
Add sample with potential antibodies, wash well
3. Add complementary monoclonal antibodies
with enzymes attached → bind to antibodies if
present
4. Wash well → remove unbound antibodies
5. Add substrate → enzymes create products that
cause a colour change (positive result
Suggest the purpose of a control well in the ELISA test
● Compare to test to show only enzyme causes colour change
● Compare to test to show all unbound antibodies have been washed away
Discuss some general ethical issues associated with the use of vaccines and
monoclonal antibodies
● Pre-clinical testing on / use of animals- potential stress / harm / mistreatment
○ But animals not killed & helps produce new drugs to reduce human suffering
● Clinical trials on humans- potential harm / side-effects
● Vaccines - may continue high risk activities and still develop / pass on pathogen
● Use of drug - potentially dangerous side effects
Explain the differences between the primary & secondary immune response
Primary- first exposure to antigen
○ Antibodies produced slowly & at a lower conc.
○ Takes time for specific B plasma cells to be
stimulated to produce specific antibodies
○ Memory cells produced
● Secondary- second exposure to antigen
○ Antibodies produced faster & at a higher conc.
○ B memory cells rapidly undergo mitosis to
produce many plasma cells which produce
specific antibodies
Explain the effect of antigen variability on disease and disease prevention
● Antigens on pathogens change shape / tertiary structure due to gene mutations (creating new strains)
● So no longer immune (from vaccine or prior infection)
○ B memory cell receptors cannot bind to / recognise changed antigen on secondary exposure
○ Specific antibodies not complementary / cannot bind to changed antigen
Define vaccine
Injection of antigens from attenuated (dead or weekend) pathogens simulating formation of memory cells
How do you vaccines provide protection to individuals against disease?
Specific be lymphocyte with complementary receptor binds to antigen specific T-helper cell binds to antigen-presenting cell and stimulates cell lymphocytes by mitosis to form clones some differentiate into B plasma cells which release antibodies some differentiate into B memory cells on secondary exposure to antigen be memory cells rapidly divided by mitosis to produce B plasma cellsThese release antibodies faster and that’s a higher concentration.
Explain how vaccines provide protection for populations against disease
Heard immunity – large proportion of population vaccinated reducing spread of pathogen large proportion of population amuse so they don’t become ill from the infection. Thus there’s fewer infected people to pass on the pathogen/unvaccinated people less likely to come in contact with someone with disease.
Describe active immunity
Initial exposure to antigen e.g. vaccine or primary infection memory cells involved antibody produced and secreted by B plasma cells slow takes longer to develop long-term immunity as antibody can be produced in response to specific antigen again
Describe passive immunity
No exposure to antigen
No memory cells involved
Antibody introduced from another organism for example, breastmilk/cross placenta from mother
Faster acting
Short term immunity as antibody hydrolysed
Describe the replication of HIV in helper T cells
HIV attachment proteins attached to receptors and help a tea cell lipid envelope, fuses of cell surface membrane releasing cap into cell capsule coach releasing RNA reverse transcript reverse transcript convert viral RNA to DNA viral DNA inserted into help a T cell DNA viral protein/captured or produced DNA transcribed into HIV mRNA HIV mRNA translated into new HIV proteins virus particles assembled the released themselves
Explain all HIV causes the symptoms of acquired immune deficiency syndrome AIDS
HIV facts and kills helper T cells (host cell) as it multiplies rapidly so so tea helper cells con stimulates toxic, B cells and Fargo sites
so be plasma cells can’t release as many antibodies for a glaciation and destruction of pathogen
immune system deteriorates more acceptable to opportunistic infection Pathogens reproduce, releasing toxins and damage cells
Explain why antibiotics are ineffective against viruses
Viruses do not have metabolic processes/ribosomes and viruses do not have bacterial enzymes/Mirin cell wall
