Section 2 - Cell recognition and the immune system Flashcards
How can tumour cells be destroyed in the immune system?
It is a foreign antigen
T-Cells will bind to faulty foreign protein
T-Cells will stimulate clonal selection of B cells
Release of antibodies against faulty protein
What is an antigen?
Cell-surface molecule which stimulates an immune response
What 4 things do protein molecules allows the immune system to identify?
Pathogens
Abnormal body cells
Non-self material
Toxins
What are the 2 types of white blood cell?
Phagocytes
Lymphocytes
What are phagocytes?
Ingest and destroy the pathogen by phagocytosis before it causes harm
What are the 2 types of lymphocyte?
B lymphocytes: associated with humoral immunity
(antibodies)
T lymphocytes: associated with cell-mediated immunity
(body cells)
What is the process of phagocytosis?
- Phagocyte engulf pathogens with any foreign antigen
- Lysosomes fuse with the phagosome releasing the lysosome onto the pathogen
- The lysozyme hydrolyses the pathogen
- Some of the antigens from the pathogen are represented on the surface of the phagocyte.
It becomes an antigen presenting cell.
What are the 3 types of T cells associated with the cell-mediated response?
Helper T cells - activate phagocytes, B cells, Tc cells
Cytotoxic T cells- destroys infected body cells
Memory T cells- provide long term immunity
What are 2 differences between a specific and non-specific defence mechanism?
Specific mechanism: distinguishes between different pathogens but responds more slowly
Non-specific: treats all pathogens, responds more rapidly
Why does it take the body’s immune system a couple of days to control a pathogen after it gains entry?
Lymphocytes need to build up their number
What is the process of the cell-mediated response?
- Receptors on a specific helper T cell bind to an antigen presenting cell
- Attachment activates T cell to divide by mitosis forming clone of genetically identical cells
- Clones T cells develop into memory cells, stimulate phagocytes, stimulate B cells and activate Tc cells
How do cytotoxic T cells kill infected cells?
Protein is produced called perforin
Makes holes in cell-surface membrane
membrane becomes freely permeable to all substances and dies
What are 2 similarities between T cells and B cells?
Both are types of white blood cell
Have a role in immunity
Produced from stem cells
What are 2 differences between T cells and B cells?
T cells mature in thymus gland
B cells mature in bone marrow
T cells involved in cell-mediated immunity
B cells involved in humoral immunity
What is the humoral response controlled by?
B-lymphocytes
What is the role of plasma cells?
To secrete antibodies
What are memory cells responsible for?
The secondary immune response
What is the process of the humoral response?
- Surface antigens are taken up by a B cell and placed on B-cell surface
- Helper T cells attach to antigens activating B cell which divide by mitosis to give a clone of plasma cells
- Cloned plasma cells produce specific antibody
- Antibody attaches to antigen on the pathogen and destroys them
- Some B cells develop into memory cells
What 3 organelles would you expect to find in large quantities in plasma cells that produce 2000 protein antibodies each second?
Rough endoplasmic reticulum- to make and transport proteins
Golgi apparatus- to sort and process proteins
Mitochondria- to release the energy needed for such antibody production
What are antibodies?
Proteins with specific binding sites synthesised by B cells.
What is the structure of an anitbody?
4 polypeptide chains (2x heavy, 2x light)
Binding site: binds to complementary antigen
Disulphide bridge: holds antibody together
Constant region: attaches to phagocyte
Hinge region: movement, improves efficiency
How do antibodies lead to the destruction of a pathogen?
Formation of antigen-antibody complex results in agglutination which enhances phagocytosis
What are monoclonal antibodies?
Antibodies produced from a single clone of B cells.
What are memory cells?
Specialised T helper cells produced from primary immune response
Can divide very rapidly by mitosis if organism encounters the same pathogen
What is the difference between the primary and secondary immune response?
SECONDARY RESPONSE:
Faster rate of antibody production
Shorter time lag between exposure and antibody
Higher concentration of antibodies
Pathogen usually destroyed before any symptoms
Why are antibodies made of proteins, rather than carbohydrates, are more likely to be effective against a wide range of diseases?
Only proteins have the diversity of molecular structure to produce millions of different types.
How does antigen variability affect the incidence of disease?
Memory cells no longer complementary to antigen - individual can catch disease again
Many varieties of a pathogen - difficult to develop vaccine
What is passive immunity?
Produced by the introduction of antibodies into individuals from an outside source.
Antibodies not replaced - no memory cells
(Antivenom)
What is active immunity?
Stimulating production of antibodies by individuals own immune system.
What are the 2 types of active immunity?
Natural active = body produces own antibodies after infection
Artificial active = inducing immune response without suffering symptoms of disease
What are the 2 types of active immunity?
Natural active = body produces own antibodies after having infection
Artificial active = inducing immune response without suffering symptoms of disease
(immunisation)
What is herd immunity?
When significant number of population are immune.
What are features of a successful vaccination programme?
Economically available in sufficient quantities
Few side effects
Means of producing, storing, transporting vaccine
Means of administering vaccine properly at effective time
Possible to reach herd immunity
What is attenuation?
Weakening pathogen in a vaccine
Why might a vaccine not eliminate a disease?
Vaccination fails to induce immunity in certain individuals
Pathogen may mutate
Too many varieties or pathogen
Individuals may object to vaccine
What are the differences between active and passive immunity?
Active: stimulated by own antibodies, long-lasting immunity.
Passive: antibodies introduced from outside rather than being produced by individual, short-lived immunity
Why is vaccinating against influenza not always effective?
Influenza virus displays antigen variability
Antigens change frequently and so antibodies don’t recognise virus.
What are some of the ethical issues surrounding the use of vaccines?
Production may involve use of animals
Potentially dangerous side-effects
Clinical tests may be fatal
What is the structure of the human immunodeficiency virus (HIV)?
Lipid envelope Attachment proteins Capsid RNA genome X2 Reverse transcriptase & integrase
What are some of the ethical issues surrounding the use of vaccines?
Production may involve use of animals
Potentially dangerous side-effects
Clinical tests may be fatal
How does HIV result in the symptoms of AIDS?
- Attachment proteins bind to complementary receptor on Th cells
- HIV particles replicate inside Th cells, killing or damaging them
- AIDS develops when there are too few Th cells for the immune system to function
- Individuals cannot destroy other pathogens and suffer from secondary diseases
How does the HIV replicate?
- HIV binds to protein CD4
- Protein capsid fuses with the cell-surface membrane. RNA and enzymes of HIV enter the helper T cell
- HIV reverse transcriptase converts RNA into DNA
- DNA is moved into helper T cell nucleus where it is inserted into cell DNA
- mRNA is created, containing instructions for making new protein
- mRNA passes out and makes more HIV particles
Why are antibiotics ineffective against viruses?
Antibiotics work by damaging murein cell walls to cause osmotic lysis.
Viruses have no cell wall.
Why is HIV called a retrovirus?
It possesses RNA and the enzyme reverse transcriptase which can make DNA from RNA
A reaction that is reverse of that carried out by transcriptase
What is the function of the Reverse Transcriptase in the HIV virus?
Makes DNA using genome
What are 4 aseptic techniques?
- Wipe surface with antibacterial cleaner
- Use Bunsen burner = draws microbes away
- Flame wire hoop
- Flame neck of bottle prevent bacteria entering
- Keep vessels open for minimum amount of time
- Close windows and doors to limit air currents
Why is bacteria incubated at 25 degrees?
To prevent growth of pathogens which occurs at higher temperatures
How can you compare effectiveness of different antibiotics applied to same bacteria?
Measure diameter and calculate area of zone of inhibition
What does zone of inhibition indicate?
Indicates bacteria killed by antibiotic
Larger zone = more effect antibiotic
What is the aseptic technique method?
- Wash hand and sterilise workspace
- Light Bunsen burner next to workspace
- Heat inoculating loop in flame until glowing red
- Allow inoculating time to cool before using (5-10 seconds)
- Flame neck bottle when opening it
- Open petri dish like ‘clam-shell’ keeping opening as small as possible
- Secure petri dish with 3 bits of tap to secure dish without preventing oxygen getting in
What is the method for using aseptic technique to investigate the effect of antimicrobial substances on microbial growth?
- Carry out aseptic technique.
- Use a sterile pipette or wire hoop to transfer bacteria from broth to agar plate
- Spread bacteria evenly over plate using a sterile plastic spreader.
- Use sterile forceps to place a multi disc antibiotic ring on the plate.
- Tape of lid with 3 pieces.
Why should the lid not be completely taped to petri dish?
Allows oxygen to enter petri dish, prevents growth of harmful anaerobic bacteria
What is the role of cytotoxic T cells in destroying the pathogen?
Makes holes in the cell-surface membrane
Cell becomes free permeable and dies
What are the structural features of a HIV virus?
RNA Reverse transcriptase Matrix Lipid envelope Capsid Attachment proteins
Why would blood clots form when antibodies attach to phospholipid molecules in cells?
Antibodies will agglutinate blood cells
Antibodies have 2 binding sites
What are 3 reasons why a hospital might use a multidisc to select the most suitable antibiotic for treating a patient?
Cheap
Quick to do
Compares antibiotic under same conditions
What is an antibody?
Protein produced by B cells
Explain why the part of the antibody molecule incorporating the binding site is often called the variable region?
Different antibodies have different amino acid sequences
Only complementary to a specific antigen
