immunology Flashcards
.State two ways that pathogens cause harm/disease?
1- can produce toxins which can directly damage tissues
2- can sometimes replicate inside and destroy host cells
What is an antigen?
A molecule (usually a protein) that stimulates an immune response that results in the production of a specific antibody. (Antibody generator)
Common antigens: Glycoproteins & Glycolipids
Give the types of cell, other than pathogens, that can stimulate an immune response.
1- (Cells from) other organisms/transplants;
2- Abnormal/cancer/tumour (cells);
3- (Cells) infected by virus;
4- Pathogen (Bacterium / Fungus / Protist)
REJECT VIRUS (Acellular)
Describe the non-specific defence mechanisms the body may launch against pathogens (5 marks)
This is called PHAGOCYTOSIS
1-Pathogen is engulfed by the phagocyte.
2- Engulfed pathogen enters the cytoplasm of
the phagocyte in a vesicle;
3- Lysosomes fuse with vesicle releasing
digestive enzymes;
4- Lysosome enzymes break down the pathogen.
5- Waste materials are ejected from the cell by exocytosis;
Describe how a phagocyte destroys a pathogen present in the blood. [3]
1- Engulfs;
2- Forming vesicle/phagosome and fuses with lysosome;
3- Hydrolytic enzymes digest/hydrolyse;
When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how [6]
1- Vaccine contains antigen from pathogen;
2- Macrophage presents antigen on its surface;
3- T (helper) cell with complementary receptor protein binds to antigen;
4- T cell stimulates B cell;
5- (With) complementary antibody on its surface;
6- B cell divides to form clone secreting / producing same antibody;
7- B cell / Plasma cell rapidly secretes large numbers of antibody;
Describe the role of T-helper cells
1- binds to the antigen presenting cell
2- releases cytokines that attract phagocytes to the area of infection
3- release cytokines that activate Cytotoxic Killer T Cells(Tc)
4- activates a specifically complementary B cell
5- form memory T-H cells
What does the word ‘ethical’ mean?
Harm inflicted.
Describe the role of Tc Cell ( cytotoxic killer t cells)
1- locate and destroys infected body cells that present the correct antigen
2- binds to antigen-presenting-cells
3- releases Perforin( protein) which creates holes in the cell surface membrane which destroys the APC
Give three roles of cytokines
1- stimulate more phagocytic cells
2- stimulate clonal expansion
3- cause B cells to make and secrete antibodies
What is clonal selection/ expansion
1- A specific Th cell binds to presented antigen via its complementary receptor
2- T cell is activated and clones to produce many Th cells with complementary receptors to the antigen.
Explain how the humoral response leads to immunity. [3]
1- B cells specific to the antigen reproduce by mitosis.
2- B cells produce plasma and memory cells
3- Second infection produces antibodies in larger quantities AND more rapidly.
Explain the B cell activation
1- a specific Th cell with the correct receptor binds to the presented antigen and then locates AND ACTIVATES a specifically complementary B cell
2- the specific Th releases cytokine chemicals that signal the specific B cell to clone by mitosis(clonal expansion)
Which two types of cell does the B cell differentiate into ?
1- PLASMA CELLS
produce and secrete vast quantities of specific antibodies into the blood plasma
2- MEMORY(B) CELLS
remain in the body to respond to pathogen rapidly and extensively
What is an antibody
protein made in response to foreign antigen
Describe and explain the role of antibodies in stimulating phagocytosis.
-OPSINISATION: Bind to antigen OR Are markers;
AGGLUTINATION: (Antibodies) cause clumping/ aglutination OR attract phagocytes
How do antibodies assist in the destruction of pathogens?
1- agglutination
2- opsonisation
3- lysis : bind to antigens and destruct pathogen’s membrane
4- antitoxin and anti venom
5- prevent pathogen replication
Describe the difference between active and passive immunity. [5]
1- Active involves memory cells, passive does not;
2- Active involves production of antibody by plasma cells/memory cells;
3- Passive involves antibody introduced into body from outside/named source;
4- Active long term, because antibody produced in response to antigen;
5- Passive short term, because antibody (given) is broken down;
6- Active (can) take time to develop/work, passive fast acting;
State why some antibodies are referred to as monoclonal
(Antibodies) produced from a single clone of B cells / plasma cells;
OR
(Antibodies) produced from the same B cell / plasma cell;
Give some uses of monoclonal antibodies
1- research
2- immuno assays eg. pregnancy kits and ELISA
3- diagnosis ( showing presence of a particular antigen )
4- targeting drugs
5- killing specific cells
6- isolating specific chemicals
Different antibodies from the same organism bind to different antigens. Explain why
1- Variable region of each polypeptide has a different tertiary structure.
2- Variable region provides (highly) specific antigen binding site with specific shape.
3- Antigen binding site is only complementary to a specific antigen to form antigen antibody complex
What is the role of the disulfide bridge in forming the quaternary structure of an antibody?
Joins two (different) polypeptides
What are the ethical considerations associated with vaccines and monoclonal antibodies?
Animal & Human testing for production, efficacy and safety.
Animal rights.
Risk : Benefit ratio (if few people have severe side effects but the majority of the population have mild or no symptoms, is this justifiable?)
Vaccine availability: Free for all or who pays for those who can’t afford the preventative treatment.
Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why. [3]
1- Specific) primary structure / order of amino acids;
2- (Specific) tertiary / 3D structure / shape;
3- (So) Only binds to / fits / complementary to one antigen;
Describe the structure of the human immunodeficiency virus (HIV). [5]
1- RNA (as genetic material);
2- Reverse transcriptase;
3- (Protein) capsomeres/capsid;
4- (Phospho)lipid (viral) envelope OR Envelope made of membrane;
5- Attachment proteins;
Explain how HIV affects the production of antibodies when AIDS develops in a person. [3]
1- Less/no antibody produced;
2- (Because HIV) destroys helper T cells; Accept ‘reduces number’ for ‘destroys’
3- (So) few/no B cells activated / stimulated OR (So) few/no B cells undergo mitosis/differentiate/form plasma cells;
Describe how the human immunodeficiency virus (HIV) is replicated once inside helper T cells (TH cells). [4]
1- RNA converted into DNA using reverse transcriptase;
2- DNA incorporated/inserted into (helper T cell) DNA/chromosome/genome/nucleus;
3- DNA transcribed into (HIV m)RNA;
4- (HIV mRNA) translated into (new) HIV/viral proteins (for assembly into viral particles);
Name two features of HIV particles that are not found in bacteria. Do not include attachment protein in your answer. [2]
1- Capsid;
2- Reverse transcriptase;
3- RNA genome;
4- (viral lipid) Envelope;
Describe how a person infected with HIV will develop AIDS (if untreated) and die of secondary infections. [4]
1- High viral load leads to increased destruction of helper T/CD4 cells;
2- Less activation of B cells/cytotoxic T cells/phagocytes;
3- Less production of plasma cells/antibodies OR (With cytotoxic T cells) less able to kill virus infected cells;
4- (Less able to) destroy other microbes/pathogens OR (Less able to) destroy mutated/cancer cells;
What are ELISA tests used to determine
the presence of the antibody (indirect ELISA) or the antigen ( sandwich ELISA)
Describe the role of antibodies in producing a positive result in an ELISA test. [4]
1- (First) antibody binds/attaches /complementary (in shape) to antigen;
2- (Second) antibody with enzyme attached is added;
3- (Second) antibody attaches to antigen;
4- (Substrate/solution added) and colour changes;
Which immune cell destroys (self) cells infected with a virus?
Tc Cell
(Cytotoxic Killer T cell)
Which immune cell destroys bacteria?
Phagocyte
(e.g., Macrophage)
Name a virus that infects bacteria
Bacteriophage
When is a person / cell / organism infected by a virus such as HIV?
The moment the viral DNA is inserted into the host cells genome.
What is Herd immunity?
Only applicable to contagious pathogens.
When the majority of a population is vaccinated / immune to a contagious pathogen;
Those not yet vaccinated (Infants / eldery / immuno-suprressed/deficient) will have protection as the pathogen will spread less rapidly.
Herd Immunity Threshold is (usually) between 85-95% depending on the named pathogen.
Herd immunity applies a selection pressure to the named pathogen.
What threatens Herd immunity?
- Low vaccine uptake
- Vaccine hesitancy / choice not to vaccinate
- Mutation of pathogen
- Vaccine does not produce long term immunity
- Vaccinated population does not mix randomly
