Immunology 2.4 Flashcards
Describe how HIV is replicated (4)
- RNA converted into DNA using reverse transcriptase;
- DNA inserted into T Helper cell’s nucleus/Genome/DNA;
- DNA transcribed into HIV mRNA;
- HIV mRNA translated into new HIV viral proteins to be assembled into virions/viral particles (in host cell’s Golgi apparatus)
Give two types of cell, other than pathogens, that can stimulate an immune response (2)
- (Host) cells infected by virus;
- Transplanted cells (non-self);
OR abnormal/tumour/cancer cells
Describe how a phagocyte destroys a pathogen present in the blood (3)
Primary cell-mediated immune response:
- Engulfs a pathogen and forms a vesicle (phagosome);
- Vesicle fuses with lysosome;
- Enzymes digest vesicle (kill pathogen)
Describe how the Ebola virus stimulates a humoral immune response (3)
1.Antigen/Glycoprotein on Ebola binds to/stimulates a specific B cell;
2. These cells replicate by Mitosis;
3. Plasma/B cells release/produce specific (complementary) antibodies.
Name what is secreted by these cells involved in the immune response:
Cytotoxic T cells secrete ->
T Helper cells secrete ->
Plasma/B cells secrete ->
C -> Perforin
T -> Cytokines
P/B -> Specific (complementary) antibodies
State the function of Humoral immunity-B cells
- Each B cell has an antigen receptor (tertiary protein) molecule on the surface of their membrane
- with a complementary shape to a specific antigen
- Secrete antibodies into bodily fluids and cavities to kill microbes
State the structure and function of the variable region of an antibody (1)
Has a specific tertiary structure which can bind two antigens at the same time (Agglutination forming an antigen-antibody complex)
Explain how a scientist could use an ELISA test to determine the presence of an antigen
- Add antibody specific to antigen with enzyme attached to sample;
- Wash sample to remove unattached antibodies;
- Add substrate to cause a colour change (in positive test)
State the function of antibodies in agglutination (1)
Specific antibodies bind to the antigens on a pathogen and clump them together (forming an antigen-antibody complex)
State the function of antibodies in Oponisation (1)
Antibodies mark pathogens so phagocytes recognise and destroy the pathogen more efficiently.
State the function of antibodies in Lysis (1)
Complementary antibodies bind to antigens (Antigen-antibody complex) and lead to the destruction of the pathogens membrane.
Describe the non-specific défense mechanisms the body may launch against pathogens (5)
Phagocytosis (no mark)
1. Pathogen is engulfed by phagocyte;
2. Engulfed pathogen enters cytoplasm of phagocyte in vesicle (forming a phagosome);
3. Lysosomes fuse with vesicle releasing digestive enzymes;
4. Lysozymes break down/hydrolyse / digest pathogen;
5. Waste materials are ejected from cell by exocytosis.
Define endocytosis and give an example of this (1)
Cell engulfs (material) into vesicles
- Phagocytosis engulfs pathogens into vesicles
Describe how a phagocyte destroys a pathogen present in the blood (3)
- Engulfs;
- Forming vesicle/phagosome;
- Lysozymes/enzymes digest/hydrolyse pathogen.
Give two types of cell, other than pathogens, that can stimulate an immune response (3)
- Transplanted cells / foreign/non-self cells from other organisms;
- Cancer/tumour cells;
- Cells infected by virus.
When a vaccine is given to a person, it leads to the production of antibodies against a disease causing organism. Describe how (5)
- Vaccine contains antigen from pathogen;
- Macrophage (A-PC) presents antigen on surface;
- T helper cell with complementary receptor protein binds to antigen (cell-cell recognition);
- T cell stimulates B cell;
- (With) complementary antibody on surface;
- B cell divides (by mitosis) to produce clones of same antibody;
- B cell secretes large amounts of antibody.
Explain how the humoral response leads to (secondary) immunity
- B cells specific to the antigen reproduce by mitosis;
- B cells produce plasma and (B) memory cells;
- Second infection produces antibodies in larger quantities and quicker.
Describe and explain the role of antibodies in stimulating phagocytosis (2)
- Antibodies bind to antigen / OR are markers (opsonisation = marking)
- Antibodies cause agglutination/clumping (for phagocytes).
Describe the difference between active and passive immunity (5)
- Active involves (producing B) memory cells whereas passive does not;
- Active involves production of antibody by plasma/memory cells whereas passive does not;
- Passive involves antibody introduced into body from outside/named source;
- Active is long term as antibody produced in triggered (immune) response to antigen whereas passive is short term;
- Passive is fast-acting (+ large quantity) whereas active can take time to work.
State why some antibodies are referred to as monoclonal (1)
- Antibodies produced/cloned from a single clone of B cells / plasma cells;
OR from same B cell
Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why (3)
- Specific primary structure / order / sequence of amino acids;
- Specific tertiary / 3D structure;
- (So) only complementary to one antigen.
Describe the structure of the human immunodeficiency virus (HIV) (5)
- RNA (as genetic material);
- Reverse transcriptase;
- (Protein) capsomeres / capsid;
- Phospholipid (viral) envelope;
- Attachment proteins
(extrinsic)
Describe how a person infected with HIV will develop AIDS (if untreated) and die of secondary infections (4)
- High viral load leads to increased destruction of T helper / CD4 cells;
- Less activation of B cells / cytotoxic T cells / phagocytes;
- Less production of plasma cells/antibodies
(OR fewer cytotoxic T cells able to kill virus infected/host cells) - Less able to destroy other pathogens / microbes
(OR mutated/cancer cells)
Describe the role of antibodies in producing a positive result in an ELISA test (4)
- (First) antibody binds / is complementary (in shape) to antigen;
- (Second) antibody with enzyme attached is added;
- (Second) antibody attaches to antigen;
- Substrate/solution added so colour change (if +).
Suggest some ethical issues surrounding the use of monoclonal antibodies
• Production involves animals;
• Drug trials could cause organ failure (against arthritis and leukaemia)
