Immunology Flashcards
Describe the non-specific defence mechanisms the body may launch against pathogens. (5)
The process is called phagocytosis – no mark
- Pathogen is engulfed by the phagocyte.
- Engulfed pathogen enters the cytoplasm of the phagocyte in a vesicle.
- Lysosomes fuse with vesicle releasing digestive enzymes.
- Lysosome enzymes break down the pathogen.
- Waste materials are ejected from the cell by exocytosis.
Describe how a phagocyte destroys a pathogen present in the blood.
- Engulfs
- Forming vesicle/phagosome and fuses with lysosome
- Enzymes digest/hydrolyse
Give two types of cell, other than pathogens, that can stimulate an immune response.
- (Cells from) other organisms/transplants
- Abnormal/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.
- Vaccine contains antigen from pathogen
- Macrophage presents antigen on its surface
- T (helper) cell with complementary receptor protein binds to antigen
- T cell stimulates B cell
- With complementary antibody on its surface
- B cell divides to form clone producing same antibody
- B cell secretes large amounts of antibody
Explain how the humoral response leads to immunity.
- B cells specific to the antigen reproduce by mitosis.
- B cells produce plasma and memory cells.
- Second infection produces antibodies in larger quantities and quicker.
Describe and explain the role of antibodies in stimulating phagocytosis.
- Bind to antigen
- (Antibodies) cause clumping/agglutination OR attract phagocytes
Describe the difference between active and passive immunity.
- Active involves memory cells, passive does not
- Active involves production of antibody by plasma cells/memory cells
- Passive involves antibody introduced into body from outside/named source
- Active long term, because antibody produced in response to antigen
- Passive short term, because antibody (given) is broken down
- Active (can) take time to develop/work, passive fast acting
State why some antibodies are referred to as monoclonal.
(Antibodies) produced from the same B cell/plasma cell
Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why.
- Specific primary structure
- Specific tertiary/3D structure/shape;
- So only binds to/complementary to one antigen
Describe the structure of the human immunodeficiency virus (HIV).
- RNA (as genetic material)
- Reverse transcriptase
- (Protein) capsid
- (Phospho)lipid (viral) envelope OR Envelope made of membrane
- Attachment proteins
Describe how a person infected with HIV will develop AIDS (if untreated) and die of secondary infections.
- High viral load leads to increased destruction of helper T cells
- Less activation of B cells/cytotoxic T cells/phagocytes
- Less production of plasma cells/antibodies OR less able to kill virus infected cells (With cytotoxic T cells)
- More able to destroy other pathogens OR more able to destroy mutated/cancer cells
Describe the role of antibodies in producing a positive result in an ELISA test.
- First antibody binds/complementary (in shape) to antigen
- Second antibody with enzyme attached is added
- Second antibody attaches to antigen
- (Substrate/solution added) and colour changes
