Immunology Flashcards
(19 cards)
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
- hydrolytic enzymes;
- Lysosome enzymes hydrolyse /break down / destroy the pathogen.
- Waste materials are ejected from the cell by exocytosis;
What is an ANTIGEN? [2]
- Foreign protein;
Accept glycoprotein / glycolipid / polysaccharide - (that) stimulates an immune response / production of (specific) antibody;
Describe how a phagocyte destroys a pathogen present in the blood. [3]
- Engulfs pathogen;
- Forming vesicle/phagosome and fuses with lysosome;
- Hydrolytic enzymes hydrolyse / destroy pathogen
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
Explain how the humoral response leads to immunity. [3]
- 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. (Rapid & Extensive)
What is the role of the disulfide bridge in forming the quaternary structure of an antibody?
- Joins two (different) polypeptides;
Describe and explain the role of antibodies in stimulating phagocytosis. [2]
- Bind to antigen OR Are markers (Opsinisation);
- (Antibodies) cause agglutination (clumping) OR Attract phagocytes;
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;
- Phagocyte (other APC) 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 secreting / producing same antibody;
- B cell secretes large amounts of antibody (by exocytosis);
Describe the difference between active and passive immunity. [4]
- Active involves memory cells, passive does not;
- Active involves production of antibody by plasma cells/memory cells whereas, Passive involves antibody introduced into body from outside/named source;
- Active long term, because antibody produced in response to antigen whereas, Passive short term, because antibody (given) is broken down;
- Active (can) take time to develop/work, passive fast acting;
Describe the structure of the human immunodeficiency virus (HIV). [5]
- RNA (as genetic material);
- Reverse transcriptase;
- (Protein) capsomeres/capsid;
- (Phospho) lipid (viral) envelope OR Envelope made of membrane;
- Attachment proteins;
Name two features of HIV particles that are not found in bacteria. Do not include attachment protein in your answer.
- Capsid;
- Reverse transcriptase;
- RNA genome;
- Lipid Envelope;
State two ways pathogens cause disease.
- Destroy/Damage cells / tissues / organs
- Release toxins
What is a pathogen?
A microorganism that may cause disease/damage to the host, such as bacteria, virus, fungus, protist or parasite.
State 4 roles of a T helper cell.
Specific T Helper cell binds to the antigen presenting cell and….
1) Release cytokines that attract phagocytes to the area of infection.
2) Release cytokines that activate Cytotoxic Killer T cell (TC).
3) Activates a specifically complementary B cell.
4) Form memory TH cells
State three roles of a Cytotoxic Killer T Cell (Tc cell)
- Locate and destroys infected body cells that present the correct antigen.
- Binds to antigen-presenting-cells
- Releases perforin (protein) which creates holes in the cell surface membrane which destroys the APC.
How many binding sites are there on an antibody.
THREE
2x Antigen binding sites
1x Receptor binding site
Describe the stucture of an antibody. [5]
- A quaternary structured protein
- 2 Light polypeptide chains and 2 Heavy polypeptide chains
- Joined together by disulfide bridges
- 2 antigen binding sites within the variable regions
- 1 receptor binding site within the constant region
Describe the role of antibodies in producing a positive result in an ELISA test. (4 marks)
1. (First) antibody binds/attaches /complementary (in shape) to antigen;
2. (Second) antibody with enzyme attached is added;
3. (Second) antibody attaches to antigen;
Accept (second) antibody attaches to (first) antibody (indirect ELISA test).
4. (Substrate/solution added) and colour changes;
An ELIZA test can only detect the prescence of HIG antibodies. Give 2 reasons why it cannot be used to find out if a person has AIDS.
(To diagnose AIDS, need to look for / at)
1. (AIDS-related) symptoms;
2. Number of helper T cells.
