Immunology A1 Flashcards
Describe the non-specific defence mechanisms the body may launch against pathogens
(5 marks)
The process is called phagocytosis – No Mark
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;
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 secreting /
producing same antibody; - B cell secretes large amounts of antibody;
Describe the difference between active and
passive immunity. (6)
- 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 a single clone of B cells / plasma cells;
OR
(Antibodies) produced from the same B cell / plasma cell;
What is specific immunity and why is it effective?
A specific response to an antigen on the surface of a cell or pathogen that has been recognised as non-self.
Define antigen.
- an antigen is a molecule (usually protein)
- that stimulates an immune response resulting in the production of specific antibodies
- the body recognises the pathogen/antigen as ‘non-self’.
Why are viruses usually out of reach to antibiotics?
- they use host cells to carry out metabolic activities in so don’t have any reaction to disrupt.
- they have a protein coat rather than a murein cell wall which doesn’t allow antibiotics to work as they do with bacteria.
How does HIV replicate? (5)
- HIV attaches to receptor on lymphocyte
- HIV injects its genetic material into the lymphocyte, which becomes a host cell
- HIV uses the lymphocytes cellular machinery to make copies itself
- after making many copies of itself, the host cell is destroyed by HIV
- HIV infection eventually leads to decreased lymphocyte numbers and reduced ability to produce antibodies
What is a vaccine?
- certain protein/weakened microorganism
- stimulates production of antibodies + produce memory cells
How do antibiotics work?
- by preventing bacteria making normal cell wall (murein)
- so bacteria is unable to resist osmotic pressure and the cells burst
Define antibody.
- protein/glycoprotein made in response to foreign antigen
- has binding sites which specifically bind to antigen (only active sites in enzymes, everything else = binding site)
- produced by B cells
What is an antigen-antibody complex?
- specific antibody binds with specific antigen
- causing an antigen-antibody complex
When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism.
Describe how.
-cellular response (mark 1-3)
-humoral response (4-7)
- vaccine contains antigen from pathogen
- macrophage (antigen presenting cell) 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 (via mitosis)
- B cell secretes large amounts of antibody
What is clonal selection?
- a specific T cell binds to presented antigen via its complementary receptor
- T cell is activated and clones produce many T cells with complementary receptors to the antigen.
When a T cell is activated, it clones into two different types of T cell.
Name and describe the role of each T cell.
- cytotoxic T cell (killer t) - locate and destroy body cells (to stop infections spreading) that are already infected by the pathogens that caused the immune response.
- Helper T cell - releases chemicals (cytokines) that attract phagocytes and B cells to the area of infection. Activates B cells (you start feeling better).