Immunity Flashcards
What is the first line of defence in the immune response?
Physical and chemical barriers:
- Skin and mucous membranes
- HCl from stomach
What is the second line of defence in the immune response?
-Phagocytes
-Inflammation
This increases permeability of red blood cells in an area (swelling/pain etc.)
What happens in phagocytosis?
- Foreign antigen
- Phagocyte recognises with chemoattrctants
- Engulfs pathogen through Endocytosis
- Lysosomes fuse with vacuole and release lysozymes
- Lytic enzymes hydrolyse pathogens
- Macrophage becomes ‘antigen presenting’
- Helper T cell sees this and releases proteins to activate other cells
Where are helper T cells found?
T for thymus
How do the Helper T cells trigger a macrophage response?
By releasing lymphokines
What is the cell mediated response?
- Helper T cell releases interleukin
- Activates cytotoxic T cells
- produces memory cells that recognise antigens to provide a secondary immune response
- produces effector T cells that release perforins to kill cancer and virus cells
What are perforins?
Proteins that cause cells to burst, empties contents
What activates the humoral response?
Helper T cells release cytokines
What is the initial humoral response?
- B cell recognises antigen
- Antigen- receptor complex, which triggers Helper T cell activation of B cell replication
Replication of B cells
Plasma cells
- secrete antibodies
- each B cell only makes one type of antibody
Memory cells
- recognise past antigens to provide a secondary immune response
Where a B cells found?
Found in bone marrow
Why do common colds effect people even once they’ve had it?
This is due to antigen variability, due to gene mutations and natural selection, the antigen changes shape so that the body can no longer recognise it.
Why don’t we normally get the same infection twice?
Both B cells and cytotoxic T cells produce memory cells that will remember how to fight the antigen. When an antigen is recognised, the memory cells will be activated to produce plasma cells that can create specific antibodies.
How is HIV spread?
Through the exchange of body fluids
How does HIV cause disease?
- HIV GP120 receptor attaches to surface of Helper T cell (CD4 receptor)
- viral reverse transcriptase enzyme makes DNA copy of viral RNA
- Virus DNA is inserted into DNA of T cell, viral DNA stays inactive for a while
- Virus becomes ‘active’ and helper T cell makes new viruses
- New viruses released from cell, infecting and killing other helper T cells.
- Destruction of T cells result in AIDs
What are monoclonal antibodies?
identical copies of antibodies made in laboratories, and that come from one plasma cell. They have been isolated and cloned
How are monoclonal antibodies produced?
- Injecting particular antigens into an animal like mice
- Mice produce plasma cells with antibodies
- Tumour cells added to plasma cells to create hybridomas
What are hybridomas?
A fusion of tumour cells and plasma cells that can rapidly produce antibodies
What ethical issues surround the use of monoclonal antibodies?
- It requires giving cancer to mice
- You need to make animals transgenic
- Testing on humans has resulted in organ failure
- Some Multiple Sclerosis patients have died as a result
What is the use of monoclonal antibodies in pregnancy testing?
- Women produce hCG in urine when pregnant
- Home pregnancy tests contain monoclonal antibodies that form a coloured complex when hCG
- Makes a coloured line appear on a positive pregnancy test
What does hCG stand for?
Human chronic gonadatrophin
Describe the procedure of the ELISA test
- Apply blood sample to a slide where the antigens can attach
- Wash surface to remove unattached antibodies
- Add complementary monoclonal antibodies to attach to the antigens
- Wash again to remove excess antibodies
- Add second antibody complementary to first and has an enzyme attached.
- Add the colourless substrate of the enzyme, when hydrolysed produces a coloured substance
- Concentration of antigen is relative to colour intensity
What are the uses of the ELISA test?
- To detect HIV and pathogens of other diseases such as TB and hepatitis B
- Useful to measure quantities of antigens in blood
How are the products of phagocytosis removed?
Soluble debris is removed by exocytosis and harmless products are absorbed
