9 - Disease and Immunity Flashcards
How do pathogens cause diease?
Damaging host cells
Releasing toxins
What is an antigen?
A non-self protein that stimulates an immune response of antibodies
Where are antigens found?
Can be on the surface of a cell or freely circulating in the blood (e.g. toxins)
Describe the non-specific immune response
Phagocytosis - a phagocyte recognises and binds to antigen
Phagocyte engulfs pahtogen
Pathogen enclosed in vesicle
Lysosome fuse with vesicle
Lysosomes contain hydrolytic enzymes that damage bacterial cell walls
These diges the pathogen by hydrolysis
What is an antigen presenting cell?
A phagocyte that places antigens from the pathogen onto it’s cell surface membrane
Give examples of antigen presenting cells
Cells that are infected by a virus
Phagocyte that engulfed and hydrolysed a pahtogen
An abnormal cell e.g. cancerous cell
Describe the cellular response
Antigen detected by receptor on specific T cell
Activates T cell to undergo mitosis to produce cytotoxic cells and memory cells and releases chemicals that active cytotoxic T cells, B cells and phagocytes
Cytotoxic T cells release perforins (proteins)
Describe the secondary immune response
When same antigen encountered at later date memory cels:
Divide rapidly
Produce large numbers of memory and plasma cells, therefore more antibodies produced faster
What is the function of plasma cells?
Produce and secrete antibodies
What do B cells divide into?
Plasma cells and memory cells
What does the humoral response involve?
B cells
What does the cellular response invole?
T cells
What do antibodies do?
React with antigens to form antigen-antibody complexes as theya re complementary shapes so antibodies are very specific
Why does vaccination not eliminate a disease?
Defective immune system so vaccination fails to induce immunity
Pathogen may mutate and change antigen shape (antigenic variation)
What are monoclonal antibodies?
Antibodies produced by B cells
All have the same tertiary structure and bind to one specific antigen
What happens during the ELISA test?
Add specific monoclonal antibodies to a solution suspected of containing a certain antigen
Antibodies will bind to the antigen if present
Enzyme attached to second antibodies, if present at the end the substance changes colour
Why is it important to wash after the second antibody is added? (ELISA)
To remove unbound 2nd antibody to prevent a false positive result
What would happen if there were no antigens present in the sample?
Antibodies would not have bound and would be washed away
No enzyme present to hydrolyse substrate so no colour change
How can the ELISA test detect the amount of antigen presesnt in a sample?
More antigens present, more antigen - antibody complexes formed so more enzyme substrate complexes so more coloured products
How do viruses (e.g. HIV) replicate?
Enter blood stream
Attachment proteins bind to specific, complementary receptors on T cells
Capsid injected into cell
RNA and enzyme released into cell
Complimentary strand of DNA made using RNA as template
What does the capsid in a virus contain?
RNA and enzyme (reverse transcriptase)
What are the symptoms of AIDS?
Infection of the lungs, intestines, brain and eyes
Fever and tiredeness
Weight loss
Diarrhoea
Why can’t antibiotics be used to treat viral infections?
Viruses do not posses structures targetted by drugs (e.e. cell walls or ribosomes)
Viruses have a different metabolism
Viruses infect body cells, so antibiotics cannot affect them without damaging the cell
