9. Immunology Flashcards
What is an antigen?
A foreign protein that stimulates production of antibodies.
What is phagocytosis pf pathogens?
Phagocytes recognise pathogen as foreign so engulf pathogen forming a vesicles called phagosome. This fuses with lysosome. Lysosome releases hydrolytic enzymes (lysozymes) which hydrolyse and destroy the pathogen.
Phagocytosis can result in antigen presenting cells.
What is an antibody?
A protein with a quaternary structure with 4 polypeptide chains (2 light and 2 heavy) , 2 variable binding sites and a constant region. Disulphide bridges join 2 polypeptides together.
They have a specific tertiary structure and different binding sites thats complementary and specific to one antigen so bind forming a antigen antibody complex.
What is the cellular response?
Cell presents its antigens on its cell surface. T cell binds to antigen by specific/complementary receptors. This activates T cells to divide by mitosis into many clones that differentiate into T helper cells. Helper T cells bind to antigen on antigen presenting cell stimulate release cytoxic T cells, release cytokine chemicals and B cells.
What do cytotoxic T cells do?
Bind to infected cell, perforin makes holes in infected cell membrane so cell lyses ,killing the infected cell.
What happens during humoral response.?
B cell binds to pathogen , Antigen presented by a phagocyte to a helper T cell. T cell binds to complementary receptors and activates B cells to divide by mitosis to produce many clones. Differentiate into plasma cells ( secrete specific antibodies to antigen) and B memory cells (remain in body to give rapid response.)
How is a plasma cells adapted?
Many mitochondria to produce atp for protein synthesis.
Extensive Golgi to make vesicles to secrete antibodies.
What is antigenic variability?
When present different antigens on surface so no longer specific and complementary to antibody so primary response has to be carried out again.
How does the formation of antigen antibody complexes lead to destruction of antigens?
Agglutination- antibodies bind to antigen antigen acting as marker for phagocytosis causing clumping of pathogens attracting phagocytes to engulf and hydrolyse bacterial cells.
Whats primary immune response?
When antigen 1st enters the body.
Process slow as takes time for correct B cells to be activated, divide and differentiate into lots plasma cells to produce antibodies with complementary shape.
Experience symptoms as T and B cells mount an immune response and both produce memory cells.
Whats the secondary immune response?
When antigen enters body again.
T and B memory cells mount recognise antigen and start dividing. B memory cells divide into plasma cells to produce many antibodies which are complementary to antigen on pathogen.
No symptoms as much quicker so pathogen is suppressed before experience symptoms.
How do vaccines work and why are they given multiple times?
Vaccine contains antigen from pathogen, antigen presented on its surfce, specific T helper cell binds to antigen by complementary receptors and activates B cells using cytokines. B cell divide by mitosis forming clones that differentiate into plasma cells ( produce large number antibodies thats specific to antigen ) ad some memory cells ( that produce plasma cells and antibodies on future infections).
Multiple times to produce more memory cells so higher conc antibodies in blood so produced quicker upon future infections.
Whats the difference between active and passive immunity?
Active- involves production of antibodies + memory cells by patients own immune system .e.g. vaccine or enter body naturally. -involves plasma cells and antibody production, long term as antibody produced in response to antigen, can take long time to develop.
Passive- introduction of antibodies from another source .e.g. breast milk. -no memory cells produced, no plasma cells/antibodies produced, short term as antibody given is destroyed, fast acting.
What does a fall in the number of vaccines do?
Decreases herd immunity so increase likelihood diseased people meet non vaccined people.
What does anti venom do?
Anti venom injected into person. Anti venom contains antibodies against snake toxin which bind to toxin and target it for destruction. This example of passive immunity, active would be too slow.
How does HIV replicate?
Virus Attachment proteins bind to specific and complementary receptors on T helper cell. Virus injects RNA in to host cell. Reverse transcriptase converts RNA to DNA. Host cell golgi and ribosomes produce viral proteins which assemble and released from cell.
Why does HIV cause symptoms of AIDs?
Decrease number T helper cells as destroyed, less antibodies produced so fewer B cells activated and undergo mitosis and differentiate into plasma cells.
Whats the ELISA test to detect antigens?
Attach selected monoclonal antibody to well and rinse away unbound.
Add sample and if antigen present will produce antigen antibody complex.
Add 2nd antibody with enzyme attached, which will bind to antigen if present.
Substrate added.
Enzyme catalyses reaction cause colour change and confirms presence of antigen.
Whats the ELISA test to detect antibodies?
Antigen attached to test well.
Sample added and if antibody present they will bind to antigen.
Well washed.
2nd antibody with enzyme attached added which will bind to antibody being detected.
Well washed again to remove unbound antibodies
Solution added containing substrate for enzyme, solution change colour if enzyme present showing antibodies is present.
What are monoclonal antibodies and the ethical issues?
They are antibodies with the same tertiary structure produced from cloned plasma cells. They can target medicine to specific cells based on cells antigen/receptors. They have a specific binding site.
Treatment may cause death, use animals for production may harm animals, human trials (not all side effects known)
Why are antibodies ineffective against viruses?
Viruses use host machinary to replicate as they are acellular.
Also only have a capsid so cant destroy by osmotic lysis.
Some viruses have no DNA to replicate so it cant be destroyed by inhibiting DNA replication.
