2: The immune response Flashcards
Forms of responsive cells
Describe phagocytosis in 5 main stages
1: antigen’s chemical signal detected and followed by phagocyte
2: cytoplasm of phagocyte engulfs pathogen forming a phagocytic vacuole
3: a lysosome fuses and releases lysozymes which break down the pathogen
4:the pathogen disposed of waste then presents the pathogens antigens forming an APC.
Where do T cells mature?
The Thymus gland
How do T cells recognise a specific antigen?
T lymphocytes have many T cell receptors on their cell surface and there are so many unique T cells that every antigen is accounted for. The complementary receptor binds to its antigen.
What 4 cell types will T lymphocytes bind to?
1- infected cells( viral infection)
2- cancer cells
3- non self cells (transplanted)
4- APCs from phagocytosis
All have non self antigens presented on their cell surface for the T-cell receptors to bind to.
After T-cell receptors are activated by binding to their specific antigen, what occurs?
Activated T-cells undergo mitosis dividing into T-helper cells, Cytotoxic T-cells and T-memory cells.
What are the 3 main things that T-helper cells do?
1:Activate B cells to produce the plasma cells with the correct antibody
2:Release chemical signals to activate and stimulate phagocytes
3:Stimulate cytotoxic T-cells to kill abnormal body cells
What do Cytotoxic T-cells do?
Identify and bind to abnormal cells such as cancer cells or virally infected cells. They attach and release performing which makes holes in their cell surface membrane, destroying them.
What do T-memory cells do?
T- memory cells live for a long time within tissue fluid. Upon repeat infection, they rapidly differentiate into cytotoxic T-cells and at-helper cell. These kill damaging cells and stimulate B- cells for antibody production.
Describe the cell mediated response in 4 main steps:
1: a specific T- helper cell receptor is activated by an APC antigen, causing it to rapidly clone itself, making lots of T- helper cells for one specific antigen.
2: these cells then differentiate into memory, cytotoxic and (more) T- helper cells which do their jobs.
Why is the T-cell response cell mediated?
The immune response only reacts to antigens on cells, not free floating pathogens.
Describe the role of B lymphocytes in the humoral response.
B cells are white blood cells covered in antibodies. When they meet a complementary shaped antigen they bind to it. This along with the helper T-cell selection is clonal selection. The activated B cells divide into plasma cells which secrete lots of monoclonal antibodies.
Describe the structure of an antibody
4 polypeptide chains, two long two short.
Disulphide bridges
Variable/control regions
Hinge section
How do antibodies aid the destruction of pathogens?
Agglutination: antibodies bind two pathogens at once, allowing phagocytes to engulf them more efficiently.
Define active immunity and how it can be natural or artificial.
When the immune system makes its own antibodies
Natural: immunity from catching a disease
Artificial: vaccination
Describe passive immunity and how it can be natural or artificial
Immunity from being given antibodies made by another organism
Natural: antibodies from placenta or mothers milk
Artificial: injected with antibodies
What are 4 differences between active and passive immunity?
Active requires exposure to antigen whereas passive doesn’t.
Active takes time for protection to develop whereas passive is immediate.
Active produces memory cells whereas passive doesn’t.
Active is long term wheres passive is short-term.
