antigens Flashcards
unit 4
what is the simple structure of antigens?
Antigens are protein-based and are composed of one or more polypeptide chains. They can also be composed of carbohydrates, lipids, and nucleic acids.
What are antigens?
Antigens are unique protein-based molecules that are found on the surface of bacteria/virus cells (non-self cells) that the immune system recognises and takes action against. Antigens help the immunity of organisms.
Where are antigens recognised?
Antigens are recognised by the antibodies secreted or bound to B lymphocytes (b-cells)
They can also be recognised by the receptors on T lymphocytes (t-cells)
Where are antigens found and expressed?
Antigens are found in bacteria/virus cells and are expressed on the surface of the plasma membrane acting as a recognition site for the immune system. However this isn’t always the case as some antigens (such as toxins) are released by bacteria and circulate freely in body fluids.
What are allergens?
Allergens are antigens that result in hypersensetive reactions.
Hypersensetive/allergic reactions are over exaggerated and aggressive immune responses to harmless antigens
Examples of allergenic substances…
- pollen
- fur
- peanuts
- latex
- house dust
How does a hypersensetive reaction range?
A hypersensetive reaction ranges from mild to being life-threatening also known as anaphylaxis depending on the individual and their antigens.
Why are toxins harder to be reconised and acted apon in comparison to antigens expressed on the plasma membrane of cells?
Toxins are harder to be recognised because they are small and freely circulating in body fluids, making them harder to access in comparison to antigens on the plasma membrane of cells that also consist of recognition sites.
What is the relation between antigens and B lymphocytes?
B lymphocytes produce antibodies in two forms:
- They are present on the plasma membrane of the cell which further detect antigens and trigger a response to the immune system.
- They are secreted by the b cell which then circulate and detect floating antigens or toxins which further triggers a response to the immune system.
What is the relation between antigens and T lymphocytes?
T lymphocytes bind to MHC’s which are bound to antigens in APC’s.
The T lymphosyctes then stimulate B cells to take further immune response.
What are APC’s
APC (atingen-presenting cells) are cells that capture antigens from pathogens which further process them down into smaller peptide chains and then expressed on their surface bound to MHC’s.
What are MHC’s
MHC (major histocompatability complex) are proteins which bind to the antigens present on the surface of APC’s
What is the relationship between antigens, MHC’s, APC’s, T cells, and B cells.
APC’s are antigen-presenting cells which process self and non-self antigens into peptide fragments for then MHC’s to bind to and then get recognised by T cells. These T cells stimulate B cells for it to take further immune responses.
What are antibodies?
Antibodies are proteins that recognise antignes from pathogens and aid the immune system to take further response.
Antibodies are produced by B cells and are either:
- present on the plasma membrane of the B cells
- secreted to circulate around body fluids.
