Antibody Function Flashcards
What are the two jobs of antibody?
Recognise Ag and help eliminate it or eliminate it on their own
2 ways to find Ab are:
Transmembrane and secreted
Regions of secreted:
Fab binds Ag, Fc is tail
Which bit of Ab interacts with Ag? how?
CDRs have AAs complementary to Ag Epitope
What size should the epitope be?
About 2.5nm^2
Can more than 1 ab bind a pathogen?
Yes - different epitopes
What are discontinuous epitopes?
When binding a protein Ag, the tertiary structure is important (conformation rather than sequence)
How many CDRs used in binding?
Usually all 6 contribute, some are more important
4 forces involved in Ab Ag binding:
H bond, Electrostatic, VdW, Hydrophobic
Property of these bonds:
Reversible so need close interaction
What is multivalent bonding, why is it better?
When both fab arms of 1 Ab or 5/6 of a polym Ab bind - stronger
Amount of Ab in order
GAMDE
How do you switch from membrane to secreted Antibody?
in the Cmue bit, mue 1 and mue 2 exons encode a stretch of hydrophobic AA - antibody gets stuck to cell surface
If plasma cell - stop using them so secreted
3 things Antibodies can act on their own to do:
Neutralise Bacterial Toxins
Block viruses binding to their cellular receptor
Block adherence of bacteria to mucosal surfaces
What do antibodies mainly do?
Bridge between Ag and other cells
Which antibodies are good at direct neutralisation?
IgM, IgA, IgG
How do RBCs clear immune complexes?
Have CR1 which recognises C3b to Ab/Ag - clears it
Example of opsonisation by Ab
FcgammaR on phag cells bind IgG on path - engulf path
Which antibodies activate complement?
IgG and IgM
Killer cells and Ig?
FcR recognises Ab on path - kills it
Which Ab contributes to inflammation? how?
IgE - mast cells
What is the most abundant antibody in blood?
IgG1
Which Abs can cross placenta?
IgG1, IgG3 and 4
What does IgA do?
protects mucousal surfaces
