Antibodies - Structure & Function Flashcards
What is an antibody ?
- also called an immunoglobulin
- serum glycoprotein
Where are antibodies made?
- made in activated B lymphocytes called plasma cells
What do antibodies do?
- interacts with foreign molecules called antigens
- renders foreign bodies more susceptible to damage & elimination
What are some structural features of antibodies ?
- heavy & light chains
- constant & variable regions
- antigen binding site
- hinge
- effector binding sites
Describe Heavy & Light Chains
- 4 polypeptide chains
- they form 2 pairs with N termini aligned
Define Epitope
epitope is the 3D surface on an antigen which interacts with the paratope on the antibody
Define Paratope
the 3D surface on an antibody which interacts with with the Epitope on an antigen
Define primary immune response
initial encounter with a new antigen
What happens with prolonged or subsequent exposure to an antigen ?
- larger & faster secondary immune response
What are some functions of antibodies ?
- neutralisation of toxins
- initiation of inflammation
- agglutination
- neonatal immunity
- opsonisation to enhance phagocytosis
Describe IgG
- crosses placenta
- antitoxin
- activates complement
- activates macrophage & polymorphs to remove bacteria
Describe IgD
- small antibody
- small amount in blood
- mostly present on mature B cell surface, where it may be involved in triggering cell division
What are some examples of antibodies ?
IgG, IgA, IgM, IgD, IgE
What are some direct diagnostic use of Ab?
- quantitation of antibody in blood enables identification of pathogen & monitoring progress of infection
- monitors body own immune response
What are some uses of purified Ab ?
- passive immunisation
- antiRhD
- delivery of other agents
- cleaning up bone marrow in leukaemia
Describe Polyclonal antisera I
- purify Ag
- immunise animal
- collect blood
- aspirate supernatant
- characterise
Describe Polyclonal antisera II
- cheap
- easy to obtain
- no need to kill animal
- cross reactivity can be a problem
- hard to standardise
Describe Monoclonal antibodies I
- immunise animal
- check titre
- sacrifice animal
- remove spleen, separate cells
- fuse cells with myeloma cells
- grow hybridoma cells
Describe monoclonal anitbodies II
- Can be difficult to obtain the require specifity
- single specificity = 1 epitope
- can be produced in bulk
- no change in properties
Define EMIT
Enzyme Multiplied Immunoassay Technique
