Anti Bodies Flashcards
General structure of antibodies what stabilises it
Quaternary structure, 2 light chains and two heavy chains stabilised by disulphides bridges bridges between shapes forming the characteristic Y shape
Two main regions of antibodies, which one is used for antigenic recognition of pathogens
We have a constant fraction, where sequence is identical for each antibody of a specific isotope (A,G,E,M…) and variable fraction, which is responsible for specificity towards specific antigen of specific pathogen
What the constant region used for? And the variable region?
Variable region is responsible for the antibodies specificity constant region is important for effector functions, and joining with surface cell receptors
what is the Fc region of the antibody
The Fc region is the crystalize able fraction of the antibody, also known as the constant fraction. Only varies between different isotypes and its used for interactions with surface receptors and determining effector functions
What is the Fab region
The antigen binding fraction which also contains the variable regions that give antibodies their unique specificity
Name the two regions that make up an antibody
Constant regions and variable region
Who determines the specificity of an antibody
The variable regions, or the Fabs of the antibodies containing the CDR loops (3 on heavy and and 3 on light). Thanks to somatic recombination
Name two proteolytic enzymes used in antibody modification
Papain and pepsin, Used to generate fragments with a modified function (from antibodies)
What does PaPain cause
proteolytic Cleavage of antibodies removing Fab regions, generating 2 Fab fragments and 1 Fc fragment
Pepsins mechanism of action
Proteolytic cleavage of generating a fragment composed of only two Fab regions, this cleavage also breaks down the Fc portion of the antibody into peptides, generating peptides and and F(ab)2 fragment
Nomenclature of fragment generated by Pepsin
F’(ab)2
Is the hypervariable region on what terminal of polypeptide
N terminal of polypep chain
what are antibodies classified by
Classified by constant fractions of both light and heavy chains. Heavy chain FC–IgM, A, E, D, G, and light chain FC- Kappa and landa where landa is more common due to isotypic exclusion
what antibodies team up forming dimers or pentamers how do the join to each other, and which ones have an extra constant region
IgA’s forming dimers and IgM’s forming pentamers ( big and slow one of reasons IgM is not a gent opsonizer) IgM and IgE have extra CH region
Isotypes of light chain constant regions, are they both produced in a particular b cell?
Kappa and landa, NO thanks to isotypic exclusion (allelic exclusion) in a particular b cell only one isotype is being produced.
What are the effector functions for antibodies
Neutralization (with agglutination), complement activation, Opsonization, ADCC
what antibody has 4 subclasses
IgG, subclasses 1,2,3,4
main antibody in acute immune response
IgM
most abundant serum isotype
IgG 70-89% and M is 5-10%
Epitope
Region of antigen that binds to paratope on antigen, also called the antigenic determinant, Two type linear and conformational determinants. Tip; there can be different epitopes on one antigen—relate to monoclonal antibody screening process
antigenicity
the ability of an antigen to bind to a specific antibody or t cell receptor,
immunogenicity
The ability of an antigen to generate and immune response, specifically through the activation of lymphatic cells, antigens that can do this are also called IMMUNOGENS
Haptens
antigen that are not immunogenic on their own, need to associate with molecules called “carriers” in order to create an immunogenic response
Paratope
Region on Fab the binds to epitope of antigen
IgD, how common is it in serum
Not common, mainly found bound to b cells as BCR’s
what are IgEs mainly involved in
IgE are mainly involve in the allergic response and helminth immune responses
What are IgM’s functions
IgM’s are the main antibodies in an accute immune response, mainly for pentamers joined by J chains
Types of epitopes or determinants
Linear determinants and conformational determinants
what’s responsible for the high variability of the antigen binding regions, when does it occur
somatic recombination occurs during maturation of b cells, we see recombination’s between D J sequences and D V sequences on heavy chains and DV sequences on Light chains, combines generate billions of possible antigens for any pathogenic antigen the body can encounter
what’s the difference between Light chain and heavy chain somatic recombination
The variability, heavy chains have up to 9,000 possible recombination’s while the kappa and alpha have 200 and 270 respectively. A lot more variability can be achieved on the heavy chain thanks to the fact that they have the joining regions which are also involved in the recombination
What are CDR`s…What do they determine
The determine the antigen specificity of an an antibody (the paratope of the antibody) also known as complementary determining regions.
Structure of CDR`s , where on the antibody are they
On Fab, forming part of variable regions, The form loops at the tips, 3 from light chains and 3 from heavy chains
Immunogen
An antigen that is immunogenic, no all antigens are immunogenic
What types of molecules are the best immunogens
carbohydrates and glycoproteins ( peptides most, those are the one incorporated in HlA)
Antibody maturation
Occurs in already differentiated b cells and we see somatic hypermutation in which we see improvements to paratope specificity and overall function, and isotype recombination in which IgM’s are converted to IgG,A,or E
