antibody structure and generation of B cell diversity Flashcards
the 2 components of an antibody
fragment antigen binding (Fab)
fragment crystallization (Fc)
Antibody classes (heavy chain, light chain)
heavy: G, M, D, A, E
light: kappa and lambda (kappa is first choice during selection)
Are immunoglobulin chains folded into compact and stable protein domains?
Yes
what makes up the V domain (antigen binding domain)
heavy and light chain together
Do C domains have sequence variation?
No
what is the 3D structure of the Ig C and V domains
sammich
what are hypervariable regions?
loops
what are framework regions made of?
beta strands
what do VL and VH make
a composite site
which is a antigen binding site
complementarity determining regions (CDR)
and hypervariable regions (HV)
what is the epitope/antigenic determinant made up of?
protein or carbohydrate:
- glycoproteins
- polysaccharides
- glycolipids
- peptidoglycans
what are the destructive antigen binding sites?
autoimmune (lupus/DNA)
allergy (antibiotics)
what are multivalent antigens
antigen containing more than one epitope or multiple copies of the same epitope
which multivalent antigen would have stronger binding strength?
same or different epitopes
same epitopes because it would be more sticky and have stronger binding strength
what can epitopes bind to on an antibody antigen binding site
pockets, grooves, extended surfaces, or knobs
types of forces behind antigen-antibody interactions
non-covalent:
electrostatic
van der waals
hydrogen bonds
hydrophobic interactions
what is the affinity of antigen-antibodies interactions based on?
the strength of the interactions
where are monoclonal antibodies produced from
a clone of antibody-producing cells
what 2 things are antibodies useful tools for
specificity and affinity strength
4 types of therapeutic monoclonal antibodies
- mouse
- chimeric
- humanized
- human
specific example of chimeric and humanized Monoclonal antibody names and what it treats
chimeric: rituximab, b-cell non-hodkins lymphoma
humanized: trastuzumab, metastatic breast cancer
how is nearly limitless antibody variety achieved
a unique genetic organization from gene segments: that are families of alternative versions arrayed sequentially in DNA AND germline form/config.: which is inherited form of immunoglobulin genes
the variable region is comprised of what in both light and heavy chains
light chain: 1 variable and 1 joining segment
heavy chain: 1 variable, diversity and joining segments
does random recombination of gene segments produce diversity in antigen binding sites?
yes
what is the order of regions being joined together during recombination
diversity and joining regions first and then variable region after
which segment has the most variation
variable region in heavy chain, then kappa light chain and then gamma light chain
do light chains have any diversity region?
no
which segment has the highest amount of constant regions
heavy chain
are the amount of joining regions pretty similar between both chains?
yes
where are RAG genes made
in lymphocytes
are RAG genes active in any other cell type than lymphocytes?
no
are RAG genes important for functional adaptive immunity?
yes they are critical
is P nucleotide insertion palindromic?
yes
how is N nucleotides inserted
it is non templated and inserted by terminal deoxynucleotidyl transferase (TdT)
how is the antibody isotype determined
by the heavy chain
which immunoglobulin chains do all naive B cells start with
with mew and delta which are able to be expressed simultaneously
what determines expression of either IgM or IgD and at what level
differential splicing, RNA level
how many allele/copy is expressed in each B cell, and what is the result
only 1 and each B cell has a single antigen specificity
what makes the specificity of antibody response a central principal of adaptive immunity
the fact that each antibody has a single antigen specificity
what location is immunoglobulin first made on
membrane bound form that is present on B cell surface
which Ig is produced in large numbers: IgM or IgD
IgM is produce in large numbers
how are secreted antibodies produced and is rearrangement required
an alternative pattern of heavy chain RNA processing, no rearrangement necessary
how are rearranged V region sequences further diversified
somatic hypermutations by AID
what is affinity maturation
selection of mutated immunoglobulins with improved antigen-binding
what does affinity maturation do
allows the human immune system to keep up with the pathogen evolution
do the initially made IgM have limitations
yes, binds well to repetitive sequences, but has limited ability to clear
when does isotype switching occur
during an active immune response
what is isotype switching dependent on
during an active immune response done by cytokines.
(antigen-activated T-cell cytokine secretion)
what mechanism initiates antibody secretion?
RNA processing/splicing
what are the 2 ways antibodies aid in pathogen clearance
- neutralization
- opsonizing
does somatic hypermutation enhance affinity or avidity
affinity (single site)
when would IgG replace IgM
when there are 2 sites being of sufficient avidity
what Ig is responsible for the synthetization of mast cells
IgE
what Ig is responsible for transport across the epithelium
IgA
what Ig i most responsible for transport across the placenta
IgG1 (and IgG3,4)
where is dimeric IgA made
in the lymphoid tissues underlying the mucosal surfaces and is then secreted across them
is flexibility crucial for Ig molecules
yes, because it binds simultaneously to pathogens and to effector molecules and receptors of the immune system
types of movement on Fab arms
wave, rotate, wag, bend
which IgG subclass has high susceptibility of hinge to proteolytic cleavage
IgG3
which is the subclass of IgG that has different half life in serum
IgG3 (7 days) the rest have 21 days
