1.4 Antibody Diversity Flashcards
What region of the antibody binds the antigen?
Hypervariable region
What is a hinge region?
Allows antibody to bend and properly bind to a unique epitope
Examples of immunoglobin classes
IgG, IgM, IgD, IgA, IgE
- Different classes due to heavy chain
Light chains can either be __
Kappa or Lambda
Antibody structure characteristics
Compact, folded, and stable
Hypervariable regions are ___
At the tip of antibody that binds the antigen
What does antigen binding site diversity allow for?
Allows antibody to bind to any type of foreign structures
Binding of antibody molecule with antigen’s is a ___ bond
Noncovalent bond
Explain multiple antigen with different epitopes
Antigen can have different unique epitopes along it that different antibodies can bind to
Describe multivalent antigen with a repeated epitope
antigen has 1+ of the same epitope
2 types of epitope structure
Linear and discontinuous epitope
Describe linear epitope
Antibody recognized several amino acids in a row
Describe discontinuous epitope
2 regions interact to form a discontinuous epitope
- If you denature the protein, you’d destroy 3D protein structure and destroy its antigenic stimulation
Variable regions
Vh
Diverse regions
Dh
Joining regions
Jh
Heavy-chain locus regions and chromosome number
V-D-J
Chromosome 14
Lambda light chain locus chromosome number
22
Kappa light-chain locus chromosome number
2
Describe somatic recombination
- Occurs during maturation process of B cells in bone marrow
- DNA is looped out and lost and V, J, and C are combined
Process of recombination and 12/23 rule
12 chromosome is next to V
23 chromosome is next to J
RAG protein recognized chromosome 23 and 12 –> 23 and 12 are pulled together by RAG protein –> looped chromosomes are clipped off –> somatic recombination
Steps for junctional diversity
- Nuclease w/ RAG complex clips the heptamer
- Backbone forms a loop and creates DNA hairpins
- RAG opens hairpins by nicking one strand of DNA
- Creates palindromic P-nucleotides
- TdT lays down nucleotides
- Homology forms and ends are removed
- Gaps are filled by DNA synthesis
Overview of junctional diversity
D gene is joined to J gene with random nucleotides in the middle
- Encodes different proteins everytime
Why can the unique junctional complex cause problems?
You may or may not be able to transcribe L –> VDJ –> constant region (Cgamma)
Define allelic exclusion
Only 1 heavy chain and 1 light chain gene expressed per cell
- Heavy and light chain must work together to provide unique antigen specificity for each B lyn
Define allelic exclusion
Only 1 heavy chain and 1 light chain gene expressed per cell
- Heavy and light chain must work together to provide unique antigen specificity for each B lymphocyte
- Single antigen specificity per cell
What binds next to the B-cell receptor before the antigen binds?
Signaling proteins
IgBeat
Igalpha
Define naive B-cells
B cellss that are fully maturated but haven’t been stimulated by antigen
Describe IgM and IgG
- They’re signaling proteins that say the cells are mature and have a functional B cell
- Added after somatic recombination
Once B cells mature it leaves the ___ and goes to the ___ to see if there’s antigens to interact with
Bone marrow
Lymph nodes
Describe secreted IgM
Once IgM is stimulated by binding of antigen to surface, it switches from a C-terminus for transmembrane IgM to a C-terminus for secreted IgM
- This is done through RNA splicing
Hypermutation ___ variability
Increases
- Antibody affinity for antigen increases after stimulation of VJ or VDJ region is put through to hypermutation
- Hypermutation produces a molecule that binds antigen better
Hypermutations are induced by
Activation-induced Cytidine Deaminase (AID)
Secreted IgM is a ___
Pentamer
- 5 IgM molecules are hooked together by a J chain
Describe the process for switch sequences
- IgM and IgD are produced
- AID targets the S switch regions
- DNA in those switch regions is nicked
- DNA is looped and recombination
- IgG1 produced
The primary component in classical system of complement is
IgM
IgD doesn’t do anything, except
Get on the surface of naive unstimulated but mature B cells for cotranscription
Most abundant Ig in neutralization, opsonization, sensitization for killing by NK cells, sensitization of mast cells, and activation of complement system
Neutralization = IgG
Opsonization = IgG
Sensitization for killing by NK cells = IgG
Sensitization of mast cells = IgE
Activation of complement system = IgM and IgG
Ig in the following properties: Transport across epithelium, transport across placenta, diffusion into extravascular sites, and mean serum level
Transport across epithelium = IgA
Transport across placenta = IgG
Diffusion into extravascular sites = IgG and IgA
Mean serum level = IgG
IgA exists as a ___ on mucosal surfaces
Dimer
- has a joining chain
