Antibodies and Gene Rearrangement Flashcards
What is adaptive immunity
It has memory and changes with both time and persistence of antigen.. The secondary response is stronger and more rapid that the primary response.
B cells
B lymphocytes begin in the bone marrow and mature in secondary lymphatic organs such as the spleen and lymph nodes. They produce antibodies and form the humoral (soluble) arm of the adaptive response
Function of the B cells
They produce antibodies and form the humoral (soluble) arm of adaptive response
What is the B cell receptor
A membrane bound IgM molecule that is associated with intracellular molecules that transmit an activation signal via phosphorylation.
What is primary naive response of B lymphocytes
The 1st immunisation with antigen which results in a rise in antigen specific low affinity IgM in blood peaking at 2 weeks post immunisation then diminishes rapidly.
How did T cells originate
T lymphocytes begin as immature lymphocytes that home to the Thymus gland where they mature into functional T cells.
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Function of T cells
Provide cellular adaptive immunity
What is the T cell receptor
The antigen receptor on T lymphocytes. It is an immunoglobin like surface molecule that is coded for by a separate gene locus. The TcR is associated with a number of surface molecule.
B and T
What are you born with
Massive repertoire of B and T lymphocytes. Each lymphocyte represents a different antigen specifity randomly produced by rearrangement of the genes coding for the antigen receptors.
What do B and T lymphocytes each have
Each with unique antibody randomly generated with stacastic repertoire. It generates as many combinatios in hopes of having right antibody (gene recombination)
True or false, all B and T cells are born with the same specifity
False, all born with different specifity, as they interact with different antigens - cross-reactivity.
Where are antibodies formed from
Repeated protein units called Ig domains.
What is the Ig fold
An Ig domain consists of two anti-parallel B-sheets made up on 7 or 9 B strands.
and what does it contain approx
What is the Ig protein domain fold called
B-barrel with ~ 110 amino acids
How is the structure of Ig protein important
It contains a stable shape which is soluble. The loops at the end are not constrained, which can allow amino acid sequences to change without changing the overalll stability of the protein fold.
What is the blue section and what is its function
It is a disulphide covalent bond which keeps the sheets of the Ig protein fixed.
What does the antibody molecule consist of
4 protein chains (2 light and 2 long/heavy) that are all made of repeating Ig domains. There are 2 domains in Light (l) chains and 4-5 domains in heavy (H) chain.
What does the Fc region do in the antibody protein structure
- Helps antibodies connect to the innate immune response.
- This region interacts with cell surface receptors called Fc receptors and some proteins of the complement system.
- This allows antibodies to activate the immune system.
What does the hinge region of the antibody protein structure do
Provides a degree of flexibility which enables the antibody to bind to multiple targets at various distances - which helps when the antibody might not be in the right place.
Y shaped antibody
Has two flexible arms and the antigen binding sites are located at the tip of the two arms.
What is the Y shaped antibody formed from
The N terminum domains of the L and H chains.
What are the five Ig classes that humans have
IgM, IgG, IgD, IgE, IgA
What is the default antibody that B cell makes
IgM
What is the membrane form of the IgM
B-cell antigen receptor (BCR)
The soluble form of IgM has what
10 antigen binding sites
IgM reacts strongly to what
Surfaces such as microbes through avidity binding.
What is affinity
When the sum of the attractive molecule forces at two surfaces exceeds the repulsive forces.
The higher the affinity, what happens
Fewer molecules are needed per unit volume to associate and dissociaate slowly.
Affinity is a quantitiative measure of what
The attractiveness of two molecules together.
If the measure of attraction very high (high affinity)…
No need for as many molecules in solution together
What is avidity
Results from multiple affinity contacts and is when 2 or more sites contribute. Like Velcro, the strength of binding can be orders of magnitude higher than individual affinities.
How is the antigen binding site of Ig and TcR formed
Formed from the 6 protein loop regions that connect the B-strands in the Ig domain.
How are there so many different antibody molecules that can be produced from so few genes
Gene rearrangement
Amino acid region is found in where
3 discrete regions called Complementary Determining Regions (CDR). These are the 3 loops that connect the strands in the 1st domains of the H and L chains.
Germ-line regions are segmented into clusters called what
Variable, Diversity, Joining and Constant regions
What are RAG1 and RAG2 (recombination activation gene) responsible for and where are they active
Rearrangement. Active in B and T lymphocytes
