Humoral Immunity And The Genrstion of Antibody Diversity Flashcards
What is the variable region within an antibody specialised for?
In the variable region the amino acid sequence varies from one Ig molecule to another to allow binding to various antigens
What is the constant region within a antibody responsible for?
The constant region is responsible for its effector actions such as activating complement and binding to phagocytes
What is the antibody made out of?
2 heavy chain and two light chain, those light chain can be either lambda or kappa
What is the complementary determining region?
These are hyper variable region on the variable region which is part of the V that bind to antigens.
Side note CDR3 is the most variable region
How is the CDR different in primary structure and tertiary structures
The CDR are separated when in primary structure but they are adjacent when in 3D form
The rest of the V structure form the framework allows all the CDR to face the antigen
How much antibodies are there and where do they rest?
The body generates 100million B cells and each generates a different random Ig. These B cells just sit in the lymph nodes not doing much.
What happens to B cells during infections?
During an infection a few B cell will happen to make Ig that can Bing to the foreign antigens which then result in the activation of the B cell and it multiply. This is colonal selection
How do B cells get activated
Activation of a B cell require its Ig to bind with a foreign antigen then we need help from CD4+ T helper cell and the cytokines released from said T helper cells
How many genes do we have coding for antibodies?
We inherit no complete Ig gene, it’s all segmented. By arranging these segments in different combination we can generate many Ig sequence.
What does the Germ line kappa light chain contain?
The kappa light chain have one constant region 35 variable region and 5 short joining segments
V1-v25…….j1-5…….C…..germ line DNA…..
The J segment are quite close to the C segment but the V segment are a long way away from the constant region on the DNA.
Where can a ending keys enzyme attach within the antibody gene segments?
There are binding sites after each V segment and one before each J segment.
How does the endonucleus enzyme work?
It will cut at random after one V segment and before one J segment. The free end then ligature together and join together.
This process is not splicing but dsDNA joining. This is due to the fact that the resulting segments are not one functioning gene.
How is gene diversity generated?
Gene diversity can be enervated by rearranging the gene segment.
We have 1C, 5J and 35V so the number of different variable is 175 (35*5)
What happens during recombination with V and J segment
How is junction so diversity created?
RAG recombinase cut and remove intervening DNA and ends are processed before joining together.
Exonuclease will mess around with the free ends before they are ligature together.
Terminal deoxynucleotidyl transferase randomly add a few nucleotides to the free end before they are added together. This creases junction all diversity
Why is TdT terminal deoxynucleotidyl transferase important?
They are important for generating Ig diversity, it is also important as a leukaemia marker l and a useful enzyme in genetic engineering
