Antibody Synthesis Flashcards
What is somatic recombination? Where does it take place?
Takes place in every B lymphocyte
Assembling different fragments of DNA to create completely new immunoglobulins (diversity)
What do light chains exist as?
Multiple V and J segments upstream of a single C segment
What do heavy chains exist as?
V, D, J and C segments
How are these building blocks put together in heavy chains?
D segment joins a J segment (DJ), then the recombined DJ joins a V segment (VDJ)
Only one segment of each gene is needed and forms the variable and Fc region for heavy chain
What is function of constant (C) segments?
Alpha, delta, gamma, epsilon, mu (IgA-D-G-E-M) so determines class
Involved in Ig switching
Not actually part of antigen binding site
What does the variable region house?
The antigen binding sites - building blocks are V, D and J segments
What is somatic hypermutation?
Mutation in V, D and J gene segments are very high
When does somatic hypermutation occur?
After first B cell activation in lymph node
What does somatic hypermutation cause?
Worse, equal or better binding to antigen
What happens to clones expressing higher affinity?
Receive more stimulation than others so will divide more, causing more high affinity a antibodies to be produced
How many segments are there to choose from when building heavy chain?
46 V, 23 D, 6 J segments
What will happen to B cells with a higher receptor affinity for pathogen?
Positive selection (immature B cells have low affinity but mature B cells have high affinity for pathogen)
