B cell activation #2 Flashcards
(46 cards)
What is allelic exclusion?
one allele of a gene is expressed while the other is silenced (It makes one LC + one HC)
Without it you will have Ab with multiple specificities.
What is heavy chain rearrangement?
@ B cell
Heavy chain –> is productive –> could be maternal mui or paternal mui
if second time doesnt work: apoptosis
What is light chain rearrangement?
@ Pre- B cell
Heavy chain –> isnt productive –> made again
Can be rearranged x4
paternal: kappa + mui
maternal: kappa + mui
What is isotype switching?
Changing from IgM to another isotype (IgE + IgA + IgG)
Does switching isotypes change specificity?
No (even if you rearrange it can bind to what it needs)
What does isotype switching need?
switch regions + T helper cells
Where does isotype switching take place?
germinal centers of secondary lymphoid organs
What enzymes needed for isotype switching?
AID –> activation-induced cytidine deaminase
Where is the switch region found?
in front of mui + in front of gamma
Why is there no switch region in front of delta?
Because when making mui you need delta
What are the 2 T cell signals needed to get cytokines for isotypes?
- SIGNAL 1: MHC signaling with APC B cell
* SIGNAL 2: CD28 – B7
What cytokines released to make IgG?
IFN gamma
What cytokines released to make IgE?
IL4
What cytokines released to make IgA?
Tgf-beta/APRIL/BAFF
How is diversity generated?
Random assortment
What are examples of diversity? (3)
Permutations in V-D-J genes for H.C and V-J genes for L.C. (You have rearrangement of heavy + light chains)
Pairing of different H.C. and L.C.
Recombination process by imprecise joining junctional diversity
What is junctional diversity?
Joining of V,D and J (small no. nucleotides can be added/ deleted)
What is somatic hypermutation?
Mutations that occur in the V, D or J segments
What is the affinity maturation in primary + secondary response?
o Primary response: Antibodies have a lower affinity
o Secondary response: there is somatic hypermutation and affinity maturation which means= > Ab + Ab has higher affinity for antigen
What segments are found in alpha, gamma, delta and beta TCR?
Alpha + gamma: VJC
Delta + beta: VDJC
How is alpha chain made?
- Joining: V+ J joining
- Transcription -> Primary RNA transcript made
- Splicing -> mRNA made
- Joining: VJ put together + C
- translation
- Then protein made: alpha chain
How is beta chain made?
- Joining: V+ J joining
- VDJ formed
- Transcription -> Primary RNA transcript made
- Splicing -> mRNA made
- Joining: VDJ put together + C
- translation
- Then protein made: beta chain
What is immunization? And how do we do it?
Provide individual with long-lasting immunologic protection again infectious agents
They slightly from infected -> put in healthy -> immunity (slightly infected called Inoculated)
What is components of natural acquired passive immunity?
IgG –> placenta
IgM –> after birth
IgA -> breast milk
IgG > as we grow + IgA (
