B Cell Lymph Development Flashcards
Which cells in the bone marrow do B cells and T cells come from then lymphoid progenitor
Pluripotent haematopoietic stem cells
Lymphocytes are constantly made but does it slow with age
Yes
What determines if something becomes a B cell
Stays in the bone marrow and also TF like pax5
What does tf pax5 do to determine it B cell
Rearrangement and expression of ig genes
Give an example of a specific B cell marker
Cd19
Once B cells have markers like cd19 what can happen
Clonal deletion
Where does B cell final development occur
Peripheral lymphoid tissues
What does a B cell precursor do as well as express pax 5 which sends signals to say it’s a B cell
It interacts to bone marrow Stromal cells via adhesion. Sends signal
After clonal deletion occurs. Which Bcells survive in periphery
Those who bind an antigen and undergo clonal expansion Eg into memory
What characterises a pro B cell (before pre)
Heavy chain rearrangements (only hc present) and no functional receptor.
Are both Heavy chain chromosomes checked at the pro B cell level and what happens
Yes. If both are unsuccessful in rearrangement the pro B cells die
What characterises a pre B cell
The h chain rearranged, pre B cell receptor
Which heavy chain in encoded first Eg in pro B cells, pre B cells
C mu (igm)
What makes up a pre B cell receptor
The igm h chain rearranged first
Then a surrogate light chain made from Vpreb and lamda 5 proteins (also rearrange)
What associated with the pre B cell receptor vpreb,lamda 5 and the Heavy chain
Ig a and ig b
If an ag is able to bind to the pre B cell receptor , what does this signal
To turn rag genes off for h rearrangement, the vpreb and lamda 5 are stopped expressed. Rag turn back on to rearrange light chain
How many turns does light chain have to rearrange in immature B cells
- 5 goes on each chromosome = 2x kappa
2 x lamda if kappa unsuccessful
Why can each chromosome rearrange 5 times
There are 5 Jk genes
What happens if all 20 light chain rearrangements fail
The immature B cell dies in bone marrow
What 2 things can happen if immature B cells are self reactive
Clonal deletion or receptor editing
What is receptor editing
Further light chain rearrangements to make them less self reactive
Why does reaction to soluble self antigens not cause apoptosis clonal deletion
There is less of a signal to bcr so they escape the bone marrow but are down regulated. This means a lot of antigen needed to stimulate them
What are B cells called which were down regulated by soluble self antigens
Anergic b cells
What are B cells which still go to periphery because they are low affinity binding to self antigens
Clonally ignored B cells
