Immunology - 22 Flashcards
Which genes encode the light chain variable region?
V and J (not D)
Dear mature B cell only expresses what isotype?
IgM
All of the B cell’s progeny will produce antibodies and BCR’s that bind the same antigen. Why?
Because gene rearrangement of the variable region is permanent
What is negative selection and where does it take place?
It is a checkpoint that takes place in the bone marrow.
- All developing B cells are checked to see if they recognize self antigens
- if they do, then the cell gets a do over to rearrange its variable region genes (called receptor editing)
- if BCR recognizes self antigen, it undergoes apoptosis
When does receptor editing/negative selection take place?
After light chain rearrangement in the immature B cell stage
When will isotype switching take place?
Not until a B cell has been exposed to antigen
What is the defining characteristic of a mature but naïve B cell?
The presence of BOTH IgM and IgD on the surface
What happens of the B cell does not bind its cognate antigen in 2 to 8 weeks?
It will undergo apoptosis
Once the BCR binds antigen in the secondary lymphoid organs, the cell activates and the cell and the receptor itself will undergo which additional changes?
1 - clonal expansion (makes lots of copies of itself to build up the Army’s numbers)
2 - undergo affinity maturation (refinement of antigen binding site to increase affinity)
3 - isotypes which (choose the correct isotype for the battle)
4 - career decide (plasma cell - antibody secretion factory, or memory cell - recirculates)
If we have a B cell in the neck lymph node and it encounters A. pyogenes, what kind of isotype will it be triggered to produce? How about of it encounters tree pollen?
A. pyogenes - IgA
tree pollen - IgE
Where do B cells meet antigen?
Secondary lymphoid organs
