Lecture 12 Flashcards
When does B cell light chain rearrangement occur?
Light chain gene rearrangement occurs in pre B cell resulting in kappa or lambda light chain
What does kappa or lambda chain become?
IgM on surface
How do you know something is a B cell?
When you see IGM on cell surface you know it is a B cell
Antigen dependent/independent portions of B cell development?
What happens in marrow is antigen independent
What happens out of marrow is antigen dependent
Which B cells are innate like?
B1 and marginal
Describe B 1 and marginal B cells?
Not truly innate as they rearrange which is adaptive
Don’t require T cell help
Do not have memory
What is the classic B cell?
B2
Where is B1 made?
Fetal liver
Are B1 cells continually made?
No
Where are B1s found?
B1 cells primarily found in peritoneal and pleural cavity
Not found in blood or normal lymphoid tissue
Describe B1?
No isotype switch
Mostly against carbs
Do not use T cell help
Self renewing
Describe marginal B cells?
First line of defense
Made after birth
Like B1 cells but located in marginal zone of spleen
What happens if too little antigen is present?
May gain tolerance and not be able to respond later
What affects immongenicity?
Size - Bigger antigen bigger response
Route -
Ajduvent
Whey is insulin not immunogenic?
Too small
How big must something be to generate immune response?
10k daltons
Which routes are best for vaccination?
- Subcutaneous > intraperitoneal > IV or intragastric
Soluble or nonsoluble antigen generate better response??
Non soluble
Most common adjuvant?
Aluminum hydroxide, AKA alum
Two signals needed for B cell activation?
Signal one is taking up antigen through IGM
Signal two comes from T cell
What are T inidependent B cells?
T independent B cells are usually B1 cell type that recognize carbs
What happens to activated B cells?
B Cells become germinal centers which secrete plasma cells and memory B cells
B & T cell interaction?blem
They do not recognize the same epitope
B cells recognize native epitope
B cells recognize confirmation determinant not linear peptide
T cells recognize a peptide in context of MHC
T cells recognize linear peptide
Which B cell response do babies have?
T dependant
Do not have T independant so cannot react with carbs
This is problem with hemapluous flu as it is carb
What does tetansus toxoid do?
Attaches to carb portion of flu so baby immune system can recognize tetanus protein portion
T cell will then react protein portion activating B cell
In this way baby has tricked immune system to making T independant response even though they cannot generate one
How are proteins and carbs handled in B cell?
Proteins - t dependent antigens
Carbs - T independent antigens
How does secondary response increase affinity?
Somatic hypermutation
What is required for class switching?
AID
B cell starts out as IgM/IgD
Need aid to switch
Where does isotype switch occur?
Germinal center
Two dypes of somatic rarrengment?
Isotype switch
VDJ rearrangement
What is required for rearrangment?
Rag1/2
What can happen in germinal center?
Isotype switch
Rearrangement
Memory cell development
Plasma cell development
What happens in dark and light zone of germinal center?
Dark zone - mutation occurs here
Light zone - mechanism where B cells with high affinity occur here
What happens to low affinity or self reactive B cells?
If cell is low affinity or self affinity it will not be activated and will die
BCR will not be cross linked so it cannot present antigen to T cell and will die
What happens to low affinity or self reactive B cells?
If cell is low affinity or self affinity it will not be activated and will die
BCR will not be cross linked so it cannot present antigen to T cell and will die
What do follicular dendritic cells do?
Found in germinal centers & carry antigen for B cell to present to T
Found in light zone and have antigen on surface
B cell will respond to this and take it up if there is a match to present to T cell
What must B cell in germinal center do for survivial?
For the B cell to be selected by T cell for survival, it must present something to T cell
What are TI antigens?
TI antigen - T independent most likely a carbohydrate
TI response have no germinal centers are there are no T cells
No memory, mutation, or isotype switch
They can make plasma cells but only IGM
What are TI antigens?
TI antigen - T independent most likely a carbohydrate
TI response have no germinal centers are there are no T cells
No memory, mutation, or isotype switch
They can make plasma cells but only IGM
