Bursa/Bone Marrow-Derived Cells (B Cells) Flashcards
How many B cells are produced daily? (in humans since we don’t do animals in this fuck-tarded class)
a billion (1.0*10^9)
T or F?
B cell lymphopoiesis occurs throughout the lifetime of all animals.
FALSE because it’s not all animals (invertabrates don’t have B and T cells).
It is TRUE for mammals though…
Amount produced decreases with age, hence why old farts are eventually immuno-suppressed.
What percentage of recirculating lymphocytes do B cells constitute?
10%-25%
How long do mature B cells survive without encountering their antigen?
A few days or weeks [short-lived cells].
Which B-cells are long-lived cells?
Memory cells…. hence being a memory.
The B cell expresses up to ____________ BCRs.
500,000 BCRs
True or False. All the BCRs on a single B cell have the same constant region.
FALSE. THey have the same variable region.
What are the two roles of the BCR?
1) Delivery of activating signal
2) Triggering endocytosis leading to processing for presentation to T-cells
The molecules that transduce the activation signal from an activated BCR.
CD79 molecules.
The molecules required for the surface expression of IgM and IgD.
CD79 molecules.
True or False. The rearrangement of Ig heavy chain (IgH) gene must occur before that of the Ig light chain (IgL).
TRUE. If IgH fucks up the IgL will not take place.
What chromosome are IgH genes on?
Chromosome 14 –> 200 Vh; 30 Dh; 6 Jh; 9 Ch; (h means heavy)
What chromosome are the IgL KAPPA genes on?
Chromosome 2 –> 100 Vk; 5 Jk; 1 Ck; (k means Kappa)
Which light chain arrangement occurs first? If that does not work then what takes its place?
KAPPA comes first and if that doesn’t work LAMBDA.
What chromosome are the IgL LAMDA genes on?
Chromosome 22–> 100 Vl; 6Jl; 4Cl; (l means LAMBDA)
True or False. One B cell will react with more than one antigenic determinant and will produce multiple antibodies, one for each antigen.
FALSE. They interact with ONE antigen and produce antibodies ONLY FOR THAT ONE.
True or False. This is very important for your clinical practice later in life.
FALSE. This is all a crock of shit and a waste of time.
How many BCRs does an individual possess?
1*10^11 BCRs –> 100 billion
What three mechanisms account for BCR diversity?
1) Somatic recombination of multiple germline gene segments
2) Junctional diversity: Base deletion; P-nucleotide and N- nucleotide additions
N-nucleotides: TdT is expressed by PRO-Bcell ONLY DURING THE STAGE OF IgH rearrangement.
Therefore, only IgH shows N-region Diversity.
3) Combining of identical IgH chains with different IgL chains. (Kappa and Lambda)
Stromal cells interact direclty with __(1)_____ and ___(2)____, providing them with cell-bound __(3)______
1) PRO- bcells
2) PRE- Bcells
3) survival signals
Cytokine supporting B-cell development.
IL-7
PRO- Bcell expresses ____ and ____ signaling molecules
CD79 – Ig-alpha and Ig-beta
True or False. PRO-Bcell express RAG enzymes and TdT?
TRUE.
True of False. Pro-Bcell Igµ gene arrangment occurs?
TRUE. Dh to Jh rearrangement followed by Vh to DhJh rearragement.
–> Once the Vh to DhJh occurs its a PRE-Bcell
True or False. PRE-Bcell express RAG enzymes and TdT?
FALSE. TdT activity has stopped but RAG enzymes are still getting it on.
What does a PRE-B Cell receptor consist of?
IgM Heavy chain
Surrogate Light chain
Ig-alpha and Ig-ß molecules
Can a PRE-B cell continue to develop without PRE-BCRs?
No.
What does the surrogate light chain consist of?
Two invariant proteins:
VpreB & lambda-5
What 4 things does the PRE-BCR do?
1) survival and proliferation of pre-B cell
it signals that it’s good-to-go and prevents apoptosis
2) inhibition of Vh to DhJh rearrangment of the heavy chain allele
its says stop that, we’re moving on to bigger and better parts of development
3) terminations of the surrogate light chain transcription
again, it says we’re moving on and don’t need this crap anymore
4) initiation of light chain[kappa, then if not successful lambda] gene rearrangement
it says lets move the fuck on
When does a PRE-B Cell become an IMMATURE B cell?
Once its BCRs become IgM with heavy chain AND light chain (not surrogate light chain). It will shed any left over PRE-BCRs and become the IMMATURE B Cell.
What happens if a BCR expresses high affinity for self antigen in the bone marrow?
One of three things:
1) It dies by apoptosis
2) Becomes ANERGIC
3) Receptor editing
What is receptor editing?
When the BCR expresses too much affinity and instead of dying it tries to correct the mistake.
RAG enzymes are RE-activated and LIGHT chain is acted upon.
True or False. TCRs and BCRs undergo receptor editing?
FALSE MOTHER FUCKER! Only BCRs do.
Where do IMMATURE B cells go?
to the SPLEEN for further development
Where do B Cells mature?
in the SPLEEN!
What makes a MATURE B Cell so mature?
the expression of IgM and IgD on their cell surface
True or False. A MATURE B Cell is the same as NAIVE B Cell?
True…. bitch.
True or False. The IgM and IgD express the same antigen specificity?
TRUE. They use the same VDJ exon and have identical light chains.
What makes up the B cell coreceptor complex?
CR2 (CD21)
CD19
CD81
What complement component does CR2 bind?
C3d.
C3d is a product of C3b being cleaved by Factor I once Factor H binds to it.
How does C3d bind to a B cell?
C3d picks up/binds antigen then C3d binds to CR2 while the antigen binds to the BCR