Term
| Junctional Diversity only contributes variability to a single BCR region. What region is this and why? |
|
Definition
CDR3/hv3
Remember, junctional diversity is acquired in the joining of V/D/J regions in the antibody chains. Since CDR3/hv3 can be located in J regions, they are uniquely situated to effect junctional diversity. |
|
|
Term
| Provide a general description of how BRC component expression drives B cell development from stem-cells to mature B-cells in the bone marrow. |
|
Definition
Development is driven by the ordered rearrangements of Ig genes
1) First, HC is rearranged and expressed on cell surface as preBCR
2) LC rearranges and is expressed with heavy chain on surface
3) If B-cell survives negative selection (i.e. is NOT self-reactive), it gives rise to mature B cell that can leave the bone marrow.
**B-cell is check after IgH rearrangement (preBCR) and after IgL rearrangement (BCR) |
|
|
Term
| Explain how IgM and IgD expression correlates with B-cell maturation from pre B-cells to immature B-cells to active B-cells |
|
Definition
SHORT-
HC and LC are floating around (Pre-B-cell)
... IgM and IgD are assembled but still floating (Pre-B-cell)
....IgM goes to cell surface (immature-still in marrow)
....IgD joins it (when B-cell released into blood)
....IgM is released to induce more IgM (if antigen is found)
1) Pre B-cells contain heavy and light chains float around
2) HC and LC begin to organize into IgM and IgD floating around (CD19+ and CD20+)
3) Immature B cell forms with IgM at the surface (CD79 a and b +) and IgD floating around
4) Immature B cell is released from marrow into blood stream (naive at this point). Both IgD and IgM are at the surface (BCRs)
5) Naive BCRs move through blood and lymph tissue, and wait for their antigen.
6) IF, B-cell finds epitope on pathogen such as a bacteria, then the B-cell is activated- IgD stays on surface, but IgM is released into blood stream (producing more and more IgM). IgM pentamer/hexamer
IgM and IgD with the SAME VDJ rearrangement and same L chain (i.e. kappa or lamda) with V:J rearrangement are expressed on the surface |
|
|
Term
| Explain how you would produce a specific monoclonal antibody in the lab. |
|
Definition
1) Isolate Mature B cells from immunized mouse, each possessing specific V:D:J and V:J recombinations
2) Fuse B-cells with immortalized tumor cells called "hybridomas" and grow in culture, screening for specific antibodies.
3) Grow selected hybridoma and harvest monoclonal antibodies from specific B cell clone
4) Can humanize the antibody by genetic manipulation of the Fc portion |
|
|
Term
| How does IgH rearrangement relate to Burkitt's lymphoma? |
|
Definition
| Heavy chain rearrangement with the c-myc loci can lead to lymphoma. |
|
|
Term
| Where are HSCS found in humans? |
|
Definition
1) Primarily in bone marrow
2) Small # in bloodstream
3) Umbilical cord
4) Fetal Yolk Sac (different than adult?) |
|
|
Term
| What is the difference between B1 and B2 cells? |
|
Definition
BOTH are CD19+/CD20+/CD79 a and b+/CR2+/ IgM/IgD
1) B1 (CD5+, IL-5R, LFA-1) are more basic cells found in fetal liver, omentum, peritoneal and pleural cavity.
They are T-cell INDEPENDENT and are involved in mucosal innate immunity
2) B2 cells are found in bone marrow and lymphoid tissues
They are T-cell-DEPENDENT |
|
|
Term
| Explain the transition from Pro-Pre-Immature-Mature B cells. |
|
Definition
1) Pro-B cells become Pre-B cells when V:D:J rearrangement occurs in the HC and a "pseudo" LC is apparent (mediated by TdT and RAG genes)
2) Pre-B cells express an HC at the surface with a "pseudo" LC. They are also CD19+ and CD20+
They become Immature B cells when V:J rearrangement occurs in the LC (immature B cells express CD79a and b +)
3) Immature B cells express IgM at the surface and are CD79a and b +. They are susceptible to "Receptor Editing" of the LC (RAG-mediated)
They become Mature when they express BOTH IgM and IgG at the cell surface
4) Mature B cells express IgM and IgD at the surface with the SAME HC and LC rearrangements (co-expression via RNA processing)
Mature B cells can leave the bone marrow at migrate to lymph nodes. |
|
|
Term
| What is "Receptor Editing" and how does it relate to B-cell maturation? |
|
Definition
Immature B-cells are CD19+, CD20+, CD79a and b+ cells that enter the 2nd checkpoint (self-reactivity).
Receptor editing is a "RAG" mediated process that involves rearrangements of the LC in order to limit self-reactivity. |
|
|
Term
| What are the 2 primary checkpoints of B-cell maturation? |
|
Definition
1) Do Pre-BCRs express a HC and a "pseudo LC" with CD19+ and CD20+
2) Are Immature B-cells self-reactive (liable to Receptor Editing) |
|
|
