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40 Cards in this Set

  • Front
  • Back
CD79a/CD79b heterodimer
- Associated with B Cells
(membrane Immunoglobulins)
- CD79a/b anchors B-cell receptors to the membrane
Light Chains on B cells have what kind of segments?
Variable and Joining (V and J)
Heavy Chains on B cells have what kind of segments?
V, D, J
Variable, Diverse, Joining
Somatic Recombination
process of constructing a variable region of immunoglobulin
- D& J combine first, and then V.
Allelic exclusion
successful rearrangement of heavy chain variable region on one chromosome, inhibits somatic recombination of heavy chain variable region on the other member of chromosome pair
What occurs at the Pro-B Cell stage?
- Transcription of RAG1 and RAG2
- CD79a/CD79b are linked to intracellular signaling mechanism
- no immunologically relevant molecules present
Pre-B Cell Stage
- Pre-BCR is expressed on cell surface
- CD79a/Cd79b is also on cell surface
- initial transcription of μ heavy chain

- allelic exclusion - when getting chromosomes from one parent, must inactivate the other
Immature B-cells
- pre-BCR -> BCR (IgM) = fully functioning Ig
- BCR has 2 μ heavy chains
- initial transcription of kappa and lambda light chains
- tolerance induction
Naive, mature B Cells
- Alternative Splicing - can produced different constant regions of cell surface antibodies

- Mature B-cells leave bone marrow, enter blood stream, migrate to peripheral lymphoid tissue, recirculate if don't encounter antigen in secondary lymphoid tissue
-cell surface has Cd40, cd21 cd81 cd45
vascular molecules. control homing of B cells
Alternative Splicing
process by which hnRNA encoding variable region (VDJ) of heavy chain is spliced to either μ or δ constant region to form IgM or IgD
What molecules comprise the B cell receptor complex (BCR)?
mIg (membrane immunoglobulin)
What stage does the B cell acquire its antigen specific receptor (membrane Ig)?
antigen bind contact site (other end of epitope
What kind of molecular force is the antigen-antibody interaction?
what gives the essential signal for the formation of germinal centers?
CD40 Ligand
What are germinal centers associated with?
- B cell clonal expansion
- Isotype Switching
- Affinity maturation
- Differentiation into plasma cells and memory cells
Which secreted Immunoglobulin is responsible for the negative signally of B Cells?
binds to FcγRIIB - low affinity receptor
How is secondary immune response different from primary immune response?
- Secondary
- can occur anywhere in body (outside of secondary lymphoid tissue)
- Higher Antibody titer (much more progeny ~1 log greater)
- less lag for:
affinity maturation, differentiation to plasma cells and migration to follicle cells,
enhances the immune response
- added to vaccines
polyclonal activator. can trigger proliferation of many clones of lymphocyte B.
Factors that participate to effect antibody specificity
- Multiple germline genes
- Combinatorial association
- Junctional Diversity
- Random selection of the light and heavy chains
adhesive molecules on B-cells that interact with addressin (in high endothelial venules) to mediate exit from blood to peripheral lymph nodes
X-linked Agammaglobulinemia (Bruton's)
- mutation on BTK kinase
- BTK kinase plays a critical role on B cell activation, differentiation and proliferation
- initial defect occurs between the pro-B and pre-B transition
Expressing HLA-DR3 and HLA-DR4 is a predisposition for what disease?
Diabetes Mellitus (Type I)
Expressing HLA-B27 is a predisposition for what disease?
Ankylosing Spondylitis
Expressing HLA-B8 and HLA-D23 is a predisposition for what disease?
- stomach pains
- Coeliac Disease
Where does the entry of memory B cells into lymph nodes occur? Why?
At afferent lympatics rather than high endothelial venules (HEV’s).

Because they lack L-selectin. (needed to go from blood to lymph at HEV)
Which molecules are required for optimal activation of B cells?
CD40/CD40 ligand
Btk kinase
What are T-independent antigens? What is produced?
They are antigens that don’t need a T-cell for them to be recognized by B-cells.

IgM is produced.
What are the types of T-independent antigens? Difference?
Type I and Type II

Type I - only IgM. no isotype switching

Type II - some isotype switching
Which heavy chain variable regions are excised? What are you left with?
Mu and Delta are excised, leaving alpha, epsilon or gamma heavy chain constant regions.
What is the difference between B cells and plasma cells?
B cells express antigen specific antibodies as cell surface receptors.

Plasma cells secrete antibodies.
Which interaction is essential for the formation of germinal centers?
CD40/CD40 ligand interaction
What is the process that activated naïve B cells undergo within 24 hours of immunization? What happens?
Clonal expansion.
Activated B cells and T cells migrate to the primary follicles where enhanced proliferation of B cells leads to the formation of germinal centers
What mediates the exit of B-cells from the blood?
L-selectin, an adhesive molecule that is present on the B-cell.

It interacts with vascular addressin molecules on the high endothelial venules (HEV).
What is the net effect of allelic exclusion?
All mIg present on the surface of any one B cell will have the same heavy chain variable region
What mediates the incorporation of nucleotides at junctions?
terminal deoxynucleotidyl transferase-
A template independent DNA polymerase
What are the naïve mature B cell heavy chain constant regions called? Light chain?
The heavy chains are known as mu and delta.
The light chain constant regions are either kappa or lambda.
What comprises the BCR?
The heterodimer CD79a/CD79b.
Two identical heavy chains and two indentical light chains linked by a disulfide bond.
Each chain is made up of a variable and constant region.