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53 Cards in this Set
- Front
- Back
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Where does B cell development mainly occur?
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Mainly in the bone marrow
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Progenitors committed to the B-cell lineage give rise to pro-B cells as a result of what?
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The direct interaction of stromal cells.
VCAM-1 adhesion molecule on the stromal cell and the VLA-4 adhesion molecule on the pro-B cell. Other cell adhesion molecules (CAMs) are also involved. |
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Once contact has been made between VCAM-1 and VLA-4, what is the receptor on pro-B cells that interacts with stem cell factor (SCF)?
Where is SCF located? |
C-kit
located on the stromal cell surface |
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What interleukin drives the maturation process of B cells?
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IL-7
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IL-7 receptors are on what stage of B cells?
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pre-B cell
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T/F
Adhesion molecules on the pre-B cells are upregulated allowing the pre-B cells to detach from the stromal cells. |
False!
Adhesion molecules on the pre-B cells are DOWNregulated allowing the pre-B cells to detach from the stromal cells. |
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T/F
IL-7 is REQUIRED for continued growth and maturation to the immature and mature B-cell stages. |
True!
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What cells, that provide microenvironments for B cell maturation, are nonlymphoid cells located in the bone marrow?
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Stromal cells
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What are the 2 primary functions of stromal cells?
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1. Interact directly with pro-B cells and pre-B cells
2. Secretion of several cytokines, including IL-7 (IL-7 supports the developmental process of B-cells. |
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Immunoglobulin genes are (single/multiple)-gene segments in the germ-line DNA.
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Multiple
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Are immunoglobulin genes carried in germ or somatic cells?
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Germ cells
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When does the rearrangement of immunoglobulin genes into functional genes occur?
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During the B-cell maturation process
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What is the earliest identifiable cell in the B-cell maturation process?
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Pro-B cell
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The heavy chain V(H) to D(H)J(H) gene rearrangement occurs in the (early/late) pro B-cell.
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Late
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The heavy chain D(H) to J(H) gene rearrangement occurs in the (early/late) pro B-cell.
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Early
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After heavy-chain rearrangement of the pro-B cell is completed, what type of cell is it?
What does the B cell begin to express at this stage? |
Pre-B cell
a μ chain |
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The large pre B-cell expresses what receptor?
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Pre B-cell receptor
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The membrane μ chain in pre B-cells is associated with a surrogate (light/heavy) chain and what polypeptides?
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Light; Ig(alpha) and Ig(beta) polypeptides
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T/F
Surrogate light chains are true Ig proteins. |
False!
They are NOT true Ig proteins |
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T/F
The membrane μ chain is expressed only in primitive B cell precursors. |
True!
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When does the cell halt heavy chain gene rearrangement and begin light chain gene rearrangement?
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In small pre B-cells, when the μ chain and surrogate light chains reach the cell surface, it is believed that a signal is transducted back to the cell, indicating that a functional heavy chain protein is present.
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In the small pre B-cell, when the μ chain and surrogate light chains reach the cell surface, why does the pre B-cell receptor disappear from the surface and the μ chain become trapped in the ER?
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Because the production of surrogate light chains stops
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The transition between which two stages requires light chain gene rearrangement?
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Pre B-cell to immature B-cell
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T/F
Multiple light chain isotypes are expressed on the membrane of a B cell. |
False!
Only ONE light chain isotype is expressed on the membrane of a B-cell. |
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What are the 2 possible light chain isotypes?
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Kappa and lambda
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a) What commits the immature B cell to a particular antigenic specificity?
b) This is determined by what sequences? |
a) Completion of the light chain gene rearrangement
b) Heavy chain VDJ sequence and light chain VJ sequence |
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What Ig is expressed on the cell surface of immature B-cells?
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IgM
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The development of immature B-cells to mature B-cells involves the production of 2 mRNA's. What does each one code for?
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One for the μ chain and one for the delta chain
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Development of immature B-cells to mature B-cells involves coexpression of which 2 Igs?
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IgM and IgD
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Early mature B-cells express low levels of IgD. When does expression of IgD increase?
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After the cells are exported from the bone marrow to the lymphoid organs
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What percent of B-cells produced in the bone marrow are actually recruited into the B-cell pool?
Why? |
Only 10%
Due to negative selection |
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Describe negative selection in B-cell development.
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When immature B-cells react to self antigens, crosslinking of the membrane autoantibodies occurs, leading to apoptosis.
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T/F
If a B-cell receptor is self-reactive, the cell immediately undergoes apoptosis. |
False!
First, the cell becomes arrested in development and continues light chain gene rearrangement (with low cell surface IgM), resulting in new receptor specificity. If it is still self-reactive, then it will undergo apoptosis. If not, the immature B cell will migrate to the periphery and mature. |
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What subset of B-cells does not conform to the normal pathway of development?
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B1 cells
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B1 cells are characterized by the expression of what on their cell surface?
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CD5, a cell-surface glycoprotein usually considered a T-cell marker
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B1 cells precede the development of what type of cells?
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B2 cells, which are the majority subset of B cells
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Do B1 cells have IgD on their cell surface?
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They have very little or none
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B1 cells arise from a stem cell that is active when?
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During prenatal development
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a) Rearranged heavy chain genes are more diverse in (B1/B2) cells.
b) Therefore, antibodies produced by (B1/B2) have low affinity and bind to many different antigens (polyspecificity). |
a) B2
b) B1 |
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B1 cells contribute to the production of antibodies that are against what?
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common bacterial polysaccharides, NOT protein antigens
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How are B1 cells maintained in the adult, since B1 cells are no longer developed in the bone marrow?
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Maintained through self-replication in the peripheral circulation
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Self-renewal of B1 cells is dependent upon which cytokine?
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IL-10
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Why are B1 cells commonly the source of B-cell tumors, such as chronic lymphocytic leukemia (CLL)?
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Because of their ability for self-renewal
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What happens to the mature, naive B-cell after B-cell development is complete?
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It leaves the bone marrow and recirculates between the blood and secondary lymphoid tissues (lymph nodes, spleen, mucosa-associated lymphoid tissue, and lymph)
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Where do mature, naive B-cells encounter antigens?
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In the secondary lymphoid tissues (lymph nodes, spleen, mucosa-associated lymphoid tissue, and lymph)
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Where are antigen-specific B-cells held?
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In T-cell areas
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What activates antigen-specific B-cells?
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Antigen-specific CD4 T-helper cells
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a) In the lymph nodes and spleen, what do activated B-cells do?
b) The change in the processing of heavy chain mRNA leads to the synthesis of what form of Ig instead of the membrane-bound form? |
a) Proliferate and differentiate into antibody-secreting plasma cells.
b) Secreted form |
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What cells are specialized in the constitutive synthesis and secretion of antibody?
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Plasma cells
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T/F
Plasma cells' cellular organelles for protein synthesis are highly developed. |
True!
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What percent of the total protein from plasma cells is antibody?
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10-20%
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Plasma cells are terminally differentiated and cease to divide. They do not express cell-surface Ig or MHCII molecules.
Therefore, they (can/cannot) respond to antigen or interact with T-cells. |
Cannot
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How long is the life span for plasma cells?
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About 4 weeks
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