Term
| Where does negative selection of B cells occur? |
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Definition
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Term
| Where does positive selection of B cells occur? |
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Definition
| secondary lymphoid tissue |
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Term
| Name the distinguishing CD marker of a pluripotent hematopoietic stem cell. |
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Definition
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Term
| Name the cells in the B cell lineage. |
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Definition
| pluripotent hematopoietic stem cell-> common lymphoid progenitor-> B cell precursor -> pro-B cell -> pre B cells -> B cell |
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Term
| What gene segments rearrange in early versus late pro-B cells? |
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Definition
| early- DH + JH rearrange; late- DJH + Vh |
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Term
| Do B cells rearrange their heavy or light chains first? |
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Definition
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Term
| When does a pro b cell become a pre b cell? |
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Definition
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Term
| In what stage of B cell development are IgMs first assembled? |
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Definition
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Term
| Where in the body does B cell gene rearrangement occur? |
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Definition
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Term
| Which comes first, large or small pre B cells? |
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Definition
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Term
| In what B cell type does VL-JL rearranging take place? |
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Definition
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Term
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Definition
| supportive cells and connective tissue in an organ |
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Term
| How do stromal cells in the bone marrow contribute to B cell development? |
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Definition
| they provide CAMS (cell adhesion molecules) and growth factors |
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Term
| T/F IL-7 is required for stimulation and proliferation of young B cells. |
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Definition
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Term
| What's the chance that a VDJ rearrangment will be correct? |
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Definition
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Term
| DJ rearrangement occurs in which B cells? |
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Definition
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Term
| VDJ rearrangement occurs in which type of B cell? |
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Definition
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Term
| In which cell is VJ for the light chain rearranged? |
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Definition
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Term
| What is the Ig status of a large pre B cell? |
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Definition
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Term
| What is the Ig status of a small pre B cell? |
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Definition
| u chain is made in the endoplasmic reticulum |
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Term
| What is the Ig status of an immature B cell |
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Definition
| u heavy chain, lamdba or K light chain, IgM on surface |
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Term
| How is it possible that so many VDJ arrangments are productive when they are so randomly spliced? |
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Definition
| there are DNA modifying enzymes and transcription factors that fine tune B cell development. People with genetic defects in these manifest as immunodeficient |
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Term
| What is allelic exclusion in the context of heavy chain formation? |
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Definition
| DJ is rearranged on both chromosomes and then triggers rearrangment of VDJ first on one chromosome then another. Allelic exclusion is when there is a successful VDJ arrangment on one chromosome that stops the VDJ rearrangment on the second chromosome |
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Term
| T/F If the DJ rearrangement is unsuccessful, the B cell with undergo apoptosis before it has chance to make a B cell. |
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Definition
| FALSE, if the VDJ rearrangment is unsuccessful the B cell ALWAYS undergos apoptosis AFTER VDJ is made |
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Term
| What are surrogate light chains? |
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Definition
| proteins that mimic light chains and can combine to heavy chains. This makes sure that pro B cell has made a heavy chain able to combine with an Ig light chain |
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Term
| Which genes encode the surrogate light chain? |
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Definition
| VpreB encodes the variable region and "lambda"5 encodes the contant region (controlled by E2A and EBF |
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Term
| What is the pre B cell receptor? |
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Definition
| u chains that assemble with surrogate light chain and other factors. Successful assembly stops signal for heavy chain rearrangment |
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Term
| How does the pre B cell stop heavy chain rearrangment from occuring? |
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Definition
| stops transcription of RAG genes, degrades RAG proteins, and reorganizes chromatin structure |
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Term
| Why is it adventageous for a B cell to exhibit allelic exclusion and have all of its immunoglobulins identical? |
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Definition
| binds with antigens with high avidity |
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Term
| How do some B cells have identical heavy chains but different light chains? coincidence? |
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Definition
| pre B cells go through rounds of division before RAG genes are turned back on and light chain is rearranged |
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Term
| What series of steps must occur for a light chain rearrangment to be unsuccessful and cause apoptosis? |
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Definition
| kappa gene on first chromosome unsuccessful -> kappa gene on second chromosome unsuccessful -> lambda on first unsuccessful -> lambda gene on second unsuccessful -> apoptosis |
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Term
| Why is it adventageous to have genes for both kappa and lambda when they are functionally identical? |
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Definition
| increases sucess rate of rearranging a good light chain to 85% |
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Term
| T/F One gene for heavy chain can be rearranged multiple times until a succesful chain is made. |
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Definition
| FALSE, this only happens in light chains |
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Term
| What halts light chain rearrangment once a successful light chain has been made? |
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Definition
| light chain assembles with u to form igM and then assembles with cofactors to form the B cell receptor. B cell receptor is transported to cell surface and halts further gene rearrangement |
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Term
| What must a B cell have to "pass" the two "checkpoints"? |
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Definition
| successful heavy chain/pre B cell receptor and successful light chain/B cell receptor |
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Term
| What is x linked agammaglobulinemia? |
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Definition
| pts lack a functional Bruton's tyrosine kinase (Btk) gene so there are no circulating B cells and no Ab. Immune deficiency against extracellular and pyogenic pathogens |
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Term
| Tonsils are mostly made up of... |
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Definition
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Term
| How do B cell translocations cause cancer? |
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Definition
| protooncogene is translocated accidentally to Ig gene and transcribed becoming an oncogene |
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Term
| What causes Burkitt's lymphoma? |
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Definition
| Myc gene (which regulates the cell cycle) switches places with the Ig gene |
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Term
| Name the only B cell that expresses CD 5. |
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Definition
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Term
| Why do B-1 cells have restricted antigenic repertoires? |
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Definition
| they are produced prenatally when TdT is not expressed. Therefore no N nucleotides and less diversity |
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Term
| On what cell would you find low affinity, poly reactive antibodies that bind to carbohydrate antigens? |
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Definition
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Term
| What keeps up the B-1 cell population once the bone marrow stops making them? |
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Definition
| they self renew or divide |
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Term
| What causes most cases of chronic lymphocytic leukemia? |
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Definition
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Term
| Why are other B cells monospecific while B-1 cells are polyspecific? |
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Definition
| B cells need to have high affinity for when they undergo clonal expansion |
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Term
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Definition
| when B cells do not react with self antigen |
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Term
| When do B cells finally begin to express IgM and IgD? |
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Definition
| when they enter the blood stream there is alternative mRNA splicing that allows expression of IgM and IgD |
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Term
| What happens to B cells that bind a self antigen in the bone marrow? |
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Definition
| can undergo further light chain rearrangement. surface IgM is reduced and RAG expression continues |
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Term
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Definition
| when a B cell keeps recognizing self antigens until no more light chain rearrangements are possible and cell undergoes apoptosis |
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Term
| What does univalent mean? |
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Definition
| there is only one epitope |
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Term
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Definition
| when a B cell can bind to univalent self antigen. B cell makes the nonfunctional IgM receptor so it is not activated when it binds to self antigen in peripheral circulation. Cell dies in 1-5 days |
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Term
| What is the normal half life of mature B cells? |
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Definition
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Term
| Where is central tolerance of B cells achieved? |
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Definition
| primary lymphoid organ--bone marrow |
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Term
| What is peripheral tolerance? |
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Definition
| Tolerance induced outside of primary lymphoid organ (bone marrow). Circulating B cells taht encounter self antigen soon after hitting perphery are rendered anergic or die via apoptosis |
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Term
| When is an immature B cell said to be mature? |
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Definition
| when it enters secondary lymphoid tissue |
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Term
| B cell survival in the periphery depends on... |
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Definition
| regular passage through primary follicles of 2ndary lymphoid tissue. IF they meet antigen they are detained in the T cell area and signaled to proliferate and differentiate |
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Term
| After a primary immune response subsides, memory b cells are made from... |
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Definition
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Term
| Hodgkin's lymphoma is due to uncontrolled growth of... |
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Definition
| germinal center B cell in the periphery |
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Term
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Definition
| uncontrolled growth of plasma cells in the bone marrow that secrete monoclonal immunoglobulin. Cause tumors in bone that enlarge and cause erosions in the bone. |
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Term
| What happens if a naive B cell doesn't encounter an antigen? |
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Definition
| it dies quickly (within weeks) |
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Term
| T/F Plasma cells both secrete and express surface Ig. |
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Definition
| FALSE, they only secrete it |
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Term
| T/F Plasma cells both secrete and express surface Ig. |
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Definition
| FALSE, they only secrete it |
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Term
| T/F Plasma cells both secrete and express surface Ig. |
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Definition
| FALSE, they only secrete it |
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