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19 Cards in this Set
- Front
- Back
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What are the four important events in the development of B and T lymphocytes?
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1) Commitment of progenitor cells
2) Rearrangement of antigen receptor genes 3) Selection of cells that have produced correct antigen receptor proteins/elimination of others 4) Differentiation of B and T lymphocytes (ex: CD4+ vs. CD8+) |
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What do hematopoietic stem cells mature into in lymphocyte development?
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Common lymphoid progenitors (CLPs)
*Found in the fetal liver and adult bone marrow |
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Which cytokine stimulates the proliferation of common lymphoid progenitors?
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IL-7
*Proliferation precedes antigen receptor rearrangement *Mutations in IL-7 receptor -> SCID |
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What is the earliest bone marrow cell committen to the B cell lineage?
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Pro B cell
*Do not express Ig |
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Protein products of what genes mediate Pro B cell recombination?
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RAG-1 and RAG-2
*D-J then V-DJ |
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What marks the transition from the Pro-B to the Pre-B stage of differentiation?
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Synthesis of the u heavy chain and halting of the second locus
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What is the Large pre-B cell receptor complexed with?
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u (heavy chain) is complexed with a Surrogate Light Chain
*This checks for pre-B cell receptor expression |
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If a Pre-B cell receptor is expressed, what occurs next?
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1) Pre-B cell receptor halts rearrangement of the other heavy chain locus
2) Large pre-B cells -> small pre-B cells |
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Why do most Igs in the body contain k light chains?
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Rearrangement of k chain is attempted first
*If both k chains fail, then gamma chain genes are rearranged |
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What type of antigens do immature B cells interact with?
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Self-antigen!
*Cell is either deleted, inactivated, or edited |
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What Immonoglobulins do mature B cells co-express?
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IgM and IgD
*Occurs by alternate splicing |
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What are the two main differences in the development of T and B cells?
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1) T cells must emigrate from the bone marrow to thymus
2) Developing T cells must undergo positive selection (ensures receptor can recognize Class I or II MHC) |
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In what stage of T cell differeentiation do the cells enter the thymus?
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Stem cell stage
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What marks the transition from pro-T cells to pre-T cells?
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Successful rearrangement of the TCR B chain
*B chain expressed at cell surface complexed w/ pre-Ta (pre-T cell receptor) |
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What stimulates the rearrangement of the a chain in T cell differentiation?
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Successful expression of pre-T cell receptor (B chain + pre-Ta)
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In what stage of T cell differentiation does postivie and negative selection occur?
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Double positive thymocytes
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If a double positive thymocyte sees class 1 MHC, what does it make?
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Only CD8+ (single positive)
*If sees MHC II, makes only CD4+ |
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What is meant by T-cell negative selection?
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a/b TCR T cel binds self peptide antigen and MHC very tightly, suggesting cells are self-reactive and could mediate autoimmune reactions. Cells are deleted via apoptosis or rendered anergic
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Do B cells undergo positive rearrangement?
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NO. They have no requirement for MHC complex
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