Term
| What are the primary and secondary lymphoid organs? |
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Definition
Primary (sites of development)
-Bone marrow and thymus
Secondary (sites of antigen exposure)
-Spleen, lymph nodes, MALT |
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Term
| What is the B cell cell progression and any notable markers for each stage? |
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Definition
Lymphoid stem cell---->
Pro-B cell (PROgenitor) (Tdt)----->
Pre-B cell (Tdt [ends] & cytoplasmic μ chains)---->
Immature B cell (surface IgM)---->
Mature B cell (surface IgM & IgD)---->
Activated B cell---->
Plasma or memory cell |
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Term
| During which stage of B cell development do we have heavy chain gene rearrangement? |
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Definition
-During the pro-B cell stage
-Tdt and rag expression is also going on
-This stage ends and the next begins when we have completed μ heavy chains in the cytoplasm, marking the end of heavy chain rearrangement (and the usefulness of Tdt) |
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Term
| During which stage of B cell development do we have light chain gene arrangement? |
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Definition
-During the pre-B cell stage
-We will have cytoplasmic μ chains during this stage (awaiting the completion of the light chains)
-Tdt and rag gene expression both end during this stage (rag we will use for this stage, Tdt is not used) |
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Term
| What do the rag genes code for and when are they expressed in B cell development? |
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Definition
-They code for recombinases
-They are expressed during both chain rearrangements (i.e. during pro and pre-B cell stages) |
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Term
| When will B cells be Tdt+? |
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Definition
| -During pro and some of pre-B cell stages |
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Term
| What units comprise MHC class 1 receptors? What isotypes are expressed and how? In what cells do we find MHC class 1s? |
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Definition
-They have an α heavy chain and a β light chain
-The β chain is called β2-microglobulin. It is not expressed from the MHC gene region and functions in transport of class 1 antigen to the cell surface (loading the MHC 1, in other words)
-Cells express two each of HLA-A, B, and C (human leukocyte antigens) which make up the α chain
-The expression of the HLA regions is codominant with all six (two from each parent) being expressed
-The variability in HLA genes among the population is the primary cause of organ rejection
-We find MHC class 1 receptors on all nucleated cells plus platelets |
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Term
| What units comprise MHC class 2 receptors? What isotypes are expressed and how? In what cells do we find MHC class 2s? |
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Definition
-They have an α and a β chain of similar length which are both expressed within the MHC gene domain
-It has HLA-DP, DQ, & DR types which are expressed codominantly with two of each for 6 total types
-These six types are expressed in antigen presenting cells (APCs) |
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Term
| How do T-cells decide on whether to be CTLs or Th cells? |
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Definition
-If they bind better to class MHC class 1 (all cells) then they stop expressing CD4 and become CD8+ CTLs
-The opposite for MHC class 2 and Th cells |
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Term
| In terms of where the T cell is in the body, what is the progression and what are the notable markers? |
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Definition
Prethymic (Tdt only)---->
Thymic cortex (rag expression, CD4 & CD8+)---->
-This is where the chains are made and the only region of rag expression. Tdt stops after here too (functions in both chain's production for TCRs)
Thymic medulla (CD8 or CD4, no more Tdt)
Circulation (same as medulla) |
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Term
| Where do we see double positive T cells? |
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Definition
-Only in the thymic cortex (area of positive selection)
-We also see rag gene production here, and here only |
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Term
| Where would we see Tdt+, CD3-, CD4-, and CD8-? |
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Definition
-Prethymic T cells
-All three of the notable CDs are not produced until the cortex where the TCR is also produced |
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Term
| How do the T cells go into negative selection? Where? |
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Definition
| -They have passed positive selection and go to the medulla for negative selection as single positive cells (CD8 or CD4) |
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Term
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Definition
-A transcription factor expressed in the thymic medulla that causes a wide variety of self antigens to be expressed on cells
-It essentially controls the process of negative selection |
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