Term
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Definition
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Term
| what makes a good T cell? |
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Definition
| can interact with self-MHC molecules presenting peptides from pathogens. |
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Term
| what makes a bad t cell? why would you negatively select against their further maturation? |
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Definition
| interact with self-MHC molecules presenting with SELF-peptides. |
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Term
| what are the 2 flavors of T cells? |
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Definition
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Term
| what two cells of the thymus play an important role in T cell positive/negative selection? |
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Definition
| Cortical epithelial and medullary epithelial cells. |
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Term
| T/F: the thymus involved in lymphocyte recirculation. |
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Definition
| False. it doesnt receive lymphoid drainage either. |
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Term
| how long do T cells stay in circulation? |
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Definition
| YEARS!! they don't go away readily. |
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Term
| What happens in DiGeorge's Syndrome? |
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Definition
| No thymus; Thus no mature T cells = get sick easier. |
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Term
| how do cells get into and out of the thymus? |
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Definition
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Term
| what happens to an old thymus? |
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Definition
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Term
| what are the two subsets of T cell receptors? |
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Definition
| CD4+ and CD8+. As a reminder, when cells enter the thymus they are CD4- and CD8-, also called "double negative" |
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Term
| what are the four genes that can make up the T cell receptor? |
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Definition
| alpha, beta, gamma, delta. |
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Term
| which genes rearrange first? |
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Definition
| its a race between the Beta, Gamma and Delta chains. Most often, the Beta chain rearranges first! |
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Term
| what is a pre-T cell receptor? |
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Definition
| when the Beta chain binds to a surrogate alpha chain and it can bind to an unknown ligand. Currently a double negative (CD4-, CD8-) T cell. |
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Term
| when does the T cell proliferate and what happens to the CD4 and CD8 after proliferation? |
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Definition
| after the chain rearrangement stops. the CD4 and CD8 become positive. |
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Term
| After you get a CD4+ and CD8+ T cell, what happens next? |
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Definition
| alpha gamma and delta chain rearrangment race! the alpha usually wins, thus making its partner alpha:beta. |
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Term
| what do T cell receptors recognize? |
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Definition
| peptide attached to self-MHC (class 1or2) |
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Term
| in T cell positive/negative selection: what is compatibility testing? |
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Definition
| thymocytes (cortical epithelial cells) attempt to interact with self peptides and self-MHC molecules on the surface of the cortical epithelial cells. If it binds, a positive signal is sent to continue the maturation process. |
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Term
| What is HLA ? why is it important? |
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Definition
| Human Leukocyte Antigen. Recipients of bone marrow transplantation must allow for foreign bone marrow stem cells that create new T cells. |
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Term
| how much of a match is needed in HLA allotypes? Why "no good if no match" ? |
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Definition
| AT LEAST one in class I and one in class II. Key point, the antigen-presenting cells in the recipient are donor-derived. T cells selected for in the thymus cannot interact with antigen presented by donor HLA allotypes on donor-derived antigen-presenting cells. |
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Term
| what happens when a CD4+/CD8+ T cell encounters a Cortical epithelial cell and binds to the peptide/MHC-classI complex? |
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Definition
| it loses its CD+ and becomes only CD8+ |
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Term
| what happens when a CD4+/CD8+ T cell encounters a Cortical epithelial cell and binds to the peptide/MHC-classII complex? |
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Definition
| it loses its CD8+ and becomes only CD4+ |
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Term
| what is the Bare Lymphocyte syndrome? |
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Definition
| lack of expression of either MHC class I or II molecules by both: lymphocytes and thymic epithelial cells. Persons lacking Class I expression are only CD4+ |
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Term
| when is a T cell negatively selected? |
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Definition
| when it is a single positive (CD4+ or CD8+) and it interacts with a macrophage or bone marrow derived dendritic cell. |
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Term
| what determines whether or not the interaction between self peptide and self MHC and the T Cell Receptor results in positive or negative selection? |
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Definition
| the STRENGTH of the interaction. If it too tight, slected against. If it is weak binding, positive selection. |
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