Examples of Clonal selection in the following topics:
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- Clonal selection is an theory that attempts to explain why lymphocytes are able to respond to so many different types of antigens.
- Clonal selection assumes that lymphocytes are selected during antigen presentation because they already have receptors for that antigen.
- In clonal selection, an antigen is presented to many circulating naive B and (via MHC) T cells, and the lymphocytes that match the antigen are selected to form
both memory and effector clones of themselves.
- Clonal selection may also be used during negative selection during T cell maturation.
- Clonal selection is thought to cause mutations of antigen-binding affinity in memory cells during clonal expansion so that memory cells have greatly increased antigen-binding affinity than the effector cells during the first response.
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- B cells undergo clonal selection and develop similarly to T cells with some notable differences.
- This is a form of positive selection.
- B cells are also tested for autoreactivity through negative selection.
- Clonal selection is a theory stating that B cells express antigen-specific receptors before antigens are ever encountered in the body.
- Following the initial infection, random mutations during clonal selection could produce memory B cells that can more easily bind to antigens than can the original B cells.
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- Differentiation into helper T cell subtypes occurs during clonal selection following T cell activation of naive T cells.
- Their major role is to shut down T cell-mediated immunity toward the end of an immune reaction and suppress auto-reactive T cells that escaped the process of negative selection in the thymus.
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- Memory cells derive from their parent B and T cells, and undergo clonal selection following infection, which increases antigen-binding affinity.
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- As its functional mass shrinks by about 3% a year throughout middle age, there is a corresponding fall in the thymic production of naive T cells, leaving clonal expansion of immature T cells to play a greater role in protecting older subjects.
- Positive selection designates T cells capable of interacting with MHC.
- Double-positive cells (CD4+/CD8+) that are positively selected on MHC class II molecules will eventually become CD4+ helper T cells, while cells positively selected on MHC class I molecules mature into CD8+ cytotoxic T cells.
- The potentially autoimmune cells are removed by the process of negative selection.
- Negative selection removes thymocytes that are capable of strongly binding with self-antigens presented by MHC.
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- They have an immunosuppressive effect that inhibits cell-mediated immunity at the end of a response and destroys autoimmune T cells that aren't filtered out by negative selection in the thymus.
- While in the bone marrow, B cells are sorted through positive and negative selection in a manner somewhat similiar to T cell maturation in the thymus, with the same process of killing B cells that are nonreactive to antigens or reactive to self-antigens.
- Instead of apoptosis, though, defective B cells are killed through other mechanisms such as clonal deletion.
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- When the B cell fails in any step of the maturation process, it will die by a mechanism called apoptosis, or specifically, clonal deletion.
- Such clonality has important consequences because immunogenic memory relies on it.
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- During antigen presentation, such as from the dendritic cells, lymphocytes migrate to germinal centers of the secondary lymphoid tissues, where they undergo clonal expansion and affinity maturation.
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- the accumulation and the clonal expansion of memory and effector T-cells
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- Circulating antibodies are produced by clonal B cells that specifically respond to only one antigen.