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The selection hypothesis argues that instead of being an intrinsic property, MHC restriction is imposed on the T cells during positive thymic selection after random TCRs are produced. [17] According to this model, T cells are capable of recognizing a variety of peptide epitopes independent of MHC molecules before undergoing thymic selection.
This selection process is vitally important in shaping the population of thymocytes into a peripheral pool of T cells that are able to respond to foreign pathogens but remain tolerant towards the body's own antigens. Positive selection selects cells which are able to bind MHC class I or II molecules with at least a weak affinity. This ...
In immunology, central tolerance (also known as negative selection) is the process of eliminating any developing T or B lymphocytes that are autoreactive, i.e. reactive to the body itself. [1] Through elimination of autoreactive lymphocytes, tolerance ensures that the immune system does not attack self peptides . [ 2 ]
B cells undergo two types of selection while developing in the bone marrow to ensure proper development, both involving B cell receptors (BCR) on the surface of the cell. Positive selection occurs through antigen-independent signalling involving both the pre-BCR and the BCR.
While cTECs control the functionality of TCRs during the process called positive selection, Medullary thymic epithelial cells (mTECs) that home in the inner part of the thymus- medulla, present on their MHC molecules self-peptides, generated mostly by protein Autoimmune regulator, to eliminate T cells with self-reactive TCRs via processes of ...
Following selection, each T lymphocyte shows dual specificity: The TCR recognizes self MHC, but only non-self antigens. MHC restriction occurs during lymphocyte development in the thymus through a process known as positive selection. T cells that do not receive a positive survival signal — mediated mainly by thymic epithelial cells presenting ...
A figure depicting the process of T cell / thymocyte positive and negative selection in the thymus. mTEC shown in orange. Medullary thymic epithelial cells (mTECs) represent a unique stromal cell population of the thymus which plays an essential role in the establishment of central tolerance.
In immunology, affinity maturation is the process by which T FH cell-activated B cells produce antibodies with increased affinity for antigen during the course of an immune response. With repeated exposures to the same antigen, a host will produce antibodies of successively greater affinities .