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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.
Positive selection ensures that mature T cells can functionally recognize MHC molecules in the periphery (i.e. elsewhere in the body). The TCRs of T lymphocytes recognise only sequential epitopes , also called linear epitopes , of only peptides and only if coupled within an MHC molecule.
functional (beta selection) functional (positive selection) autoreactive (negative selection) location: cortex: cortex: cortex/medulla In order to pass the β-selection checkpoint, the β chain of the T cell receptor rearranged by the thymocyte must retain the structural properties allowing it to be presented on the surface of the thymocyte ...
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 ]
Therefore, positive selection of GC B cells in the light zone results in B cells that express antibodies with high affinity for the antigen. [3] The B cells that are positively selected in the light zone begin to express cMyc, which regulates the germinal center and the proliferation of the B cells in the germinal center. [3]
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 .
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.
Then the cell stops producing all other side chains and starts intensive synthesis and secretion of the antigen-binding side chain as a soluble antibody. Though distinct from clonal selection, Ehrlich's idea was a selection theory far more accurate than the instructive theories that dominated immunology in the next decades.