Positive and Negative Selection of T Lymphocytes
This extract was created in the absence of an abstract.
Excerpt
Precursors of functional T lymphocytes originate in the bone marrow and migrate to the thymus to undergo the necessary developmental events that result in functional T cells. Once within the thymus, genes encoding the antigen-specific T-cell receptor (TCR) undergo somatic DNA rearrangements in a highly regulated manner. The resulting cell-surface TCR allows the differentiating thymocytes to interact with the products of the polymorphic major histocompatibility complex (MHC) displayed in the thymus, allowing “thymic education” to take place. The end result of this process is the presence in the periphery of a TCR repertoire that is skewed toward recognition of antigens in the context of self-MHC molecules (MHC restriction), as well as elimination of T cells that react “too strongly” with self-MHC (self-tolerance). In addition, surface expression of the CD4 or CD8 molecule divides peripheral T cells into mutually exclusive subsets correlating strictly with the nature of the restricting MHC molecules....
