Valuing Diversity

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Science  01 Jan 1999:
Vol. 283, Issue 5398, pp. 8
DOI: 10.1126/science.283.5398.8e

Developing CD4 T cells (thymocytes) are equipped with T cell antigen receptors (TCRs) specific to each T cell, but there is an enormous diversity of specificities over the population of thymocytes. How do the “right” T cells get selected to mature fully? Barton and Rudensky (p. 67) evaluated mice that were engineered to have 95% of their thymocytes expressing the same peptide for binding to the major histocompatibility complex (MHC). These mice had normal numbers of mature CD4 T cells, so it appeared that a single peptide could select millions of T cells. However, if the 5% of peptides that were different from the major peptide-MHC complex were not present, the number of mature CD4 T cells dropped. Thus, a diversity of low-abundance peptides is necessary to get a normal population of mature CD4 T cells.

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