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Science 29 October 1999:
Vol. 286. no. 5441, p. 869
DOI: 10.1126/science.286.5441.869h
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This Week in Science

How many different T cell receptors (TCRs) are circulating on T lymphocytes in human blood? Because of the way that the TCR is constructed, the potential diversity is 1015. Not all T cells make it into the circulation, however, so measuring the real number has been extremely difficult. Arstila et al. (p. 958) have now measured a fraction of the repertoire and were able to estimate the actual extent of the diversity. They came up with a minimum number of 2.5 ¥ 107 different T cells. Memory T cells constitute only about 1 ¥ 105 to 2 ¥ 105 different clones, albeit some of these clones make up a large percentage of the total number of cells in circulation.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)