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The FOXP3 + subset of human CD4 + CD8 + thymocytes is immature and subject to intrathymic selection
Author(s) -
Tuovinen Heli,
Pekkarinen Pirkka T,
Rossi Laura H,
Mattila Ilkka,
Arstila T Petteri
Publication year - 2008
Publication title -
immunology and cell biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.999
H-Index - 104
eISSN - 1440-1711
pISSN - 0818-9641
DOI - 10.1038/icb.2008.36
Subject(s) - foxp3 , thymocyte , cd8 , biology , interleukin 7 receptor , population , cytotoxic t cell , microbiology and biotechnology , t cell , downregulation and upregulation , immunology , antigen , il 2 receptor , genetics , immune system , gene , in vitro , medicine , environmental health
FOXP3, believed to be the regulatory T (Treg)‐cell determining factor, is already expressed at the CD4 + CD8 + thymocyte stage, but there is disagreement whether these cells are the precursors of mature CD4 + CD8 − Treg cells. Here, we provide a quantitative analysis of FOXP3 expression in the human thymus. We show that a subset of CD4 + CD8 + cells already expressed as much FOXP3 as the FOXP3 + CD4 + CD8 − cells, and like mature Treg cells were CD127 low . In contrast to earlier data, CD8 + CD4 − thymocytes expressed significantly lower levels of FOXP3 than either the CD4 + CD8 + or CD4 + CD8 − subsets. The CD4 + CD8 + double‐positive cells also expressed recombination‐activating gene‐2, suggesting that they were still immature. Although the FOXP3 + double‐positive cells are thus putatively the precursors of the mature CD4 + CD8 − FOXP3 + subset, their frequency did not predict the frequency of more mature Treg cells, and analysis of T‐cell antigen receptor repertoire showed clear differences between the two subsets. Although these data do not rule out an independent CD4 + CD8 + Treg cell subset, they are consistent with a model of human Treg cell development in which the upregulation of FOXP3 is an early event, but the first FOXP3 + population is still immature and subject to further selection. The upregulation of FOXP3 may thus not be the final determining factor in the commitment of human thymocytes to the Treg cell lineage.