Beta-selection: abundance of TCRbeta-/gammadelta- CD44- CD25- (DN4) cells in the foetal thymus.
Hager-Theodorides, Ariadne L;
Rowbotham, Nicola J;
Outram, Susan V;
Dessens, Johannes T;
Crompton, Tessa;
(2007)
Beta-selection: abundance of TCRbeta-/gammadelta- CD44- CD25- (DN4) cells in the foetal thymus.
European journal of immunology, 37 (2).
pp. 487-500.
ISSN 0014-2980
DOI: https://doi.org/10.1002/eji.200636503
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Expression of TCRbeta and pre-TCR signalling are essential for differentiation of CD4- CD8- double negative (DN) thymocytes to the CD4+ CD8+ double-positive (DP) stage. Thymocyte development in adult Rag1, Rag2 or TCRbetadelta-deficient mice is arrested at the DN3 stage leading to the assumption that pre-TCR signalling and beta-selection occur at, and are obligatory for, the transition from DN3 to DN4. We show that the majority of DN3 and DN4 cells that differentiate during early embryogenesis in wild-type mice do not express intracellular (ic) TCRbeta/gammadelta. These foetal icTCRbeta-/gammadelta- DN4 cells were T lineage as determined by expression of Thy1 and icCD3 and TCRbeta DJ rearrangement. In addition, in the foetal Rag1-/- thymus, a normal percentage of DN4 cells were present. In wild-type mice after hydrocortisone-induced synchronisation of differentiation, the majority of DN4 cells that first emerged did not express icTCRbeta/gammadelta, showing that adult thymocytes can also differentiate to the DN4 stage independently of pre-TCR signalling. Pre-TCR signalling induced expansion in the DN4 population, but lack of TCRbeta/gammadelta expression did not immediately induce apoptosis. Our data demonstrate in vivo differentiation from DN3 to DN4 cell in the absence of TCRbeta/gammadelta expression in the foetal thymus, and after hydrocortisone treatment of adult mice.