[Estimate of Recent Thymic Output Function - Quantification of T Cell Receptor Rearrangement Excision Circles (TRECs)].

For a long time, thymic function could not be monitored, as a consequence of the absence of adequate technology to detect recent thymic emigrants from naive T cells. T cell differentiation in the thymus is characterized by T cell receptor (TCR) rearrangement. During the rearrangement of TCRalpha gene segments, the deltaRec and psiJalpha rearrange to each other to delete the TCRdelta gene and form an extrachromosomal DNA circles, referred to as signal joint T cell receptor excision DNA circles (sjTRECs) or TRECs. TRECs are assumed to have a high stability, they can not multiply and consequently are diluted during T cell proliferation. It was recently suggested that quantitative detection of TRECs would allow for direct measurement of thymic output. In this review TRECs quantification is a powerful method to evaluate the thymic output function in both health and disease, including hematopoietic stem cell transplantation, hematopoietic malignancies, HIV infection and autoimmune disease, and so on is described.