Quantification of Recent Thymic Emigrants: T-Cell-Receptor Excision Circles

Abstract

In chickens, blood lymphocytes may be identified as recent thymic emigrants (RTEs) by the use of antibodies that react with the cell surface marker chT1. PCR quantification of T-cell receptor (TCR) rearrangement excision circles (TRECs) derived from TCR β chain locus rearrangement has been described and has been used to provide additional evidence that the differentiation of T cells with a diverse TCR repertoire continues until late adulthood. The quantitation of TRECs may be performed with unsorted cells or with subpopulations of cells purified by fluorescent cell sorting, magnetic bead separation, panning, or other techniques. In view of its high yield and relative simplicity, magnetic cell sorting with CD4 and CD8 microbeads and positive selection columns is often used. High TREC concentrations have been associated with changes in T-cell populations after the transplantation of thymic tissue in patients with DiGeorge syndrome and, in some cases, after highly active antiretroviral therapy (HAART) for human immunodeficiency virus (HIV) infection. Moreover, recent data suggest that TREC values may prove to be a useful predictor of disease progression for HIV infection.