Real time-PCR assay estimating the naive T-cell pool in whole blood and dried blood spot samples: pilot study in young adults.

Because of their central role orchestrating the immune response, the decrease in repertoire number and diversity of naïve T-cells is a significant feature of immnosenescence. Reflecting the effective naive T-cell pool, quantifying the sj-TREC ratio (number of signal joint T-cell receptor excision circles/10(5) T-cells) in blood samples suffers however from constraints. The most limiting one is the absolute requirement of the flow cytometry analysis of peripheral blood samples for the T-cell numeration. In order to make this ratio more accessible for clinical and epidemiological studies addressing how changes in responsiveness of the immune system lead to an increased susceptibility to various diseases and poorer response to vaccination, we have developed a rapid and simple method for the quantification of the sj-TREC ratio in whole blood and in dried blood spot (DBS) samples. This novel method is a QPCR analysis using fluorescently labelled sequence-specific probes both for quantifying sj-TREC and T-cell count and therefore eliminating the absolute necessity of the flow cytometer analysis. In this pilot study, we have compared the sj-TREC ratio we obtained with this novel method in whole blood and in DBS samples of 10 healthy volunteers with those obtained with the technique of reference and found that they are comparable.