Fig. 2.

Quantification of sjTRECs by competitive PCR. (a) Schematic representation of the localization of the two primer pairs used for quantification of sjTRECs, and of the cellular β-globin gene. (b) Competitor for competitive PCR amplification. Two long primers, corresponding to the SJ1/PCO3 and to the SJ2/PCO4 sequences, were used to amplify a DNA competitor corresponding to the β-globin PCO3-PCO4 amplification product and containing an additional 20 bp in its middle. Construction of this competitor has already been described [40]. The resulting DNA fragment contains primer recognition sequences for both the β-globin and sjTRECs primer pairs, and amplifies DNA segments of a different size to those obtained from the respective target DNA sequences. (c) Competitive PCR. For each quantification, DNA extracted from peripheral blood mononuclear cells was mixed to a different concentration of competitor (as indicated on top of each photograph) and amplified with the two primer pairs. According to the principles of competitive PCR, the ratio between amplification products for the competitor (C) and the target sjTRECS (T), or between the competitor and the target genomic DNA (G), accurately reflects the ratio of these species in the input reaction. The quantitative results obtained by the competitive PCR experiments shown in the two gels are indicated on the left side of each photograph. M: molecular weight markers.