Ig/TCR gene rearrangement stability patterns in 87 precursor-B–ALL patients subjected to comparative heteroduplex PCR analysis at diagnosis and at relapse.

Black squares represent monoclonal rearrangements; gray squares, biclonal/oligoclonal rearrangements; white squares, oligoclonal/polyclonal rearrangements detectable as weak Southern blot bands. All squares above the upper line represent stable MRD-PCR targets, while all squares below the lower line represent Ig/TCR gene rearrangements lost owing to clonal evolution. VH squares between the 2 lines have common DH-JH stems shared by different IGH rearrangements at diagnosis and at relapse. (A) Thirty-five patients with all PCR-MRD targets identified at diagnosis preserved at relapse; (B) 36 cases with some targets (ranging from one target to half of the targets) lost during disease course; (C) 16 patients with most or all clonal markers absent at relapse. Patient 4790 was not included in our evaluation of MRD-PCR target stability because the detected IGH andTCRG gene rearrangements at diagnosis were oligoclonal.VH indicates VH-JH gene rearrangements;DH, DH-JH gene rearrangements; Vκ, Vκ-Kde gene rearrangements; iκ,intronRSS-Kde gene rearrangements; Vγ, Vγ-Jγ gene rearrangements;Vδ, Vδ2-Dδ3 gene rearrangements; Dδ, Dδ2-Dδ3 gene rearrangements.