Identical rearrangements of T-cell receptor genes in concordant twin T-cell malignancy. (A) Southern blot analysis of TCRβ rearrangements showing shared bi-allelic rearrangements (same sized restriction fragments). gl, germ line position. (B) PCR analysis of TCR and IGH gene rearrangements in the twin pair showing identical sized amplified bands for both TCRβ (TCRB) and TCRγ (TCRG) in the twin pair. Note twin 1 also has a weak clonal VDJ-IGH rearrangement that is absent in twin 2. It is not possible to say whether or not this clonal rearrangement was in the T-cell leukemic clone. bcl-2 primers were used as negative controls. M, markers. (C) Sequence comparison of cloned DJ-TCRβ amplicons showing identical N region (boxed).