Aberrant IgL rearrangements in CXP lymphomas. (A, right) Southern blot analyses for Jκ rearrangements in CXP lymphoma genomic DNA using BamHI digestion and the 3′ Jκ and Cκ probes indicated in schematic at top of panel. (left) Southern blot analysis for RS rearrangements in CXP lymphoma DNA using BglII digestion and the indicated RS0.8 probe. Germline (GL) bands and their known sizes are indicated (arrows). Blots were performed at least two times. (B) Assays for rearrangements occurring in or near Vλ and Jλ segments in DNA samples from CXP lymphomas. Rearrangements were isolated either by PCR or by cloning from λ-phage genomic DNA libraries generated from individual tumor DNA samples. Black arrows denote the position of the PCR primers used for the studies, and primer sequences are indicated in the Materials and methods section. The two breakpoints for a given rearrangement in the vicinity of Vλ and Jλ in a particular tumor are indicated by the same number with the breakpoint in the Jλ region indicated by a (′) symbol. PCR analyses were performed at least three times from one or multiple independent DNA samples from a given tumor. PCR fragments were subcloned into the pGEM vector, and 10–20 subclones were sequenced. Identical rearrangements that were isolated from >80% of the subclones were scored as clonal rearrangements. At least two independent phage clones were isolated from each genomic library and the junctions found in phage clones were independently confirmed as clonal junctions in a given tumor by PCR analyses of tumor cell DNA. Sequences of cloned Vλ and Jλ rearrangement junctions are shown in Fig. S5E.