Igμ/BCL6 translocation products from human primary B cells. (A) Sensitivity of the genomic DNA PCR assay for Igμ/BCL6 translocation. Various DLBCL cells known to have Igμ/BCL6 translocation were diluted into the background of DG75 cells as DNA template for PCR, and the sensitivity of the assay was determined to be between 3 and 10 copies/reaction. (B) Diagram of the primer position for the PCR. (C) PCR amplification of the Igμ/BCL6 translocation products from CD38⁺ B cells from spleen (S3) and tonsils (T14 and T16). (D) Recombination breakpoints of the 3 isolated translocation products are shown. The lowercase letters present the sequences from Ig Sμ; and the capital letters, for the intron 1 sequence of the BCL6 gene. The overlapped nucleotides in the breakpoints are underlined. The internal deleted portion of the Sμ in the clone T14 is indicated with the dashed line. The sequence numbers correspond to the BCL6 gene of GenBank accession no. AY189709. The breakpoint positions for these clones are diagrammed in Figure 1.