Sequence alignment demonstrating homology between IgVH3–15 and the heavy chain genes of MWCL-1 cells and the primary tumor. PCR-amplified DNA was prepared and sequenced as discussed in “Sequence analysis of IGHV.” The sequence was compared with germline configurations using IMGT/V-QUEST software Version 3.2.17 on the IMGT website (www.imgt.cines.fr/IMGT_vquest/share/textes). Identical V_H sequences were obtained for both MWCL-1 cells and the primary tumor, but this common sequence is only referred to as MWCL-1 in the figure.