Sequence alignment of the expressed variable light chainregion (VL) and variable heavy chainregion (VH), using DNAplot software in VBASE. (a) Sequences of expressed Vλ regions compared with gene 2a2. (b) Sequences of expressed VH regions compared with genes 1-03 (IS4) and 3–23 (B3). The DH regions could not be matched to germline genes. Arginine residues altered by site-directed mutagenesis to serine residues in IS4VH complementarity determining region (CDR) 3 are underlined. Amino acids are numbered according to Kabat. Dots inserted to facilitate the alignment. Dashes indicate homology with the corresponding germline sequence. FR, framework region.