Intriguing sequence similarities between different high-level subsets. VH CDR3 sequences grouped to subsets 2 and 169 share molecular characteristics: a VH CDR3 composed of 9 aa and an aspartic acid (D) residue at position 107. Furthermore, the IGHV3-48 gene (utilized by all 169 rearrangements), is highly similar to the IGHV3-21 gene. The height of symbols within the stack indicates the relative frequency of each amino acid at that position. Amino acid position is according to the IMGT numbering for the V domain.²⁷