Amino acid and nucleotide sequences of the CDR3 of virtually identical Ig heavy chains expressed by unrelated CLL patients. Alignments of the amino acid (A) and nucleotide (B) sequences of the CDR3 of the fifteen 51p1-encoded heavy chains are shown, compared with CLL sample A (CLL-A). Dots indicate homology at that position. Listed on the left margin is the designation for each CLL sample. Labels above indicate the relative positions of FW3, CDR3, and FW4. The sequences of the CDR3 of the SMI heavy chain and the germ-line sequences of the D3-16 and J_H3 genes are included at the bottom for reference.