The analysis of human Ig-V H sequences was performed as follows. Total RNA was isolated from approximately 5610 5 monoclonal B cells with Trizol (Invitrogen). The cDNA was generated and subjected to PCR with primers specific to the different V H family members. PCR products were sequenced to determine the CDR3 region of the different clones. Sequence analysis was performed using BigDye Terminator chemistry (Applied Biosystems Inc.) and CodonCode Aligner software.