Some B-CLL samples express the AID full-length transcript and its splice variants. (A) Map of the PCR primers used showing their relative position on the AID mRNA sequence (GenBank no. AB040431). Exons are indicated by boxes and noncoding regions by lines. (B) Representative RT-PCR results from purified B cells from healthy individuals of similar age and a series of B-CLL cases. Each vertical lane represents one patient or subject. Full coding sequence using primer pair 63F and 1137R (upper panel). First 3 exons using primer pair 63F and 415R (middle panel). β-actin (lower panel). (C) The region between exon 3 and exon 5 contains multiple variants. PCR products from CLL332 using the primer pair 392F and 676R were run on a 2% agarose gel (left). The total PCR product was cloned, and individual clones representing each band were sequenced using M13 primers. The sequences are diagrammed at right. From the bottom: variant missing exon 4 (205 bp), variant lacking the first 30 bp of exon 4 (290 bp), full-length transcript (320 bp), variant retaining the intron 4 sequence (614 bp), variant containing intron 4 and intron 5 (1084 bp). The last variant is identical to the genomic sequence of AID and most likely arose from genomic DNA contaminating the RNA used for the RT-PCR.