Expression profile of Pax-5a, Pax-5/Δ-Ex8, Id-2, AID, and switch transcripts in CLL B cells before and after stimulation with CD40L+IL-4. (A) Purified B cells from CLL patients 01 and 28 were stimulated in vitro with CD40L+IL-4 molecules, and amplification of Pax-5, Pax-5/Δ-Ex8, Id-2, AID, and GAPDH was analyzed. Splicing variants of the AID gene described in a previous work²⁴  are labeled a, b, and c. (B) Quantification of Pax-5a (▪), Pax-5/Δ-Ex8 (▦), and Id-2 transcripts (□) before and after CD40L+IL-4 stimulation. All amplifications were normalized to GAPDH mRNA and the gene copy number was calculated. (C) CSR analysis by RT-PCR. Amplifications of purified B cells from activated and nonactivated CLL patients (nos. 01 and 28) using Ig isotype–specific primers are depicted.