RT-PCR detection of the ΔCD20-spliced mRNA. Qualitative full-length RT-PCR (flCD20-PCR) and specific RT-PCR (ΔCD20-PCR) allowing detection, respectively, of both wt/Δ or specific Δ forms of CD20. cRaf PCR amplified a control gene. flCD20 and ΔCD20 controls consisted of plasmids carrying the respective cloned sequences (A) on different B- and T-cell lines and (B) on in vitro B-EBV–produced cell lines and their respective PBMCs and on CD19⁺- or CD20⁺-purified cells from healthy donors and their corresponding PBMCs.