SLT-1 pretreatment depletes myeloma plasma cells by more than 3 log units as measured using a cellular limiting dilution RT-PCR analysis for clonotypic transcripts. Harvested cells from sample in Fig5 were further analyzed for the presence of clonotypic cells to enumerate specifically the depletion of the malignant clone. For myeloma patient no. 4, untreated or SLT-1–pretreated cultures were harvested at day 6 and deposited at limiting dilution into PCR tubes containing lysis buffer, followed by RT-PCR analysis using patient-specific primers as described in the methods section.24 The product amplified from cells of the control cultures was a clonotypic IgH VDJ transcript of the expected size and sequence. Products amplified from cells that were pretreated with SLT-1 were of an incorrect size and did not have an Ig sequence.