Pretreatment with SLT-1 depletes malignant B-lymphoma cells, B-CLL, and B or plasma cells from myeloma patients. MNC derived from lymphoma biopsies or PBMC from B-CLL (top panel) or from myeloma blood or BM (bottom panel) were pretreated with 5 μg/mL of SLT-1 for 60 minutes, washed, and cultured for 6 to 11 days. Viable cells were then enumerated and analyzed using anti-CD19 MoAb to detect B cells and anti-CD38 MoAb to detect plasma cells, together with PI staining to identify live versus dead cells. The absolute number of B or plasma cells remaining in cultures was calculated as the percentage of viable CD19⁺ or CD38⁺ cells times the number of viable cells per culture. The numerical values indicate the extent of B-cell or plasma cell depletion by SLT-1 as compared with the untreated control cultures. Patient MMB3 was posttransplant and had no detectable clonotypic B cells before harvest of the blood sample used here (not shown).