Kinetics of disease response in a patient with multiple myeloma following TK⁺ DLI. Patient 17 affected by IgA-secreting multiple myeloma was treated with a single infusion of TK⁺ DLI. Absolute numbers of circulating TK⁺ cells, quantified by FACS analysis, are shown as ■. Percentage of malignant cells in the bone marrow (black sectors of pies) was assessed by quantification of monoclonal plasma cells in the bone marrow. Disease status was also monitored by the levels of serum monoclonal IgA (▴) and confirmed by IgAκ immunofixation (not shown). Clearance of all parameters of disease closely followed the peak of circulating TK⁺ cells.