CD1a⁺ DCs obtained from leukapheresis of seven patients strongly stimulate allogenic T-lymphocyte proliferation. DCs were generated by 7 days of culture of ACs from 7 MM patients in the presence of GM-CSF and IL-4. These DCs were washed three times, irradiated at 30 Gy, and used in MLR reaction as stimulator cells for 1.5 × 10⁵ allogenic T cells from healthy volunteers. Cell proliferation was evaluated by a 12-hour pulse with ³H-TdR after 5-day cocultures. The MLR obtained with DCs from the patient with PCL (patient 9) is shown by the black histograms. Data are expressed as mean ± SD of sextuplet independent cultures. ³H-TdR incorporation rates of irradiated DCs or purified T cells were less than 600 cpm.