CMRF44+dendritic cells from peripheral blood stem cell harvests of patients with myeloma as potential cellular vectors for idiotype vaccination

The optimal conditions required to harvest dendritic cells (DC) for immunotherapy were investigated in a series of preliminary investigations using peripheral blood stem cell (PBSC) harvests and blood from patients with myeloma. There was no difference in the number of DC (CMRF44+, CD19-, CD14-) in PBSC mobilized with G-CSF (mean 0.28%, n =7 ) compared with GM-CSF (mean 0.24%, n =6 ) and apheresis itself did not concentrate DC. In longitudinal studies ( n =10), the peak DC count (day 12 post PBSC harvest) did not correlate with the peak CD34+ cell count or white cell count. A simple affinity purification of DC resulted in a mean 63-fold purification. Affinity enriched suspensions from normal blood contained more DC (mean=18.8%; n =5 ) than those from patients with myeloma (mean=9.9%; n =13 ). The percentage of DC with a lymphoid phenotype (CD11c-, CDw123(hi) +) was significantly higher in G-CSF mobilized PBSC harvests (22.7%; n =6 ) than in peripheral blood samples from patients with myeloma (7.0%; n =13; p =0.01 ). DC endocytosis was normal and did not change throughout the course of the disease. Neither DC numbers nor subsets changed significantly between days 1 and 3 of culture. Current mobilization procedures, optimized for PBSC, need to be altered when harvesting DC.