• dendritic cells;
  • CD14+ cells;
  • multiple myeloma;
  • cellular immunotherapy

Summary. Circulating monocytes from multiple myeloma patients enrolled in a clinical study of anti-idiotype vaccination were labelled with clinical-grade anti-CD14 microbeads and positively selected with the CliniMACS instrument. Cells were then grown, according to good manufacturing practice guidelines, in fetal-calf-serum-free medium in cell culture bags and differentiated to dendritic cells (DC) with granulocyte–macrophage colony stimulating factor plus interleukin 4 (IL-4), followed by either tumour necrosis factor-α (TNF-α) or a cocktail of IL-1β, IL-6, TNF-α and prostaglandin-E2. The CD14+ cell yield was increased from 17·6 ± 6·5% to 93·8 ± 6·3% (recovery 64·4 ± 15·4%, viability > 97%). After cell culture, phenotypic analysis showed that 86·7 ± 6·8% of the cells were DC: 2·27 ± 0·9 × 108 DC/leukapheresis were obtained, which represented 20·7 ± 4·6% of the initial number of CD14+ cells. Notably, the cytokine cocktail induced a significantly higher percentage and yield (28·6 ± 3% of initial CD14+ cells) of DC than TNF-α alone, with secretion of larger amounts of IL-12, potent stimulatory activity on allogeneic T cells and efficient presentation of tumour idiotype to autologous T cells. Storage in liquid nitrogen did not modify the phenotype or functional characteristics of preloaded DC. The recovery of thawed, viable DC was 78 ± 10%. Finally, interferon-α-2b was at least as efficient as IL-4 in inducing the differentiation of mature, functional DC from monocytes.