CD34+-derived CD11c+++ BDCA-1++ CD123++ DC: expansion of a phenotypically undescribed myeloid DC1 population for use in adoptive immunotherapy

BackgroundDC are commonly defined as HLA-DR+/Lin− cells that can be CD11c+++ CD123+/−, termed DC1/myeloid DC that induce a Th1 response, or CD11c− CD123+++, termed DC2/lymphoid DC that induce a Th2 response. However, significant heterogeneity within DC preparations is apparent and supports the existence of several distinct DC subpopulations. This study aimed to expand and characterize CD34+ DC for use in immunotherapy.MethodsCD34+ cells were seeded at 1 × 105/mL and expanded for 14 days in RPMI + 10% autologous plasma supplemented with GM-CSF, IL-4, Flt-3L and SCF. Maturation was induced with TNF-α and PGE2 for 2 days. DC were analyzed morphologically, phenotypically with a panel of MAb to lineage and DC markers, and functionally in MLR, T-cell assays and T-cell cytokine secretion by ELISA.ResultsSignificant cellular expansion was observed: 60 ± 5 × 106 DC from 1 × 106 CD34+ cells (n=28). Phenotypically DC were characterized as HLA-DR++, CD11c+++, CD80++, CD83+, CD86++, CD123++, CD15++, CD33++, BDCA-1++, CD4+ and Lin−. DC displayed potent allostimulatory capacity and efficient presentation of KLH and tetanus toxin. DC-primed T cells secreted IFN-γ (Th1); however, no detectable IL-4 (Th2) was noted.DiscussionWe present features of CD34+ DC that have not been previously described. The CD34+ DC generated represent a population of myeloid DC functioning as DC1 but phenoytypically expressing markers characteristic of both DC1 and DC2. This novel DC population is capable of inducing naive T-cell responses and can be expanded to clinically useful numbers. CD34+-derived DC represent attractive candidates for use in adoptive T-cell immunotherapy.