Immunophenotypic and functional characterization of cord blood dendritic cells

Dendritic cells (DCs) play a pivotal role in the activation of T cells, which are effector cells in graft-versus-host disease (GVHD). A low incidence of GVHD following cord blood (CB) transplantation has long been reported; despite this, little information is currently available on the characteristics of CB DCs. The goal of the present study was to investigate the immunophenotypic characteristics and distribution of CB DCs and their subsets. For that purpose we have analyzed 15 CB samples as compared to normal peripheral blood (PB) (n = 7) and blood from patients submitted to an allogeneic PB stem cell transplantation (allo-PBSCT) (n = 6). Our results show an overall decreased frequency of DCs in CB due to the presence of significantly lower numbers of CD123inter./CD33inter./CD16+ DCs. Phenotypically, CB DCs displayed a tendency to express lower levels of the gamma-chain interleukin-2 (IL-2) receptor (CD132) and of the CD86 co-stimulatory molecule, supporting a higher degree of immaturity for CB as compared to PB DCs. After activation of CB DCs with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) higher frequencies of cytokine-producing cells were found among CD123inter./CD33inter./CD16+ and CD123dim/CD33bright/CD16- DCs; however, when only the cytokine-producing DCs were considered, a significant decrease in the amount of different cytokine (e.g., IL-1beta and IL-6) produced per cell was observed especially for CD16+ CB DCs. These findings support a higher degree of immaturity for CB as compared to PB DCs that might contribute to explain, at least in part, the low incidence and severity of GVHD observed after CB transplantation.