Abstract
Background aims
Polarized mature dendritic cells (DC) can activate cytolytic T-lymphocyte (CTL) responses and may be a more effective clinical strategy in DC-based cancer vaccines. A subset of mature DC can down-regulate the T-cell immune response through expression of indoleamine-2,3-dioxygenase (IDO). We determined whether polarizing DC ex vivo increased IDO expression and activity.
Methods
Peripheral blood monocytes from healthy volunteers were cultured ex vivo in polarizing and non-polarizing culture conditions. DC IDO expression was detected by Western blot. IDO enzyme activity was determined by high-performance liquid chromatography (HPLC) measurement of kynurenine (K) and tryptophan (T) concentrations in culture supernatants.
Results
IDO protein was markedly increased in DC after polarization (median 1222.4%, range 331.5–2113.3%) versus non-polarized DC (median 28.3%, range 3.7–119.8%; P=0.04). The median K/T ratio was significantly higher in polarized DC versus non-polarized DC (6.34, range 6.02–6.65, versus 0.047, range 0.004–0.541; P=0.04). IDO protein expression correlated with enzyme activity (r=0.80, P=0.002).
Conclusions
DC polarizing culture conditions increased expression of IDO protein and IDO enzyme activity. DC culture and maturation methodologies may impact the effectiveness of adoptive DC therapy.
Acknowledgments
Supported, in part, by NIH grant RO1 CA5648 and Cancer Center Support Grant NIH CA 23108.
Declaration of Interest: The authors report no coflict of interest. The author alone are responsible for the content and writing of the paper.