Superparamagnetic iron oxide labeling limits the efficacy of rabbit immature dendritic cell vaccination by decreasing their antigen uptake ability in a lysosome-dependent manner.

Immature dendritic cells (iDCs) are for cell transplantation; however, no method has yet been developed for in vivo monitoring the transplanted iDCs. We have explored the feasibility of using superparamagnetic iron oxide (SPIO) labeling and magnetic resonance imaging for in vivo tracking of transplanted iDCs and determined the effects of SPIO labeling on iDC vaccination. With up to 50 μg Fe/ml, SPIO effectively labeled the iDCs without affecting their growth. At or above 100 μg Fe/ml, SPIO caused considerable damage to iDCs. SPIO labeling resulted in autophagosome formation and decreased the uptake of oxidized low density lipoprotein (ox-LDL), an exogenous antigen, by iDCs. SPIO and ox-LDL both localized to the lysosomes, and this competition for lysosomes could be partially responsible for the decreased ox-LDL phagocytic capacity of iDCs due to SPIO labeling.