Cryopreservation of mature monocyte-derived human dendritic cells for vaccination: influence on phenotype and functional properties

In the past decade there has been increasing evidence that tumor antigen-loaded dendritic cells (DC) are able to elicit anti-tumor T-cell responses. Initial clinical data for different tumor entities are encouraging, with objective tumor regressions being observed in some patients. Since GMP production of DC for clinical vaccination protocols is a time- and cost-intensive procedure, cryopreservation of DC in aliquots ready for clinical use would significantly facilitate DC-based vaccination in the clinic. We asked whether freezing and thawing alters the phenotype or functional properties of DC. DC from healthy volunteers and from patients with chronic myeloid leukemia (CML) were analyzed after freezing and thawing for their viability, morphology, immunophenotype (FACS profile), T-cell stimulatory capacity (mixed lymphocyte reaction) and mobility (time-lapse cinemicroscopy). Our results demonstrate that cryopreservation does not cause significant changes in the phenotype or function of DC, neither in DC from healthy volunteers nor in those from CML patients. Our data indicate that cryopreserved aliquots of DC are suitable for clinical application in DC-based immunotherapy protocols.