Freezing of dendritic cells, generated from cryopreserved leukaphereses, does not influence their ability to induce antigen-specific immune responsesor functionally react to maturation stimuli

It is of practical clinical importance to be able to reinfuse into patients dendritic cells which have been previously frozen in aliquots. However, th ere are few studies comparing the function of fresh and frozen dendritic ce lls. We therefore decided to perform a systematic immunophenotypic and func tional comparison of fresh and frozen dendritic cells. We chose to assess f unctional properties using proliferation tests and evaluating the preservat ion of specific antigens presentation in the context of MHC class II. Dendr itic cells, generated from leukaphereses of normal volunteers, were loaded with proteins by a 2-h incubation at a protein concentration of 50 mu g/ml, and were thereafter used fresh or after freeze-thawing in an IFN gamma Eli spot assay. The IFN gamma release from antigen specific T cells was not aff ected by liquid nitrogen storage of pulsed immature dendritic cells. In the same way, the storage did not alter their stimulatory properties for antig en specific autologous T cells or for allogeneic CD8+ T lymphocytes in a pr oliferation assay. We also showed that freezing non-pulsed immature dendrit ic cells did not alter their capacity to capture, process and generate anti gen-specific reactions once thawed, nor did it impair their capacity to acq uire fully mature characteristics using CD40L and IFN gamma, with respect t o immunophenotype and bioactive IL-12. secretion. (C) 2000 Elsevier Science B.V. All rights reserved.