Dendritic Cells Stimulated by Cationic Liposomes

Immunotherapy of cancer aims to harness the immune system to detect and destroy cancer cells. To induce an immune response against cancer, activated dendritic cells (DCs) must present tumor antigens to T lymphocytes of patients. However, cancer patients' DCs are frequently defective, therefore, they are prone to induce rather tolerance than immune responses. In this context, loading tumor antigens into DCs and, at the same time, activating these cells, is a tempting goal within the field. Thus, we investigated the effects of cationic liposomes on the DCs differentiation/maturation, evaluating their surface phenotype and ability to stimulate T lymphocytes proliferation in vitro. The cationic liposomes composed by egg phosphatidylcholine, 1,2-dioleoyl-3-trimethylammonium propane and 1,2-dioleoylphosphatidylethanolamine (50/25/25% molar) were prepared by the thin film method followed by extrusion (65 nm, polydispersity of 0.13) and by the dehydration-rehydration method (95% of the population 107 nm, polydispersity of 0.52). The phenotypic analysis of dendritic cells and the analysis of T lymphocyte proliferation were performed by flow cytometry and showed that both cationic liposomes were incorporated and activated dendritic cells. Extruded liposomes were better incorporated and induced higher CD86 expression for dendritic cells than dehydrated-rehydrated vesicles. Furthermore, dendritic cells which internalized extruded liposomes also provided stronger T lymphocyte stimulation. Thus, cationic liposomes with a smaller size and polydispersity seem to be better incorporated by dendritic cells. Hence, these cationic liposomes could be used as a potential tool in further cancer immunotherapy strategies and contribute to new strategies in immunotherapy.