Presentation of tetanus toxoid to autologous T cells by dendritic cells generated from human blood. Improved specificity with dendritic cells generated without fetal calf serum.

Dendritic cells (DC) are highly specialised to initiate primary immune responses and may therefore serve as natural adjuvant in future strategies for specific immunotherapy, e. g. with tumor antigens. The originally developed culture system to generate DC from peripheral human blood with GM-CSF and IL-4 was dependent on the use of fetal calf serum. We employed such DC as antigen presenting cells in a modified lymphocyte proliferation assay to measure the response of autologous T cells to tetanus toxoid. However, a substantial proliferative response of T cells was also observed in control wells without antigen, i.e. in the setting of a syngeneic mixed leukocyte reaction. This makes it difficult, if not impossible, to monitor antigen-specific responses in vitro. In a recently developed improved method fetal calf serum was replaced by 1% autologous human plasma. Using such DC in our lymphocyte proliferation assay background proliferation was markedly reduced. T cell responses to tetanus toxoid were strongest when the antigen was added to DC three days before cocultivation with T cells. We conclude that DC cultured in FCS-free autologous systems, suitable for clinical use, can process and present tetanus protein to autologous T cells. Using such DC in a lymphocyte proliferation assay may facilitate the measurement of antigen-specific T cell responses.