Minor role of bystander tolerance to fetal calf serum in a peptide-specific dendritic cell vaccine model against autoimmunity: comparison with serum-free cultures.

Dendritic cells (DCs) are currently considered as promising tools for vaccination against tumors and also autoimmune responses. A major point of concern has been the use of fetal calf serum (FCS) as a source of heterologous antigen in DC cultures. FCS peptides can be presented by the DCs and cause T-cell responses in the recipient. We investigated the role of FCS in an autoimmune model where DC injections can prevent peptide-specifically from experimental autoimmune encephalomyelitis (EAE). We show that murine bone marrow-derived DCs generated in FCS-containing or serum-free media resulting in a similar phenotype, maturation potential, and functions. Peptide-specific protection could be achieved similarly with FCS-DC or serum-free DCs. Although FCS-DC induced strong CD4 T cell proliferation and cytokine production against FCS, these T cells lack antigenic recall during EAE. Even if FCS was reinjected, the effect on EAE resulted only in a 3-day delay of disease onset. Together, our data show that presentation of bystander antigens by peptide-specific DC vaccinations may have little influence on T-cell responses in vivo if the bystander antigen cannot be recalled by specific T cells.