This finding is consistent with the speculation [57] that intravenously administered DCs can acquire islet antigens in vivo (a process that would take place in the pancreatic lymph nodes) and, thus, can modulate effector and regulatory T cell responses to diabetes-relevant antigens even without deliberate prior antigen treatment. The original observation that DCs from the pancreatic

lymph nodes could prevent diabetes when transferred to NOD mice, while those from other sites could not, suggested the potential importance of the incorporation of beta cell antigens into DC-based therapeutics for this disease [5]. As reviewed recently [66], a variety of immunosuppressive and anti-inflammatory compounds, e.g. vitamin D3 and mycophenolate mofetil, PI3K Inhibitor Library in vivo can endow DCs with a tolerogenic functional phenotype. Cytokines such as IL-10 can behave similarly [67]

. This suggests a therapeutic strategy for type 1 diabetes in which tolerogenic DCs would be generated in GPCR Compound Library cell assay vitro and then exposed to beta cell antigens prior to administration. Such an approach was employed recently by the von Herrath group [59], who utilized the rat insulin promoter (RIP)-LCMV model of type 1 diabetes in which disease is induced upon LCMV infection. BMDCs were generated in the presence of GM-CSF, IL-10 and normal mouse serum, and then pulsed with a viral peptide recognized by CD8+ T cells. When the pulsed DCs were administered intraperitoneally to mice 10 and 3 days prior to LCMV infection, only 45% of the animals developed diabetes, whereas 80% of those treated with unpulsed DCs became diabetic. A reduced expansion of viral-specific T cells in response to viral infection was also observed

in mice treated with peptide-pulsed DCs. This study supports the idea that ex vivo-generated tolerogenic DCs, when exposed to disease-relevant antigens, can deliver therapeutic benefit in type 1 diabetes. In a recent thoughtful review of DC-based immunotherapeutic strategies for human diseases, the disadvantages of ex vivo antigen loading of DCs were discussed [68]. These include a requirement for leukapheresis, the inability to manipulate DCs N-acetylglucosamine-1-phosphate transferase within their natural milieu and a requirement for a tailor-made ‘product’ for each patient, resulting in labour-intensive procedures and high costs. It is for reasons such as these that we [69] and others [70] are exploring the utility of in vivo delivery of beta cell antigens to DCs in the prevention and treatment of type 1 diabetes. DCs employ a variety of molecules, such as the Fc receptors, the macrophage mannose receptor (MMR) and DEC-205 [71], to execute receptor-mediated endocytosis of antigens. Of these, DEC-205 (Ly75/CD205) has the special ability to uptake and subsequently present antigen via both class I [35] and class II MHC pathways [72]. DEC-205 is a type 1 transmembrane protein homologous to MMR and phospholipase A2 [71].