Present in both type 1 diabetes patients and in non-obese diabetic (NOD) mice, a well-studied model of the disease, these T cells employ a variety of mechanisms to bring about beta cell elimination [3]. These include Fas/FasL interactions and perforin- and cytokine-mediated cell killing. Although systemic pharmacological immunosuppression can halt

the autoimmune attack [4], its side effects render it unacceptable for routine use in type 1 diabetes patients. Insulin injections prolong life but are often unable to prevent the serious diabetic complications that are associated with significant morbidity and mortality. Thus, there is an ongoing worldwide effort to develop new strategies for the prevention and treatment of this disease. Nearly two decades ago, Clare-Salzler PLX4720 and colleagues reported that dendritic cells (DCs) isolated from the pancreatic lymph nodes of NOD mice could prevent diabetes development BIBW2992 when transferred adoptively to young recipients [5]. These findings spurred efforts to develop DC-based interventions for type 1 diabetes. The overall favourable safety profile of DC-based therapies revealed by cancer immunotherapy trials has provided further inspiration for such work [6–15]. Here we will discuss the progress that has been made in the area of DC-based therapeutics for type 1 diabetes, with a special emphasis on antigen-specific approaches. We will limit our discussion

to ‘conventional’ DCs, as the therapeutic promise of plasmacytoid DCs in type 1 diabetes has been reviewed recently [16]. The identification of DCs was reported Tenofovir by Steinman and Cohn in 1973

[17], a discovery that was driven by a desire to ‘understand immunogenicity’[18]. One of the initial demonstrations of the immunogenic role of DCs was the finding that isolated murine lymphoid organ DCs were potent stimulators of the mixed leucocyte reaction [19]. However, two decades later, when an antigen was delivered specifically to a subset of murine DCs in vivo (i.e. those expressing the endocytic receptor DEC-205), the predicted outcome of a robust immune response did not occur [20]. Antigen-specific tolerance was observed instead, as cognate T cells were largely deleted or rendered unresponsive. It is now understood that in the steady state (i.e. in the absence of infection), DCs are largely immature and present antigens to T cells in a tolerogenic manner, an activity that is important for the establishment of peripheral tolerance [21]. Such DCs are characterized by low expression of CD40 and the T cell co-stimulatory molecules CD80 and CD86. In contrast, in the case of host exposure to a pathogen, DCs undergo a maturation process, e.g. in response to microbial-derived products, that leads to increased antigen presentation and expression of T cell co-stimulatory molecules and T cell responses of a type appropriate to combat the offending pathogen [22].