Type 1 diabetes mellitus is a chronic inflammatory disease in which the insulin and glutamic acid decarboxylase producing β-cells of the pancreatic islets are killed by autoreactive cells of the immune system in response to a loss of tolerance. Early experiments showed that self-tolerance could be partially restored by oral inoculation with small amounts of insulin. Later experiments showed that insulin autoantigen induced immune tolerance could be greatly enhanced by linkage of β-cell autoantigens (Auto Ag) to adjuvant molecules such as the non-toxic cholera enterotoxin B subunit (CTB).

To identify mechanisms responsible for CTB-autoantigen fusion protein suppression of diabetes autoimmunity, dendritic cells (DCs), a major class of antigen presenting cells (APC) involved in restoration of immunological tolerance, were differentiated from umbilical cord blood monocytes and incubated with recombinant CTB- pro-insulin and CTB-glutamic acid decarboxylase adjuvant-autoantigen fusion proteins. The fusion proteins were shown to dramatically suppress DC biosynthesis of costimulatory factors and proinflammatory cytokines IL-12 and IL-6 required for autoreactive T cell development. In addition, a substantial increase in DC secretion of the anti-inflammatory cytokine IL-10 was also detected further confirming the previous observation. Naive T cells incubated with CTB-autoantigen inoculated DCs developed into mature T cells that synthesized IL-10 and TGF-β cytokines indicative of Th2, Tr1 and Th3 regulatory T cell populations involved in suppression of CD4+ and CD8+ T lymphocytes responsible for the initiation of diabetes autoimmunity. Further, vaccine inoculated DCs suppressed T cell pro-inflammatory cytokines IFN-γ, IL-17 and IL-2 guiding T cell morphogenesis in the direction of tolerance rather than toward inflammation responsible for diabetes onset. In summary: the experimental results presented in this Dissertation indicate that ex vivo vaccination of human DCs favors immunological suppression of diabetes development and suggests that mechanisms of immunological tolerance responsible for multicomponent vaccine suppression of diabetes onset and possibly progression are comparable in humans and in animals.