There is growing evidence that tolerogenic dendritic cells (DCs) play an important role in maintaining peripheral tolerance through the induction of anergic or regulatory T cells. However, in humans, little is known about the ability of tolerogenic DCs to induce tolerance to autoantigens in autoimmune patients. Idiopathic thrombocytopenic purpura (ITP) is an immune-mediated disease in which platelets are destroyed by antiplatelet autoantibodies. Here, we explored in vitro the ability of four subsets of tolerogenic DCs (i.e., immature DCs (imDCs), IL-10-modulated DCs (IL-10-DCs), vasoactive intestinal peptide-modulated DCs (VIP-DCs) or plasmacytoid DCs (pDCs)) derived from patients with ITP, to induce an anergic state or regulatory T cells in autologous platelet glycoprotein (GP)-specific T cells. GPIIb/IIIa-reactive T cells were preincubated with GPIIb/IIIa-loaded imDCs, IL- 10-DCs, pDCs or VIP-DCs, and then rechallenged with autologous mature DCs (mDCs) in the presence of GPIIb/IIIa. Only when T cells were cultured with GPIIb/IIIa-loaded VIP-DCs in primary incubation, inhibited proliferation of GPIIb/IIIa-reactive T cells could be observed at rechallenge with GPIIb/IIIa-loaded mDCs. The anergic state of VIPDC- primed GPIIb/IIIa-reactive T cells could be reversed when rechallenged with GPIIb/ IIIa-loaded mDCs in the presence of a high concentration of exogenous IL-2. Meanwhile, GPIIb/IIIa-reactive T cells were also cultured with VIP-DCs loaded with tetanus toxoid (TT). In contrast to T cells pretreated with GPIIb/IIIa-loaded VIP-DCs, GPIIb/IIIareactive T cells pretreated with TT-loaded VIP-DCs proliferated when rechallenged with GPIIb/IIIa-loaded mDCs, which demonstrated that the induced anergy of autoreactive T cells is antigen specific. Additionally, functional analysis showed that VIP-DC-modulated T cells could not suppress the proliferation of newly induced GPIIb/IIIa-reactive T cells when cocultured with GPIIb/IIIa-loaded mDCs. These results indicated that VIP-DCs could induce autoreactive T cells anergic but not functionally suppressive. Moreover, we found that coculture of VIP-DCs with autologous PBMCs resulted in reduced production of anti-GPIIb/IIIa antibodies, suggesting that GPIIb/IIIa-reactive T cells lost their helper function for inducing autoantibody production by B cells. In contrast, reduced antibody production could not be found when autologous PBMCs were cocultured with imDCs, IL-10-DCs or pDCs. In conclusion, our studies revealed the therapeutic potential of VIPDCs, compared with imDCs, IL-10-DCs or pDCs, to induce autoreactive T-cell anergy to GP antigens, which would in turn facilitate the reestablishment of autoantigen-specific tolerance in patients with ITP.
Disclosures: No relevant conflicts of interest to declare.