Death Receptor 3 Signaling Controls the Balance between Regulatory and Effector Lymphocytes in SAMP1/YitFc Mice with Crohn's Disease-Like Ileitis.

Death receptor 3 (DR3), a member of the tumor necrosis factor receptor (TNFR) superfamily, has been implicated in regulating T-helper type-1 (TH1), type-2 (TH2), and type-17 (TH17) responses as well as regulatory T cell (Treg) and innate lymphoid cell (ILC) functions during immune-mediated diseases. However, the role of DR3 in controlling lymphocyte functions in inflammatory bowel disease (IBD) is not fully understood. Recent studies have shown that activation of DR3 signaling modulates Treg expansion suggesting that stimulation of DR3 represents a potential therapeutic target in human inflammatory diseases, including Crohn's disease (CD). In this study, we tested a specific DR3 agonistic antibody (4C12) in SAMP1/YitFc (SAMP) mice with CD-like ileitis. Interestingly, treatment with 4C12 prior to disease manifestation markedly worsened the severity of ileitis in SAMP mice despite an increase in FoxP3+ lymphocytes in mesenteric lymph node (MLN) and small-intestinal lamina propria (LP) cells. Disease exacerbation was dominated by overproduction of both TH1 and TH2 cytokines and associated with expansion of dysfunctional CD25-FoxP3+ and ILC group 1 (ILC1) cells. These effects were accompanied by a reduction in CD25+FoxP3+ and ILC group 3 (ILC3) cells. By comparison, genetic deletion of DR3 effectively reversed the inflammatory phenotype in SAMP mice by promoting the expansion of CD25+FoxP3+ over CD25-FoxP3+ cells and the production of IL-10 protein. Collectively, our data demonstrate that DR3 signaling modulates a multicellular network, encompassing Tregs, T effectors, and ILCs, governing disease development and progression in SAMP mice with CD-like ileitis. Manipulating DR3 signaling toward the restoration of the balance between protective and inflammatory lymphocytes may represent a novel and targeted therapeutic modality for patients with CD.

Death receptor 3 signaling enhances proliferation of human regulatory T cells.

Exploiting regulatory T cells (Tregs) to control aberrant immune reactions is a promising therapeutic approach, but is hampered by their relative paucity. In mice, activation of death receptor 3 (DR3), a member of the TNF-receptor superfamily (TNFRSF), increases Treg frequency and efficiently controls exuberant immune activation. For human Tregs, neither DR3 expression nor potential functions have been described. Here, we show that human Tregs express DR3 and demonstrate DR3-mediated activation of p38, ERK, and NFκB. DR3 stimulation enhances Treg expansion ex vivo while retaining their suppressive capacity. In summary, our results establish a functional role for DR3 signaling in human Tregs and could potentially help to tailor Treg-based therapies.

Tregs expanded in vivo by TNFRSF25 agonists promote cardiac allograft survival.

BACKGROUND: Thymic-derived Foxp3(+)CD4(+) regulatory T cells (Tregs)-also called natural Tregs-are critical for the induction and maintenance of transplantation tolerance. Using an agonistic tumor necrosis factor-receptor super family (TNFRSF) 25 antibody, clone 4C12, we showed that TNFRSF25 is a powerful regulator of Treg proliferation-mediating expansion of natural Tregs in vivo. In the present study, we investigate the role of Tregs expanded in vivo by TNFRSF25 on cardiac allograft survival in a mouse model of fully major histocompatibility complex-mismatched ectopic heart transplants. METHODS: C57BL/6 mice were treated with 20 µg of TNFRSF25 agonist 4C12 4 days before heterotopic allogeneic heart transplantation. The survival of the graft was monitored daily by abdominal palpation until the cessation of cardiac contraction. The severity of immune rejection was evaluated by histopathology. Infiltration of inflammatory cells and Tregs into the graft were characterized by flow cytometry. The expression of cytokines and other regulatory proteins was measured by quantitative real-time polymerase chain reaction. RESULTS: Treatment with 4C12 resulted in expansion of Tregs to 30%-35% of CD4(+) cells and was associated with a significant prolongation of median graft survival from 8 days to 17 days (P=0.0049). On day 7 after transplantation, the time point when controls reject the graft, the transplants of 4C12-treated animals beat strongly and showed increased accumulation of Foxp3(+) Tregs within the graft and decreased infiltration of inflammatory cells. CONCLUSIONS: TNFRSF25 agonists expand Tregs in vivo and delay allograft rejection.

Therapeutic Treg expansion in mice by TNFRSF25 prevents allergic lung inflammation.

TNF receptor superfamily member 25 (TNFRSF25; also known as DR3, and referred to herein as TNFR25) is constitutively and highly expressed by CD4(+)FoxP3(+) Tregs. However, its function on these cells has not been determined. Here we used a TNFR25-specific agonistic monoclonal antibody, 4C12, to study the effects of TNFR25 signaling on Tregs in vivo in mice. Signaling through TNFR25 induced rapid and selective expansion of preexisting Tregs in vivo such that they became 30%-35% of all CD4(+) T cells in the peripheral blood within 4 days. TNFR25-induced Treg proliferation was dependent upon TCR engagement with MHC class II, IL-2 receptor, and Akt signaling, but not upon costimulation by CD80 or CD86; it was unaffected by rapamycin. TNFR25-expanded Tregs remained highly suppressive ex vivo, and Tregs expanded by TNFR25 in vivo were protective against allergic lung inflammation, a mouse model for asthma, by reversing the ratio of effector T cells to Tregs in the lung, suppressing IL-13 and Th2 cytokine production, and blocking eosinophil exudation into bronchoalveolar fluid. Our studies define what we believe to be a novel mechanism for Treg control and important functions for TNFR25 in regulating autoaggression that balance its known role in enhancing autoimmunity.