The immune system is capable of mounting robust responses against invading pathogens but refrains from attacking self. Many studies have focused on tolerance induction of Th1 cells, whose failure results in development of autoimmune diseases. However, the molecular mechanisms governing tolerance induction in Th2 cells and its relation to allergic responses remain unclear. Here we used both in vivo and in vitro protocols to demonstrate that Th2 cells either containing a mitogen and extracellular kinase kinase 1 (MEKK1) mutant or lacking JNK1 or the E3 ubiquitin ligase Itch cannot be tolerized. In a mouse allergic model, injection of high-dose tolerizing antigen failed to block the development of airway inflammation in Itch–/– mice. This study suggests that MEKK1-JNK signaling regulates Itch E3 ligase–mediated tolerogenic process in Th2 cells. These findings have therapeutic implications for allergic diseases.
K. Venuprasad, Chris Elly, Min Gao, Shahram Salek-Ardakani, Yohsuke Harada, Jun-Li Luo, Chun Yang, Michael Croft, Kazushi Inoue, Michael Karin, Yun-Cai Liu
Human T cell leukemia virus type 1 (HTLV-1) infects both CD4+ and CD8+ lymphocytes, yet it induces adult T cell leukemia/lymphoma (ATLL) that is regularly of the CD4+ phenotype. Here we show that in vivo infected CD4+ and CD8+ T cells displayed similar patterns of clonal expansion in carriers without malignancy. Cloned infected cells from individuals without malignancy had a dramatic increase in spontaneous proliferation, which predominated in CD8+ lymphocytes and depended on the amount of tax mRNA. In fact, the clonal expansion of HTLV-1–positive CD8+ and CD4+ lymphocytes relied on 2 distinct mechanisms — infection prevented cell death in the former while recruiting the latter into the cell cycle. Cell cycling, but not apoptosis, depended on the level of viral-encoded tax expression. Infected tax-expressing CD4+ lymphocytes accumulated cellular defects characteristic of genetic instability. Therefore, HTLV-1 infection establishes a preleukemic phenotype that is restricted to CD4+ infected clones.
David Sibon, Anne-Sophie Gabet, Marc Zandecki, Christiane Pinatel, Julien Thête, Marie-Hélène Delfau-Larue, Samira Rabaaoui, Antoine Gessain, Olivier Gout, Steven Jacobson, Franck Mortreux, Eric Wattel
Emerging evidence suggests critical roles for APCs in suppressing immune responses. Here, we show that zymosan, a stimulus for TLR2 and dectin-1, regulates cytokine secretion in DCs and macrophages to induce immunological tolerance. First, zymosan induces DCs to secrete abundant IL-10 but little IL-6 and IL-12(p70). Induction of IL-10 is dependent on TLR2- and dectin-1–mediated activation of ERK MAPK via a mechanism independent of the activation protein 1 (AP-1) transcription factor c-Fos. Such DCs stimulate antigen-specific CD4+ T cells poorly due to IL-10 and the lack of IL-6. Second, zymosan induces F4-80+ macrophages in the splenic red pulp to secrete TGF-β. Consistent with these effects on APCs, injection of zymosan plus OVA into mice results in OVA-specific T cells that secrete little or no Th1 or Th2 cytokines, but secrete robust levels of IL-10, and are unresponsive to challenge with OVA plus adjuvant. Finally, coinjection of zymosan with OVA plus LPS suppresses the response to OVA via a mechanism dependent on IL-10, TGF-β, and lack of IL-6. Together, our data demonstrate that zymosan stimulates IL-10+IL-12(p70)–IL-6low regulatory DCs and TGF-β+ macrophages to induce immunological tolerance. These data suggest several targets for pharmacological modulation of immune responses in various clinical settings.
Stephanie Dillon, Sudhanshu Agrawal, Kaustuv Banerjee, John Letterio, Timothy L. Denning, Kyra Oswald-Richter, Deborah J. Kasprowicz, Kathryn Kellar, Jeff Pare, Thomas van Dyke, Steven Ziegler, Derya Unutmaz, Bali Pulendran
IFN regulatory factor 4–binding (IRF-4–binding) protein (IBP) is a novel type of activator of Rho GTPases that is recruited to the immunological synapse upon TCR stimulation. Here we demonstrate that loss of IBP leads to the spontaneous development of a systemic autoimmune disorder characterized by the accumulation of effector/memory T cells and IgG+ B cells, profound hypergammaglobulinemia, and autoantibody production. Similar to human SLE, this syndrome primarily affects females. T cells from IBP-deficient mice are resistant to death in vitro as well as in vivo and exhibit selective defects in effector function. In the absence of IBP, T cells respond suboptimally to TCR engagement, as demonstrated by diminished ERK1/2 activation, decreased c-Fos induction, impaired immunological synapse formation, and defective actin polymerization. Transduction of IBP-deficient T cells with a WT IBP protein, but not with an IBP mutant lacking the Dbl-like domain required for Rho GTPase activation, rescues the cytoskeletal defects exhibited by these cells. Collectively, these findings indicate that IBP, a novel regulator of Rho GTPases, is required for optimal T cell effector function, lymphocyte homeostasis, and the prevention of systemic autoimmunity.
Jessica C. Fanzo, Wen Yang, So Young Jang, Sanjay Gupta, Qinzhong Chen, Ayesha Siddiq, Steven Greenberg, Alessandra B. Pernis
Antagonists to α4 integrin show promise for several autoimmune and inflammatory diseases but may exhibit mechanism-based toxicities. We tested the capacity of blockade of α4 integrin signaling to perturb functions involved in inflammation, while limiting potential adverse effects. We generated and characterized mice bearing a Y991A mutation in α4 integrin [α4(Y991A) mice], which blocks paxillin binding and inhibits α4 integrin signals that support leukocyte migration. In contrast to the embryonic-lethal phenotype of α4 integrin–null mice, mice bearing the α4(Y991A) mutation were viable and fertile; however, they exhibited defective recruitment of mononuclear leukocytes into thioglycollate-induced peritonitis. α4 Integrins are essential for definitive hematopoiesis; however, the α4(Y991A) mice had intact lymphohematopoiesis and, with the exception of reduced Peyer’s patches, normal architecture and cellularity of secondary lymphoid tissues. We conclude that interference with α4 integrin signaling can selectively impair mononuclear leukocyte recruitment to sites of inflammation while sparing vital functions of α4 integrins in development and hematopoiesis.
Chloé C. Féral, David M. Rose, Jaewon Han, Norma Fox, Gregg J. Silverman, Kenneth Kaushansky, Mark H. Ginsberg
Kaposi sarcoma–associated herpesvirus (KSHV) is a human lymphotropic herpesvirus. It is implicated in B cell neoplasias such as primary effusion lymphoma and multicentric Castleman disease in AIDS patients. The KSHV latency-associated nuclear antigen (LANA) is consistently expressed in all KSHV-associated tumor cells and was shown to bind the tumor suppressor proteins p53 and pRb. To test LANA’s contribution to lymphomagenesis in vivo we generated transgenic mice expressing LANA under the control of its own promoter, which is B cell specific. All of the transgenic mice developed splenic follicular hyperplasia due to an expansion of IgM+IgD+ B cells and showed increased germinal center formation. We also observed lymphomas, implying that LANA can activate B cells and provide the first step toward lymphomagenesis.
Farnaz D. Fakhari, Joseph H. Jeong, Yogita Kanan, Dirk P. Dittmer
Although it has long been hypothesized that allergen immunotherapy inhibits allergy, in part, by inducing production of IgG Abs that intercept allergens before they can cross-link mast cell FcεRI-associated IgE, this blocking Ab hypothesis has never been tested in vivo. In addition, evidence that IgG-allergen interactions can induce anaphylaxis by activating macrophages through FcγRIII suggested that IgG Ab might not be able to inhibit IgE-mediated anaphylaxis without inducing anaphylaxis through this alternative pathway. We have studied active and passive immunization models in mice to approach these issues and to determine whether any inhibition of anaphylaxis observed was a direct effect of allergen neutralization by IgG Ab or an indirect effect of cross-linking of FcεRI to the inhibitory IgG receptor FcγRIIb. We demonstrate that IgG Ab produced during the course of an immune response or administered passively can completely suppress IgE-mediated anaphylaxis; that these IgG blocking Abs inhibit IgE-mediated anaphylaxis without inducing FcγRIII-mediated anaphylaxis only when IgG Ab concentration is high and challenge allergen dose is low; that allergen epitope density correlates inversely with the allergen dose required to induce both IgE- and FcγRIII-mediated anaphylaxis; and that both allergen interception and FcγRIIb-dependent inhibition contribute to in vivo blocking Ab activity.
Richard T. Strait, Suzanne C. Morris, Fred D. Finkelman
CD154 is a cell surface molecule expressed on activated T cells that binds to CD40, an activating molecule on APCs. Its blockade has been shown to prevent allograft rejection, presumably by interrupting interactions between T cells and APCs. It is known that activated human platelets express and shed CD154 and can induce APC activation and other immune processes in vitro. Here we show that platelet-derived CD154 is sufficient to initiate cardiac allograft rejection independent of any cellular source of this molecule. CD154-KO mice reject cardiac allografts after receiving CD154-expressing human platelets or recombinant CD154 (rCD154) trimers. Treatment with the human CD154-specific mAb 5c8 specifically prevents this induced rejection. Soluble trimers, but not platelets, induce rejection when infused temporally remote from the surgical procedure, suggesting that surgically induced platelet activation is required for CD154 release. Allograft rejection can thus be instigated by activated platelets through CD154. These data implicate platelets as a proximal component of acquired alloimmunity, providing insight into the mechanisms of allograft rejection and the physiological response to trauma in general.
He Xu, Xiaojie Zhang, Roslyn B. Mannon, Allan D. Kirk
Tregs play a central role in the suppression of immune reactions and prevention of autoimmune responses harmful to the host. During acute infection, however, Tregs might hinder effector T cell activity directed toward the elimination of the pathogenic challenge. Pathogen recognition receptors from the TLR family expressed by innate immune cells are crucial for the generation of effective immunity. We have recently shown the CD4+CD25+ Treg subset in TLR2–/– mice to be significantly reduced in number compared with WT littermate control mice, indicating a link between Tregs and TLR2. Here, we report that the TLR2 ligand Pam3Cys, but not LPS (TLR4) or CpG (TLR9), directly acts on purified Tregs in a MyD88-dependent fashion. Moreover, when combined with TCR stimulation, TLR2 triggering augmented Treg proliferation in vitro and in vivo and resulted in a temporal loss of the suppressive Treg phenotype in vitro by directly affecting Tregs. Importantly, WT Tregs adoptively transferred into TLR2–/– mice were neutralized by systemic administration of TLR2 ligand during the acute phase of a Candida albicans infection, resulting in a 100-fold reduced C. albicans outgrowth. This demonstrates that in vivo TLR2 also controls the function of Tregs and establishes a direct link between TLRs and the control of immune responses through Tregs.
Roger P.M. Sutmuller, Martijn H.M.G.M. den Brok, Matthijs Kramer, Erik J. Bennink, Liza W.J. Toonen, Bart-Jan Kullberg, Leo A. Joosten, Shizuo Akira, Mihai G. Netea, Gosse J. Adema
The transcription factor T-bet (Tbx21) plays a major role in adaptive immunity and is required for optimal IFN-γ production by DCs. Here we demonstrate an essential function for T-bet in DCs in controlling inflammatory arthritis. We show that collagen antibody–induced arthritis (CAIA), a model of human RA, is a bipartite disease characterized by an early innate immune system component intact in RAG2–/– mice and a later adaptive immune system phase. Mice lacking T-bet had markedly reduced joint inflammation at both early and late time points and RAG2–/–T-bet–/– double-deficient mice were essentially resistant to disease. Remarkably, adoptive transfer of T-bet–expressing DCs reconstituted inflammation in a T-bet deficient and T-bet/RAG2–deficient milieu. T-bet regulates the production of proinflammatory cytokine IL-1α and chemokines macrophage inflammatory protein-1α (MIP-1α) and thymus- and activation-related chemokine (TARC) by DCs. Further, T-bet expression in DCs is required for T helper cell activation. We conclude that T-bet plays a vital function in DCs that links innate and adaptive immunity to regulate inflammatory responses. T-bet provides an attractive new target for the development of novel therapeutics for inflammatory arthritis.
Jingsong Wang, John W. Fathman, Geanncarlo Lugo-Villarino, Lucila Scimone, Ulrich von Andrian, David M. Dorfman, Laurie H. Glimcher