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
Inflammatory diseases of the CNS, such as MS and its animal model EAE, are characterized by infiltration of activated lymphocytes and phagocytes into the CNS. Within the CNS, activation of resident cells initiates an inflammatory cascade, leading to tissue destruction, demyelination, and neurologic deficit. TLRs recognize microbes and are pivotal mediators of innate immunity. Within the CNS, augmented TLR expression during EAE is observed, even in the absence of any apparent microbial involvement. To determine the functional relevance of this phenomenon during sterile autoimmunity, we studied the role of different TLRs as well as their common signaling adaptor MyD88 in the development of EAE. We found that MyD88–/– mice were completely EAE resistant. Surprisingly, this protection is partly due to engagement of the CpG receptor TLR9. Restricting the MyD88 or TLR9 mutation to host radio-resistant cells, including the cells within the CNS, revealed that engagement of radio-resistant cells modulated the disease course and histopathological changes. Our data clearly demonstrate that both TLR9 and MyD88 are essential modulators of the autoimmune process during the effector phase of disease and suggest that endogenous “danger signals” modulate the disease pathogenesis.
Marco Prinz, Folker Garbe, Hauke Schmidt, Alexander Mildner, Ilona Gutcher, Karina Wolter, Matthias Piesche, Roland Schroers, Elisabeth Weiss, Carsten J. Kirschning, Christian D.P. Rochford, Wolfgang Brück, Burkhard Becher
Complement C5a, a potent anaphylatoxin, is a candidate target molecule for the treatment of inflammatory diseases, such as myocardial ischemia/reperfusion injury, RA, and the antiphospholipid syndrome. In contrast, up until now, no specific contribution of C5a and its receptor, C5aR, was recognized in diseases of antibody-dependent type II autoimmunity. Here we identify C5a as a novel key mediator of autoimmune hemolytic anemia (AIHA) and show that mice lacking C5aR are partially resistant to this IgG autoantibody–induced disease model. Upon administration of anti-erythrocyte antibodies, upregulation of activating Fcγ receptors (FcγRs) on Kupffer cells, as observed in WT mice, was absent in C5aR-deficient mice, and FcγR-mediated in vivo erythrophagocytosis was impaired. Surprisingly, in mice deficient in FcγRI and FcγRIII, anti-erythrocyte antibody–induced C5 and C5a production was abolished, demonstrating the existence of a previously unidentified FcγR-mediated C5a-generating pathway. These results show that the development of a full-blown antibody-dependent autoimmune disease requires C5a — produced by and acting on FcγR — and may suggest therapeutic benefits of C5 and/or C5a/C5aR blockade in AIHA and other diseases closely related to type II autoimmune injury.
Varsha Kumar, Syed R. Ali, Stephanie Konrad, Jörg Zwirner, J. Sjef Verbeek, Reinhold E. Schmidt, J. Engelbert Gessner
Individuals with X-linked lymphoproliferative disease (XLP) display defects in B cell differentiation in vivo. Specifically, XLP patients do not generate a normal number of CD27+ memory B cells, and those few that are present are IgM+. Recent studies have suggested that IgM+CD27+ B cells are not true memory cells, but rather B cells that guard against T cell–independent pathogens. Here we show that human XLP IgM+CD27+ B cells resemble normal memory B cells both morphologically and phenotypically. Additionally, IgM+CD27+ B cells exhibited functional characteristics of normal memory B cells, including the ability to secrete more Ig than naive B cells in response to both T cell–dependent and –independent stimuli. Analysis of spleens from XLP patients revealed a paucity of germinal centers (GCs), and the rare GCs detected were poorly formed. Despite this, Ig variable region genes expressed by XLP IgM+CD27+ B cells had undergone somatic hypermutation to an extent comparable to that of normal memory B cells. These findings reveal a differential requirement for the generation of IgM+ and Ig isotype–switched memory B cells, with the latter only being generated by fully formed GCs. Production of affinity-matured IgM by IgM+CD27+ B cells may protect against pathogens to which a normal immune response is elicited in XLP patients.
Cindy S. Ma, Stefania Pittaluga, Danielle T. Avery, Nathan J. Hare, Irina Maric, Amy D. Klion, Kim E. Nichols, Stuart G. Tangye
Eosinophilic esophagitis (EE) is an emerging disorder with a poorly understood pathogenesis. In order to define disease mechanisms, we took an empirical approach analyzing esophageal tissue by a genome-wide microarray expression analysis. EE patients had a striking transcript signature involving 1% of the human genome that was remarkably conserved across sex, age, and allergic status and was distinct from that associated with non-EE chronic esophagitis. Notably, the gene encoding the eosinophil-specific chemoattractant eotaxin-3 (also known as CCL26) was the most highly induced gene in EE patients compared with its expression level in healthy individuals. Esophageal eotaxin-3 mRNA and protein levels strongly correlated with tissue eosinophilia and mastocytosis. Furthermore, a single-nucleotide polymorphism in the human eotaxin-3 gene was associated with disease susceptibility. Finally, mice deficient in the eotaxin receptor (also known as CCR3) were protected from experimental EE. These results implicate eotaxin-3 as a critical effector molecule for EE and provide insight into disease pathogenesis.
Carine Blanchard, Ning Wang, Keith F. Stringer, Anil Mishra, Patricia C. Fulkerson, J. Pablo Abonia, Sean C. Jameson, Cassie Kirby, Michael R. Konikoff, Margaret H. Collins, Mitchell B. Cohen, Rachel Akers, Simon P. Hogan, Amal H. Assa’ad, Philip E. Putnam, Bruce J. Aronow, Marc E. Rothenberg
Quan Li Zhen, Chun Xie, Tianfu Wu, Meggan Mackay, Cynthia Aranow, Chaim Putterman, Chandra Mohan