Immunology
Abstract
Gastrointestinal allergic disorders represent a diverse spectrum of inflammatory diseases that are occurring with increasing incidence and severity. An essential question concerning these disorders is to determine the specific cells and mediators responsible for specific clinical manifestations. With this in mind, we developed a murine model of oral allergen–induced intestinal inflammation accompanied by strong Th2-associated humoral and cellular responses and focused on the immunopathogenesis of allergic diarrhea. Exposure of OVA/alum–sensitized mice to repeated doses of intragastric OVA induced genetically restricted, dose-dependent, acute diarrhea associated with increased intestinal permeability, eosinophilia, and mastocytosis. Mice developed limited systemic manifestations of anaphylaxis, even though they developed marked intestinal mucosal mast cell degranulation. Notably, experiments involving mast cell depletion (with anti–c-kit mAb), anti-IgE treatment, and FcεRI-deficient mice indicated a critical effector role for mast cells in mediating allergic diarrhea. Furthermore, allergic diarrhea was dependent upon synergistic signaling induced by serotonin and platelet-activating factor (PAF), but not histamine. These results demonstrate that oral allergen–induced diarrhea associated with experimental Th2 intestinal inflammation is largely mast cell, IgE, serotonin, and PAF dependent.
Authors
Eric B. Brandt, Richard T. Strait, Dan Hershko, Quan Wang, Emily E. Muntel, Troy A. Scribner, Nives Zimmermann, Fred D. Finkelman, Marc E. Rothenberg
Abstract
CD4+CD25+ regulatory T cells (Treg’s) play a pivotal role in preventing organ-specific autoimmune diseases and in inducing tolerance to allogeneic organ transplants. We and others recently demonstrated that high numbers of Treg’s can also modulate graft-versus-host disease (GVHD) if administered in conjunction with allogeneic hematopoietic stem cell transplantation in mice. In a clinical setting, it would be impossible to obtain enough freshly purified Treg’s from a single donor to have a therapeutic effect. Thus, we performed regulatory T cell expansion ex vivo by stimulation with allogeneic APCs, which has the additional effect of producing alloantigen-specific regulatory T cells. Here we show that regulatory T cells specific for recipient-type alloantigens control GVHD while favoring immune reconstitution. Irrelevant regulatory T cells only mediate a partial protection from GVHD. Preferential survival of specific regulatory T cells, but not of irrelevant regulatory T cells, was observed in grafted animals. Additionally, the use of specific regulatory T cells was compatible with some form of graft-versus-tumor activity. These data suggest that recipient-type specific Treg’s could be preferentially used in the control of GVHD in future clinical trials.
Authors
Aurélie Trenado, Frédéric Charlotte, Sylvain Fisson, Micael Yagello, David Klatzmann, Benoît L. Salomon, José L. Cohen
Abstract
A girl with congenital agammaglobulinemia and minor facial anomalies lacked B cells in peripheral blood: karyotypic analysis of white blood cells showed balanced translocation, t(9;20)(q33.2;q12). In the current study, we isolated a novel gene, leucine-rich repeat–containing 8 (LRRC8), at the translocation site on chromosome 9. It has four transmembrane helixes with one isolated and eight sequentially located leucine-rich repeats (LRRs) and constitutes a new protein family. It is expressed on T cells as well as on B-lineage cells. Translocation truncates the LRRC8 gene, resulting in deletion of the eighth, ninth, and half of the seventh LRR domains located close to the C-terminal. The truncated form of the LRRC8 gene is transcribed with sequences from the noncoding region adjacent to the truncated seventh LRR. Protein products derived from the truncated gene are coexpressed on white blood cells with the intact LRRC8 protein from the untranslocated allele. Transplantation experiments with murine bone marrow cells that were forced to express the truncated LRRC8 show that expression of the truncated protein inhibited B cell development. These results indicate that LRRC8 is responsible for the B cell deficiency in this patient and is required for B cell development.
Authors
Akihisa Sawada, Yoshihiro Takihara, Ji Yoo Kim, Yoshiko Matsuda-Hashii, Sadao Tokimasa, Hiroyuki Fujisaki, Keiko Kubota, Hiroko Endo, Takashi Onodera, Hideaki Ohta, Keiichi Ozono, Junichi Hara
Abstract
T cell homing to sites of injury and inflammation is a critical step for adaptive immune responses. While much has been learned regarding T cell homing to lymphoid tissues, few studies have directly observed trafficking events during an effector response. In this study, we developed a model that uses intravital fluorescence videomicroscopy to determine the molecules critical to T cell rolling within skin allograft microvasculature during the effector phase of the rejection response. Additional studies were performed to quantify T cell infiltrates as rejection progressed. We found that P-selectin and E-selectin expressed on postcapillary venules play overlapping roles in the recruitment of activated T cells in a SCID reconstitution model of skin graft rejection and are important in T cell accumulation at the graft site. Surprisingly, we also found that naive T cells are recruited and accumulate via constitutive T cell L-selectin and upregulated L-selectin ligands on rejecting allograft vasculature. These data indicated that a specific retinue of molecules is upregulated during the rejection response, and they suggest potential future therapeutic targets.
Authors
Thomas R. Jones, Nozomu Shirasugi, Andrew B. Adams, Thomas C. Pearson, Christian P. Larsen
Abstract
Human neutrophil adherence to ECMs induces an initial inhibition of stimulated reactive oxygen species (ROS) formation, followed by an enhanced phase of oxidant production. The initial integrin-mediated suppression of ROS constitutes a mechanism to prevent inappropriate tissue damage as leukocytes migrate to inflammatory sites. The Rac2 guanosine 5′-triphosphatase (GTPase) is a critical regulatory component of the phagocyte NADPH oxidase. We show that activation of Rac2 is inhibited in adherent neutrophils, correlating with inhibition of ROS formation. Conversely, NADPH oxidase components p47 and p67 assemble normally, suggesting a specific action of adhesion on the Rac2 molecular switch. Reconstitution with activated Rac2 restored rapid NADPH oxidase activation kinetics to adherent neutrophils, establishing that inhibition was due to defective Rac2 activity. We provide evidence that integrins inhibit Rac2 activation via a membrane-associated guanine nucleotide exchange factor, likely to be Vav1. Activation of Vav1, but not its upstream activator, Syk, is suppressed by cell adhesion. Vav1 activity is inhibited due to dephosphorylation of the regulatory Tyr174 via enhanced tyrosine phosphatase activity in adherent cells. These studies identify an integrin-mediated pathway in which Vav1 is as a strong candidate for the critical regulatory point in suppression of Rac2 activation and ROS generation during inflammatory responses.
Authors
Tieming Zhao, Valerie Benard, Benjamin P. Bohl, Gary M. Bokoch
Abstract
Notch signaling plays a fundamental role in determining the outcome of differentiation processes in many tissues. Notch signaling has been implicated in T versus B cell lineage commitment, thymic differentiation, and bone marrow hematopoietic precursor renewal and differentiation. Notch receptors and their ligands are also expressed on the surface of mature lymphocytes and APCs, but the effects of Notch signaling in the peripheral immune system remain poorly defined. The aim of the studies reported here was to investigate the effects of signaling through the Notch receptor using a ligand of the Delta-like family. We show that Notch ligation in the mature immune system markedly decreases responses to transplantation antigens. Constitutive expression of Delta-like 1 on alloantigen-bearing cells renders them nonimmunogenic and able to induce specific unresponsiveness to a challenge with the same alloantigen, even in the form of a cardiac allograft. These effects could be reversed by depletion of CD8+ cells at the time of transplantation. Ligation of Notch on splenic CD8+ cells results in a dramatic decrease in IFN-γ with a concomitant enhancement of IL-10 production, suggesting that Notch signaling can alter the differentiation potential of CD8+ cells. These data implicate Notch signaling in regulation of peripheral immunity and suggest a novel approach for manipulating deleterious immune responses.
Authors
Kenneth K. Wong, Matthew J. Carpenter, Lesley L. Young, Susan J. Walker, Grahame McKenzie, Alyson J. Rust, George Ward, Laura Packwood, Karen Wahl, Luc Delriviere, Gerard Hoyne, Paul Gibbs, Brian R. Champion, Jonathan R. Lamb, Margaret J. Dallman
Abstract
CC chemokine ligand 21 (CCL21)/secondary lymphoid chemokine (SLC), a ligand for CC chemokine receptor 7 (CCR7), has been demonstrated to play a vital role in the homing and localization of immune cells to lymphoid tissues, but its role in nonlymphoid tissues largely remains undefined. Here, we provide evidence that CCL21 in lymphoid and nonlymphoid tissues is differentially regulated by lymphotoxin-dependent (LT-dependent) and -independent mechanisms, respectively. This differential regulation is due to the selective regulation of the CCL21-Ser/CCL21a but not the CCL21-Leu/CCL21b gene by the LT and noncanonical NF-κB pathways. This alternate pathway, not dependent on LT or lymphocytes, leading to constitutive expression of CCL21 in nonlymphoid tissues, is critical for the initial recruitment of T lymphocytes to peripheral effector sites. CCL21 expression is subsequently further enhanced in a LT-dependent fashion following airway challenge, potentially facilitating a positive feedback loop to attract additional CCR7+ effector cells. These findings establish an essential role for CCL21 in the recruitment of effector T cells to peripheral tissues and suggest that LT-dependent and -independent regulation of CCL21 plays a role in balancing the central and peripheral immune responses between lymphoid and nonlymphoid tissues.
Authors
James C. Lo, Robert K. Chin, Youjin Lee, Hyung-Sik Kang, Yang Wang, Joel V. Weinstock, Theresa Banks, Carl F. Ware, Guido Franzoso, Yang-Xin Fu
Abstract
CD4+ helper T cells play a critical role in the production of the antinuclear autoantibodies that characterize systemic lupus erythematosus in mice and humans. A key issue is whether this help is derived from a diverse repertoire of autoreactive CD4+ T cells or from a select number of T cells of limited specificity. We used the chronic graft-versus-host disease model to define the diversity of the CD4+ T cell repertoire required to induce the autoantibody response. By transferring clonally restricted versus clonally diverse populations of MHC class II–reactive CD4+ T cells, we show that the loss of B cell tolerance to nuclear antigens has two distinct components with different CD4+ cell requirements. Activation of limited repertoires of CD4+ T cells was sufficient for the expansion of anergized anti–double-stranded DNA B cells and production of IgM autoantibodies. Unexpectedly, we found that CD4+ T cell diversity was necessary for CD4+ T cell trafficking into the follicle and for the generation of isotype-switched IgG autoantibodies. Importantly, combining two limited repertoires of T cells provides sufficient CD4+ T cell diversity to drive antinuclear Ab production. These data demonstrate that a diverse CD4+ T cell repertoire is required to generate a sustained effector B cell response capable of mediating systemic autoimmunity.
Authors
Brian W. Busser, Brigette S. Adair, Jan Erikson, Terri M. Laufer
Abstract
CD4+CD25+ regulatory T (TR) cells have been described in both humans and mice. In mice, TR are thymically derived, and lack of TR leads to organ-specific autoimmunity. Recently, the forkhead/winged helix transcription factor, FoxP3, has been shown to be important for the function of TR cells in mice. In this study, human TR cells were examined and, in results similar to those of studies done in mice, expression of FoxP3 was found exclusively in CD4+CD25+ T cells and correlated with the suppressive activity of these cells. In contrast to the mouse studies, activation of human CD4+CD25– T cells led to expression of FoxP3. Expression of FoxP3 in activated human CD4+CD25+ cells also correlated with suppression of proliferation by these cells in freshly isolated CD4+CD25– T cells from the same donor. This suppression was cell-contact dependent and cytokine independent. Thus, in humans, during activation of CD4+CD25– T cells in an immune response, two populations of cells may arise, effector CD4+CD25+ and regulatory CD4+CD25+ T cells, with expression of FoxP3 correlated with regulatory activity. These data also raise the possibility that a failure to generate peripheral TR cells properly may contribute to autoimmune disease and suggest a possible therapeutic role for FoxP3 in the treatment of such diseases.
Authors
Mindi R.Walker, Deborah J. Kasprowicz, Vivian H. Gersuk, Angéle Bènard, Megan Van Landeghen, Jane H. Buckner, Steven F. Ziegler
Abstract
X-linked anhidrotic ectodermal dysplasia with immunodeficiency (XL-EDA-ID) is caused by hypomorphic mutations in the gene encoding NEMO/IKKγ, the regulatory subunit of the IκB kinase (IKK) complex. IKK normally phosphorylates the IκB-inhibitors of NF-κB at specific serine residues, thereby promoting their ubiquitination and degradation by the proteasome. This allows NF-κB complexes to translocate into the nucleus where they activate their target genes. Here, we describe an autosomal-dominant (AD) form of EDA-ID associated with a heterozygous missense mutation at serine 32 of IκBα. This mutation is gain-of-function, as it enhances the inhibitory capacity of IκBα by preventing its phosphorylation and degradation, and results in impaired NF-κB activation. The developmental, immunologic, and infectious phenotypes associated with hypomorphic NEMO and hypermorphic IKBA mutations largely overlap and include EDA, impaired cellular responses to ligands of TIR (TLR-ligands, IL-1β, and IL-18), and TNFR (TNF-α, LTα1/β2, and CD154) superfamily members and severe bacterial diseases. However, AD-EDA-ID but not XL-EDA-ID is associated with a severe and unique T cell immunodeficiency. Despite a marked blood lymphocytosis, there are no detectable memory T cells in vivo, and naive T cells do not respond to CD3-TCR activation in vitro. Our report highlights both the diversity of genotypes associated with EDA-ID and the diversity of immunologic phenotypes associated with mutations in different components of the NF-κB signaling pathway.
Authors
Gilles Courtois, Asma Smahi, Janine Reichenbach, Rainer Döffinger, Caterina Cancrini, Marion Bonnet, Anne Puel, Christine Chable-Bessia, Shoji Yamaoka, Jacqueline Feinberg, Sophie Dupuis-Girod, Christine Bodemer, Susanna Livadiotti, Francesco Novelli, Paolo Rossi, Alain Fischer, Alain Israël, Arnold Munnich, Françoise Le Deist, Jean-Laurent Casanova
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)