Natural killer T (NKT) cells recognize glycolipid antigens presented by the MHC class I–related glycoprotein CD1d. The in vivo dynamics of the NKT cell population in response to glycolipid activation remain poorly understood. Here, we show that a single administration of the synthetic glycolipid α-galactosylceramide (α-GalCer) induces long-term NKT cell unresponsiveness in mice. NKT cells failed to proliferate and produce IFN-γ upon α-GalCer restimulation but retained the capacity to produce IL-4. Consequently, we found that activation of anergic NKT cells with α-GalCer exacerbated, rather than prevented, B16 metastasis formation, but that these cells retained their capacity to protect mice against experimental autoimmune encephalomyelitis. NKT cell anergy was induced in a thymus-independent manner and maintained in an NKT cell–autonomous manner. The anergic state could be broken by IL-2 and by stimuli that bypass proximal TCR signaling events. Collectively, the kinetics of initial NKT cell activation, expansion, and induction of anergy in response to α-GalCer administration resemble the responses of conventional T cells to strong stimuli such as superantigens. Our findings have important implications for the development of NKT cell–based vaccines and immunotherapies.
Vrajesh V. Parekh, Michael T. Wilson, Danyvid Olivares-Villagómez, Avneesh K. Singh, Lan Wu, Chyung-Ru Wang, Sebastian Joyce, Luc Van Kaer
Pollen exposure induces allergic airway inflammation in sensitized subjects. The role of antigenic pollen proteins in the induction of allergic airway inflammation is well characterized, but the contribution of other constituents in pollen grains to this process is unknown. Here we show that pollen grains and their extracts contain intrinsic NADPH oxidases. The pollen NADPH oxidases rapidly increased the levels of ROS in lung epithelium as well as the amount of oxidized glutathione (GSSG) and 4-hydroxynonenal (4-HNE) in airway-lining fluid. These oxidases, as well as products of oxidative stress (such as GSSG and 4-HNE) generated by these enzymes, induced neutrophil recruitment to the airways independent of the adaptive immune response. Removal of pollen NADPH oxidase activity from the challenge material reduced antigen-induced allergic airway inflammation, the number of mucin-containing cells in airway epithelium, and antigen-specific IgE levels in sensitized mice. Furthermore, challenge with Amb a 1, the major antigen in ragweed pollen extract that does not possess NADPH oxidase activity, induced low-grade allergic airway inflammation. Addition of GSSG or 4-HNE to Amb a 1 challenge material boosted allergic airway inflammation. We propose that oxidative stress generated by pollen NADPH oxidases (signal 1) augments allergic airway inflammation induced by pollen antigen (signal 2).
Istvan Boldogh, Attila Bacsi, Barun K. Choudhury, Nilesh Dharajiya, Rafeul Alam, Tapas K. Hazra, Sankar Mitra, Randall M. Goldblum, Sanjiv Sur
Biglycan, a small leucine-rich proteoglycan, is a ubiquitous ECM component; however, its biological role has not been elucidated in detail. Here we show that biglycan acts in macrophages as an endogenous ligand of TLR4 and TLR2, which mediate innate immunity, leading to rapid activation of p38, ERK, and NF-κB and thereby stimulating the expression of TNF-α and macrophage inflammatory protein–2 (MIP-2). In agreement, the stimulatory effects of biglycan are significantly reduced in TLR4-mutant (TLR4-M), TLR2–/–, and myeloid differentiation factor 88–/– (MyD88–/–) macrophages and completely abolished in TLR2–/–/TLR4-M macrophages. Biglycan-null mice have a considerable survival benefit in LPS- or zymosan-induced sepsis due to lower levels of circulating TNF-α and reduced infiltration of mononuclear cells in the lung, which cause less end-organ damage. Importantly, when stimulated by LPS-induced proinflammatory factors, macrophages themselves are able to synthesize biglycan. Thus, biglycan, upon release from the ECM or from macrophages, can boost inflammation by signaling through TLR4 and TLR2, thereby enhancing the synthesis of TNF-α and MIP-2. Our results provide evidence for what is, to our knowledge, a novel role of the matrix component biglycan as a signaling molecule and a crucial proinflammatory factor. These findings are potentially relevant for the development of new strategies in the treatment of sepsis.
Liliana Schaefer, Andrea Babelova, Eva Kiss, Heinz-J. Hausser, Martina Baliova, Miroslava Krzyzankova, Gunther Marsche, Marian F. Young, Daniel Mihalik, Martin Götte, Ernst Malle, Roland M. Schaefer, Hermann-Josef Gröne
To explore the requirement for M cells and the Peyer’s patch (PP) in induction of oral tolerance and address the potential in vivo role of intestinal epithelial cells as nonprofessional APCs, we have attempted to induce tolerance in mice with ligated small bowel loops without M cells and Peyer’s patches. A 2-centimeter section of vascularized small bowel was spliced away from the gut without disruption of the mesenteric attachments. We introduced OVA directly into the lumen of the loop prior to footpad immunization. By excising segments of bowel that contain PPs in some mice and segments without patches in others, we could study the necessity of the M cell and the underlying patch versus epithelial cells in induction of mucosal tolerance. We show that OVA-specific T cell proliferation and serum antibody responses are reduced in mice that have previously been given OVA both in PP-containing loops and in loops without patches. Furthermore, both high- and low-dose tolerance could be induced in the absence of PPs. Low-dose tolerance is associated with bystander suppression and requires IL-10, which indicates active suppression and the induction of regulatory cells. These data suggest that there is a critical role for components of the mucosal immune system other than PPs in antigen sampling and induction of oral tolerance.
Thomas A. Kraus, Jens Brimnes, Christine Muong, Jian-Hua Liu, Thomas M. Moran, Kelly A. Tappenden, Peter Boros, Lloyd Mayer
Autoantibody production during infections is considered to result from nonspecific activation of low-affinity autoreactive B cells. Whether this can lead to autoimmune disease remains uncertain. We show that chronic infection by Borrelia burgdorferi of Tg animals expressing human rheumatoid factor (RF) B cells (of low or intermediate affinities) in the absence or in the constitutive presence of the autoantigen (represented here by chimeric IgG with human constant region) breaks their state of immunological ignorance, leading to the production of RFs. Surprisingly, this production was more pronounced in intermediate-affinity RF Tg mice coexpressing the autoantigen. This overproduction was mediated by immune complexes and involved synergistic signaling between the B cell receptor and Toll-like receptors and T cell help. These findings indicate that chronic infection can activate autoreactive B cells with significant affinity and creates conditions that can drive them to differentiate into memory cells. Such cells may have some physiological yet undetermined role, but in autoimmune-prone individuals, this scenario may initiate autoimmunity.
Pauline Soulas, Anne Woods, Benoit Jaulhac, Anne-Marie Knapp, Jean-Louis Pasquali, Thierry Martin, Anne-Sophie Korganow
To examine the impact of tumors on the immune system, we compared global gene expression profiles of peripheral blood T cells from previously untreated patients with B cell chronic lymphocytic leukemia (CLL) with those from age-matched healthy donors. Although the cells analyzed were not part of the malignant clone, analysis revealed differentially expressed genes, mainly involved in cell differentiation in CD4 cells and defects in cytoskeleton formation, vesicle trafficking, and cytotoxicity in CD8 cells of the CLL patients. In coculture experiments using CLL cells and T cells from healthy allogeneic donors, similar defects developed in both CD4 and CD8 cells. These changes were induced only with direct contact and were not cytokine mediated. Identification of the specific pathways perturbed in the T cells of cancer-bearing patients will allow us to assess steps to repair these defects, which will likely be required to enhance antitumor immunity.
Güllü Görgün, Tobias A.W. Holderried, David Zahrieh, Donna Neuberg, John G. Gribben
Administration of IL-2 to HIV-infected patients leads to expansion of a unique subset of CD4+CD45RO–CD25+ cells. In this study, the origin, clonality, and function of these cells were investigated. Analysis of TCR excision circles revealed that the CD4+CD45RO–CD25+ cells were the product of peripheral expansion but remained polyclonal as determined by TCR repertoire analysis. Phenotypically, these cells were distinct from naturally occurring Tregs; they exhibited intermediate features, between those of memory and naive cells, and had lower susceptibility to apoptosis than CD45RO–CD25– or memory T cells. Studies of intracellular cytokine production and proliferation revealed that cytokine-expanded naive CD25+ cells had low IL-2 production and required costimulation for proliferation. Despite elevated expression of forkhead transcription factor P3 (foxP3), they exerted only weak suppression compared with CD45RO+CD25+high cells (Tregs). In summary, in vivo IL-2 administration to HIV-infected patients leads to peripheral expansion of a population of long-lived CD4+CD45RO–CD25+ cells that express high levels of foxP3 but exert weak suppressive function. These CD4+CD25+ cytokine-expanded naive cells, distinct from antigen-triggered cells and Tregs, play a role in the maintenance of a state of low turnover and sustained expansion of the CD4+ T cell pool.
Irini Sereti, Hiromi Imamichi, Ven Natarajan, Tomozumi Imamichi, Meena S. Ramchandani, Yunden Badralmaa, Steve C. Berg, Julia A. Metcalf, Barbara K. Hahn, Jean M. Shen, April Powers, Richard T. Davey, Joseph A. Kovacs, Ethan M. Shevach, H. Clifford Lane
Sle3 is an NZM2410-derived lupus susceptibility locus on murine chromosome 7. Congenic recombination has resulted in a novel mouse strain, B6.Sle3, associated with serum antinuclear autoantibodies (ANAs), T cell hyperactivity, and elevated CD4/CD8 ratios. An OVA-specific TCR transgene was used as a tool to demonstrate that Sle3 facilitated heightened T cell expansion in vitro, and in vivo, following antigen challenge. Indeed, continued T cell expansion was noted even in response to a tolerogenic signal. However, these phenotypes did not appear to be T cell intrinsic but were dictated by hyperstimulatory B6.Sle3 APCs. Importantly, B6.Sle3-derived DCs and macrophages appeared to be significantly more mature/activated, less apoptotic, and more proinflammatory and were better at costimulating T cells in vitro, compared with the B6 counterparts. Finally, the adoptive transfer of B6.Sle3-derived DCs into healthy B6 recipients elicited increased CD4/CD8 ratios and serum ANAs, 2 cardinal Sle3-associated phenotypes. We posit that their heightened expression of various costimulatory molecules, including CD80, CD106, I-Ab, and CD40, and their elevated production of various cytokines, including IL-12 and IL-1β, may explain why Sle3-bearing DCs may be superior at breaching self tolerance. These studies provide mechanistic evidence indicating that intrinsic abnormalities in DCs and possibly other myeloid cells may dictate several of the phenotypes associated with systemic lupus, including ANA formation and T cell hyperactivity.
JianKun Zhu, XueBin Liu, Chun Xie, Mei Yan, Ying Yu, Eric S. Sobel, Edward K. Wakeland, Chandra Mohan
Mucosal tolerance prevents pathological reactions against environmental and food antigens, and its failure results in exacerbated inflammation typical of allergies and asthma. One of the proposed mechanisms of oral tolerance is the induction of Tregs. Using a mouse model of hyper-IgE and asthma, we found that oral tolerance could be effectively induced in the absence of naturally occurring thymus-derived Tregs. Oral antigen administration prior to i.p. immunization prevented effector/memory Th2 cell development, germinal center formation, class switching to IgE, and lung inflammation. Oral exposure to antigen induced development of antigen-specific CD4+CD25+Foxp3+CD45RBlow cells that were anergic and displayed suppressive activity in vivo and in vitro. Oral tolerance to the Th2 allergic response was in large part dependent on TGF-β and independent of IL-10. Interestingly, Tregs were also induced by single i.p. immunization with antigen and adjuvant. However, unlike oral administration of antigen, which induced Tregs but not effector T cells, i.p. immunization led to the simultaneous induction of Tregs and effector Th2 cells displaying the same antigen specificity.
Daniel Mucida, Nino Kutchukhidze, Agustin Erazo, Momtchilo Russo, Juan J. Lafaille, Maria A. Curotto de Lafaille
CD4+CD25+ Tregs play a central role in the maintenance of peripheral self tolerance by keeping autoreactive T cells in check. Whereas the thymic origin of CD4+CD25+ Tregs, as a distinct lineage, has been inferred, understanding of their developmental pathways has remained elusive. In both mice and humans, peripheral CD4+CD25+ Treg populations have been described as composed of antigen-experienced T cells that fail to significantly proliferate following TCR stimulation but suppress proliferation and effector functions of CD25– T cells. Here we show that analysis of CD25 expression in human circulating CD4+ T lymphocytes with respect to their in vivo differentiation stages identifies a distinct subset of CD25+CCR7+CD62L+CTLA-4+FOXP3+ cells contained in the CD45RA+/RO– naive fraction. The subset, which we have named natural naive Tregs (NnTregs), is prominent in young adults and decreases with age together with the total naive CD4+ population. NnTregs are anergic following stimulation in the absence of IL-2 and exert ex vivo cell-cell contact–mediated suppressor functions. In addition, they proliferate in response to stimulation with autologous APCs, which indicates a high enrichment in T cells bearing self-reactive TCRs. The definition of this subset has important implications for the analysis of human naturally occurring Tregs and for their targeting in therapeutic immune interventions.
Danila Valmori, Andrea Merlo, Naira E. Souleimanian, Charles S. Hesdorffer, Maha Ayyoub