bluuebunny/crossref_metadata_2025 huggingface dataset:
CD23 Trimers Are Preassociated on the Cell Surface Even in the Absence of Its Ligand, IgE
Authors: Kilmon Michelle A. , Shelburne Anne E. , Chan-Li Yee , Holmes Kevin L. , Conrad Daniel H.
Published: April 2014

Allergic disease is mediated by high levels of allergen-specific IgE. IgE binding to CD23, the low affinity receptor for IgE, results in a negative feedback signal leading to a decrease in IgE production. Previous studies have shown that CD23 associates as an oligomer and that cooperative binding of at least two lectin domains is required for high affinity IgE binding to CD23. We have previously shown that cooperative binding is required for regulation of IgE production. This study describes the production of several mAbs that bind the stalk region of murine CD23. One of the Abs, 19G5, inhibited the IgE/CD23 interaction at 37°C, but not at 4°C. Analysis of the binding properties of these Abs revealed that CD23 dissociates at high temperatures, such as 37°C; however, the N terminus is constitutively associated, indicating partial, rather than complete, dissociation. A novel finding was that the stalk region, previously thought to mediate trimer association, was not required for oligomerization. These data reveal important information about the structure of CD23 that may be useful in modulating IgE production.
Wnt Target Genes Identified by DNA Microarrays in Immature CD34+ Thymocytes Regulate Proliferation and Cell Adhesion
Authors: Staal Frank J. T. , Weerkamp Floor , Baert Miranda R. M. , van den Burg Caroline M. M. , van Noort Mascha , de Haas Edwin F. E. , van Dongen Jacques J. M.
Published: April 2014

The thymus is seeded by very small numbers of progenitor cells that undergo massive proliferation before differentiation and rearrangement of TCR genes occurs. Various signals mediate proliferation and differentiation of these cells, including Wnt signals. Wnt signals induce the interaction of the cytoplasmic cofactor β-catenin with nuclear T cell factor (TCF) transcription factors. We identified target genes of the Wnt/β-catenin/TCF pathway in the most immature (CD4−CD8−CD34+) thymocytes using Affymetrix DNA microarrays in combination with three different functional assays for in vitro induction of Wnt signaling. A relatively small number (∼30) of genes changed expression, including several proliferation-inducing transcription factors such as c-fos and c-jun, protein phosphatases, and adhesion molecules, but no genes involved in differentiation to mature T cell stages. The adhesion molecules likely confine the proliferating immature thymocytes to the appropriate anatomical sites in the thymus. For several of these target genes, we validated that they are true Wnt/β-catenin/TCF target genes using real-time quantitative PCR and reporter gene assays. The same core set of genes was repressed in Tcf-1-null mice, explaining the block in early thymocyte development in these mice. In conclusion, Wnt signals mediate proliferation and cell adhesion, but not differentiation of the immature thymic progenitor pool.
The Epidermal Growth Factor-Seven Transmembrane (EGF-TM7) Receptor CD97 Is Required for Neutrophil Migration and Host Defense
Authors: Leemans Jaklien C. , te Velde Anje A. , Florquin Sandrine , Bennink Roelof J. , de Bruin Kora , van Lier René A. W. , van der Poll Tom , Hamann Jörg
Published: April 2014

The epidermal growth factor-seven transmembrane (EGF-TM7) family is a group of seven-span transmembrane receptors predominantly expressed by cells of the immune system. Family members CD97, EGF module-containing mucin-like receptor (EMR) 1, EMR2, EMR3, EMR4, and EGF-TM7-latrophilin-related protein are characterized by an extended extracellular region with a variable number of N-terminal EGF-like domains. EGF-TM7 receptors bind cellular ligands as demonstrated by the interaction of CD97 with decay accelerating factor (CD55) and dermatan sulfate. Investigating the effect of newly generated mAb on the migration of neutrophilic granulocytes, we here report for the first time in vivo data on the function of CD97. In dextran sulfate sodium-induced experimental colitis, we show that homing of adoptively transferred neutrophils to the colon was significantly delayed when cells were preincubated with CD97 mAb. The consequences of this defect in neutrophil migration for host defense are demonstrated in a murine model of Streptococcus pneumoniae-induced pneumonia. Mice treated with CD97 mAb to EGF domain 1 (1B2) and EGF domain 3 (1C5) displayed a reduced granulocytic inflammatory infiltrate at 20 h after inoculation. This was associated with a significantly enhanced outgrowth of bacteria in the lungs at 44 h and a strongly diminished survival. Together, these findings indicate an essential role for CD97 in the migration of neutrophils.
The Cationic Antimicrobial Peptide LL-37 Modulates Dendritic Cell Differentiation and Dendritic Cell-Induced T Cell Polarization
Authors: Davidson Donald J. , Currie Andrew J. , Reid Gregor S. D. , Bowdish Dawn M. E. , MacDonald Kelly L. , Ma Rebecca C. , Hancock Robert E. W. , Speert David P.
Published: April 2014

Dendritic cells (DC) are instrumental in orchestrating an appropriately polarized Th cell response to pathogens. DC exhibit considerable phenotypic and functional plasticity, influenced by lineage, Ag engagement, and the environment in which they develop and mature. In this study, we identify the human cationic peptide LL-37, found in abundance at sites of inflammation, as a potent modifier of DC differentiation, bridging innate and adaptive immune responses. LL-37-derived DC displayed significantly up-regulated endocytic capacity, modified phagocytic receptor expression and function, up-regulated costimulatory molecule expression, enhanced secretion of Th-1 inducing cytokines, and promoted Th1 responses in vitro. LL-37 may be an attractive therapeutic candidate for manipulating T cell polarization by DC.
Mice Deficient in LRG-47 Display Increased Susceptibility to Mycobacterial Infection Associated with the Induction of Lymphopenia
Authors: Feng Carl G. , Collazo-Custodio Carmen M. , Eckhaus Michael , Hieny Sara , Belkaid Yasmine , Elkins Karen , Jankovic Dragana , Taylor Gregory A. , Sher Alan
Published: April 2014

Although IFN-γ is essential for host control of mycobacterial infection, the mechanisms by which the cytokine restricts pathogen growth are only partially understood. LRG-47 is an IFN-inducible GTP-binding protein previously shown to be required for IFN-γ-dependent host resistance to acute Listeria monocytogenes and Toxoplasma gondii infections. To examine the role of LRG-47 in control of mycobacterial infection, LRG-47−/− and wild-type mice were infected with Mycobacterium avium, and host responses were analyzed. LRG-47 protein was strongly induced in livers of infected wild-type animals in an IFN-γ-dependent manner. LRG-47−/− mice were unable to control bacterial replication, but survived the acute phase, succumbing 11–16 wk postinfection. IFN-γ-primed, bone marrow-derived macrophages from LRG-47−/− and wild-type animals produced equivalent levels of TNF and NO upon M. avium infection in vitro and developed similar intracellular bacterial loads. In addition, priming for IFN-γ production was observed in T cells isolated from infected LRG-47−/− mice. Importantly, however, mycobacterial granulomas in LRG-47−/− mice showed a marked lymphocyte deficiency. Further examination of these animals revealed a profound systemic lymphopenia and anemia triggered by infection. As LRG47−/− T lymphocytes were found to both survive and confer resistance to M. avium in recipient recombinase-activating gene-2−/− mice, the defect in cellular response and bacterial control in LRG-47−/− mice may also depend on a factor(s) expressed in a nonlymphocyte compartment. These findings establish a role for LRG-47 in host control of mycobacteria and demonstrate that in the context of the IFN-γ response to persistent infection, LRG-47 can have downstream regulatory effects on lymphocyte survival.
Prostaglandin E2 Induces Degranulation-Independent Production of Vascular Endothelial Growth Factor by Human Mast Cells
Authors: Abdel-Majid Raja M. , Marshall Jean S.
Published: April 2014

Mast cells accumulate in large numbers at angiogenic sites, where they have been shown to express a number of proangiogenic factors, including vascular endothelial growth factor (VEGF-A). PGE2 is known to strongly promote angiogenesis and is found in increased levels at sites of chronic inflammation and around solid tumors. The expression pattern of VEGF and the regulation of VEGF-A by PGE2 were examined in cord blood-derived human mast cells (CBMC). CBMC expressed mRNA for five isoforms of VEGF-A and other members of the VEGF family (VEGF-B, VEGF-C, and VEGF-D) with strong expression of the most potent secretory isoforms. PGE2 was a very strong inducer of VEGF-A121/165 production by CBMC and also elevated VEGF-A mRNA expression. The amount of VEGF-A121/165 protein production induced by PGE2 was 4-fold greater than that induced by IgE-mediated activation of CBMC. Moreover, the response to PGE2 as well as to other cAMP-elevating agents such as forskolin and salbutamol was observed under conditions that were not associated with mast cell degranulation. CBMC expressed substantial levels of the EP2 receptor, but not the EP4 receptor, when examined by flow cytometry. In contrast to other reported PGE2-mediated effects on mast cells, VEGF-A121/165 production occurred via activation of the EP2 receptor. These data suggest a role for human mast cells as a potent source of VEGF121/165 in the absence of degranulation, and may provide new opportunities to regulate angiogenesis at mast cell-rich sites.
CXCR2−/− Mice Show Enhanced Susceptibility to Herpetic Stromal Keratitis: A Role for IL-6-Induced Neovascularization
Authors: Banerjee Kaustuv , Biswas Partha S. , Kim Bumseok , Lee Sujin , Rouse Barry T.
Published: April 2014

Ocular infection with HSV results in a blinding immunoinflammatory lesion known as herpetic stromal keratitis (HSK). Early preclinical events include inflammatory cell, mainly neutrophils, infiltration of the stroma, and neovascularization. To further evaluate the role of neutrophils in pathogenesis, HSV infection was compared in BALB/c and mice of the same background, but lacking CXCR2, the receptor for chemokines involved in neutrophil recruitment. Our results show clear differences in the outcome of ocular HSV infection in CXCR2−/− compared with control BALB/c mice. Thus, CXCR2−/− animals had minimal PMN influx during the first 7 days postinfection, and this correlated with a longer duration of virus infection in the eye compared with BALB/c mice. The CXCR2−/− mice were also more susceptible to HSV-induced lesions and developed HSK upon exposure to a dose of HSV that was minimally pathogenic to BALB/c mice. The basis for the greater HSK lesion susceptibility of CXCR2−/− mice was associated with an elevated IL-6 response, which appeared in turn to induce the angiogenic factor, vascular endothelial growth factor. Our results serve to further demonstrate the critical role of angiogenesis in the pathogenesis of ocular lesions.
Defective Control of Latent Epstein-Barr Virus Infection in Systemic Lupus Erythematosus
Authors: Kang Insoo , Quan Timothy , Nolasco Helena , Park Sung-Hwan , Hong Myung Sun , Crouch Jill , Pamer Eric G. , Howe John Greg , Craft Joe
Published: April 2014

EBV infection is more common in patients with systemic lupus erythematosus (SLE) than in control subjects, suggesting that this virus plays an etiologic role in disease and/or that patients with lupus have impaired EBV-specific immune responses. In the current report we assessed immune responsiveness to EBV in patients with SLE and healthy controls, determining virus-specific T cell responses and EBV viral loads using whole blood recall assays, HLA-A2 tetramers, and real-time quantitative PCR. Patients with SLE had an ∼40-fold increase in EBV viral loads compared with controls, a finding not explained by disease activity or immunosuppressive medications. The frequency of EBV-specific CD69+ CD4+ T cells producing IFN-γ was higher in patients with SLE than in controls. By contrast, the frequency of EBV-specific CD69+ CD8+ T cells producing IFN-γ in patients with SLE appeared lower than that in healthy controls, although this difference was not statistically significant. These findings suggest a role for CD4+ T cells in controlling, and a possible defect in CD8+ T cells in regulating, increased viral loads in lupus. These ideas were supported by correlations between viral loads and EBV-specific T cell responses in lupus patients. EBV viral loads were inversely correlated with the frequency of EBV-specific CD69+ CD4+ T cells producing IFN-γ and were positively correlated with the frequencies of CD69+ CD8+ T cells producing IFN-γ and with EBV-specific, HLA-A2 tetramer-positive CD8+ T cells. These results demonstrate that patients with SLE have defective control of latent EBV infection that probably stems from altered T cell responses against EBV.
Periportal Fibrosis in Human Schistosoma mansoni Infection Is Associated with Low IL-10, Low IFN-γ, High TNF-α, or Low RANTES, Depending on Age and Gender
Authors: Booth Mark , Mwatha Joseph K. , Joseph Sarah , Jones Frances M. , Kadzo Hilda , Ireri Edmund , Kazibwe Frances , Kemijumbi Jovanice , Kariuki Curtis , Kimani Gachuhi , Ouma John H. , Kabatereine Narcis B. , Vennervald Birgitte J. , Dunne David W.
Published: April 2014

Schistosoma mansoni infection is highly endemic in parts of Uganda, and periportal fibrosis is common in communities along the shore of Lake Albert. In this study, we have identified cellular immune responses associated with fibrosis. A cohort of 199 individuals aged 6–50, resident in the village for at least 10 years or since birth, were examined for evidence of periportal fibrosis by ultrasound using the Niamey protocol. Whole-blood samples were assayed for levels of nine cellular immune molecules (IL-3, IL-4, IL-5, IL-10, IL-13, TNF-α, IFN-γ, IL-1β, and RANTES) in the absence of in vitro Ag stimulation, and after stimulation with egg and worm Ags. A lack of Ag specificity allowed the number of variables in the analysis to be reduced by factor analysis. The resulting factor scores were then entered into a risk analysis using a classification tree algorithm. Children, adult males, and adult females had different factors associated with fibrosis. Most cases of fibrosis in children (eight of nine) were associated with low (<47th percentile) IL-10 factor scores. Adult females at lowest risk had relatively high IFN-γ factor scores (>83rd percentile), whereas those at highest risk had a combination of intermediate (32nd to 83rd percentile) IFN-γ and relatively high (>60th percentile) TNF-α factor scores. Adult males at lowest risk of fibrosis had moderate TNF-α factor scores (55th to 82nd percentile), and a high risk was associated with either high TNF-α factor scores (>82nd percentile), or intermediate TNF-α combined with low RANTES factor scores (<58th percentile). These results demonstrate that periportal fibrosis is associated with cytokine production profiles that vary with both age and gender.
Cutting Edge: BAFF Regulates CD21/35 and CD23 Expression Independent of Its B Cell Survival Function
Authors: Gorelik Leonid , Cutler Anne H. , Thill Greg , Miklasz Steven D. , Shea Dianna E. , Ambrose Christine , Bixler Sarah A. , Su Lihe , Scott Martin L. , Kalled Susan L.
Published: April 2014

Herein we demonstrate that B cell-activating factor of the TNF family (BAFF), a B cell survival factor, also regulates CD21/35 and CD23 expression. BAFF blockade in wild-type mice down-modulates CD21/35 and CD23 on B cells while survival remains intact, and BAFF exposure causes elevated CD21/35 and CD23 expression. Similar down-modulation is observed in bcl-2-transgenic mice treated with a BAFF inhibitor. This is the first evidence that BAFF has a function independent of B cell survival. Reports using CD21/35 and CD23 expression to assess splenic B cell subsets in BAFF-null mice concluded a lack of B cells beyond the immature stage. Since CD21/35 and CD23 are inadequate for delineating B cell subpopulations in BAFF-null mice, we used expression of BAFF-R and several B cell markers to identify more mature splenic B cells in these mice. These data broaden our understanding of BAFF function and correct the view that BAFF-null mice lack mature B cells.
TNF Deficiency Fails to Protect BAFF Transgenic Mice against Autoimmunity and Reveals a Predisposition to B Cell Lymphoma
Authors: Batten Marcel , Fletcher Carrie , Ng Lai Guan , Groom Joanna , Wheway Julie , Laâbi Yacine , Xin Xiaoguan , Schneider Pascal , Tschopp Jurg , Mackay Charles R. , Mackay Fabienne
Published: April 2014

TNF is well characterized as a mediator of inflammatory responses. TNF also facilitates organization of secondary lymphoid organs, particularly B cell follicles and germinal centers, a hallmark of T-dependent Ab responses. TNF also mediates defense against tumors. We examined the role of TNF in the development of inflammatory autoimmune disorders resembling systemic lupus erythematosus and Sjögren’s syndrome induced by excess B cell-activating factor belonging to the TNF family (BAFF), by generating BAFF-transgenic (Tg) mice lacking TNF. TNF−/− BAFF-Tg mice resembled TNF−/− mice, in that they lacked B cell follicles, follicular dendritic cells, and germinal centers, and have impaired responses to T-dependent Ags. Nevertheless, TNF−/− BAFF-Tg mice developed autoimmune disorders similar to that of BAFF-Tg mice. Disease in TNF−/− BAFF-Tg mice correlates with the expansion of transitional type 2 and marginal zone B cell populations and enhanced T-independent immune responses. TNF deficiency in BAFF-Tg mice also led to a surprisingly high incidence of B cell lymphomas (>35%), which most likely resulted from the combined effects of BAFF promotion of neoplastic B cell survival, coupled with lack of protective antitumor defense by TNF. Thus, TNF appears to be dispensable for BAFF-mediated autoimmune disorders and may, in fact, counter any proneoplastic effects of high levels of BAFF in diseases such as Sjögren’s syndrome, systemic lupus erythematosus, and rheumatoid arthritis.
Central Tolerance to Self-Antigen Expressed by Cortical Epithelial Cells
Authors: Mayerova Dita , Hogquist Kristin A.
Published: April 2014

The exposure of developing thymocytes to high-affinity self-Ag results in T cell tolerance. A predominant mechanism for this is clonal deletion; though receptor editing, anergy induction, and positive selection of regulatory T cells have also been described. It is unclear what signals are involved in determining different tolerance mechanisms. In particular, OT-I mice displayed receptor editing when the high-affinity self-Ag was expressed in cortical epithelial cells (cEC) using the human keratin 14 promoter. To test the hypothesis that receptor editing is a consequence of a unique instruction given by cEC presenting self-Ag, we created mice expressing the 2C and HY ligands under control of the keratin 14 promoter. Alternatively, we studied the fate of developing T cells in OT-I mice where Ag was presented by all thymic APC. Surprisingly, we found that the tolerance mechanism was not influenced by the APC subset involved in presentation. Clonal deletion was observed in 2C and HY models even when Ag was presented only by cEC; and receptor editing was observed in OT-I mice even when Ag was presented by all thymic APC. These results suggest that different TCRs show intrinsic differences in thymic tolerance mechanism.
Turnover and Proliferation of NK Cells in Steady State and Lymphopenic Conditions
Authors: Jamieson Amanda M. , Isnard Patricia , Dorfman Jeffrey R. , Coles Mark C. , Raulet David H.
Published: April 2014

To gain insight into NK cell dynamics, we investigated the turnover and proliferation rates of NK cells in normal and lymphopenic conditions. In contrast to previous reports suggesting a very rapid turnover of NK cells, continuous 5-bromo-2′-deoxyuridine (BrdU)-labeling studies demonstrated that the time necessary for labeling 50% of splenic NK cells in mature mice was 17 days, similar to the rate of labeling of memory T cells. In contrast, in young mice, splenic NK cells labeled very rapidly with BrdU, although cell cycle analyses and BrdU pulse-labeling studies suggested that most of this proliferation occurred in a precursor population. A somewhat larger percentage of bone marrow NK cells was cycling, suggesting that these proliferating cells are the precursors of the mostly nondividing or slowly dividing splenic NK cells. Splenic NK cells from mature mice also did not proliferate significantly when transferred to normal mice, but did proliferate when transferred to irradiated mice. Thus, NK cells, like T cells, undergo homeostatic proliferation in a lymphopenic environment. Homeostatic proliferation of NK cells was not dependent on host cell class I molecules or host production of IL-15. Nevertheless, the number of recovered NK cells was much lower in IL-15−/− hosts. These results suggest that IL-15 is not essential for homeostatic proliferation of NK cells, but is necessary for survival of the NK cells. Our results provide important basic information concerning the production and replacement of NK cells.
An Altered Self-Peptide with Superagonist Activity Blocks a CD8-Mediated Mouse Model of Type 1 Diabetes
Authors: Hartemann-Heurtier Agnès , Mars Lennart T. , Bercovici Nadège , Desbois Sabine , Cambouris Christophe , Piaggio Eliane , Zappulla Jacques , Saoudi Abdelhadi , Liblau Roland S.
Published: April 2014

T cell tolerance can be experimentally induced through administration of self-peptides with single amino acid substitution (altered peptide ligands or APLs). However, little is known about the effects of APLs on already differentiated autoreactive CD8+ T cells that play a pivotal role in the pathogenesis of autoimmune diabetes. We generated a panel of APLs derived from an influenza virus hemagglutinin peptide exhibiting in vitro functions ranging from antagonism to superagonism on specific CD8+ T cells. A superagonist APL was further characterized for its therapeutic activity in a transgenic mouse model of type 1 diabetes. When injected i.v. 1 day after the transfer of diabetogenic hemagglutinin-specific CD8+ T cells into insulin promoter-hemagglutinin transgenic mice, the superagonist APL proved more effective than the native hemagglutinin peptide in blocking diabetes. This protective effect was associated with an inhibition of CD8+ T cell cytotoxicity in vivo and with a decreased accumulation of these cells in the pancreas, leading to a marked reduction of intrainsulitis. In conclusion, a superagonist “self-peptide” APL was more effective than the native peptide in treating a CD8+ T cell-mediated diabetes model.
Alloantigen-Induced CD25+CD4+ Regulatory T Cells Can Develop In Vivo from CD25−CD4+ Precursors in a Thymus-Independent Process
Authors: Karim Mahzuz , Kingsley Cherry I. , Bushell Andrew R. , Sawitzki Birgit S. , Wood Kathryn J.
Published: April 2014

The capacity of naturally occurring autoreactive CD25+CD4+ regulatory T cells (Treg) to control immune responses both in vivo and in vitro is now well established. It has been demonstrated that these cells undergo positive selection within the thymus and appear to enter the periphery as committed CD25+CD4+ Treg. We have shown previously that CD25+CD4+ Treg with the capacity to prevent skin allograft rejection can be generated by pretreatment with donor alloantigen under the cover of anti-CD4 therapy. Here we demonstrate that this process does not require an intact thymus. Furthermore, generation of these Treg is not dependent on the expansion of CD25+CD4+ thymic emigrants, because depletion of CD25+ cells before pretreatment does not prevent Treg development, and Treg can be generated from CD25−CD4+ precursors. Taken together, these results clearly demonstrate that CD25+CD4+ Treg can be generated in the periphery from CD25−CD4+ precursors in a pathway distinct to that by which naturally occurring autoreactive CD25+CD4+ Treg develop. These observations may have important implications for the design of protocols, both experimental and clinical, for the induction of tolerance to autoantigens or alloantigens in adults with limited thymic function.
Tc1 and Tc2 Effector Cell Therapy Elicit Long-Term Tumor Immunity by Contrasting Mechanisms That Result in Complementary Endogenous Type 1 Antitumor Responses
Authors: Dobrzanski Mark J. , Reome Joyce B. , Hollenbaugh Joseph A. , Dutton Richard W.
Published: April 2014

Cytolytic CD8+ effector cells fall into two subpopulations based on cytokine secretion. Type 1 CD8+ T cells (Tc1) secrete IFN-γ, whereas type 2 CD8+ T cells (Tc2) secrete IL-4 and IL-5. Both effector cell subpopulations display predominantly perforin-dependent cytolysis in vitro. Using an OVA-transfected B16 lung metastases model, we show that adoptively transferred OVA-specific Tc1 and Tc2 cells induce considerable suppression, but not cure, of pulmonary metastases. However, long-term tumor immunity prolonged survival times indefinitely and was evident by resistance to lethal tumor rechallenge. At early stages after therapy, protection by Tc2 and Tc1 effector cells were dependent in part on effector cell-derived IL-4, IL-5, and IFN-γ, respectively. Whereas effector cell-derived perforin was not necessary. Over time the numbers of both donor cells diminished to low, yet still detectable, levels. Concomitantly, Tc1 and Tc2 effector cell therapies potentiated endogenous recipient-derived antitumor responses by inducing 1) local T cell-derived chemokines associated with type 1-like immune responses; 2) elevated levels of recipient-derived OVA tetramer-positive CD8 memory T cells that were CD44high, CD122+, and Ly6Chigh that predominantly produced IFN-γ and TNF-α; and 3) heightened numbers of activated recipient-derived Th1 and Tc1 T cell subpopulations expressing CD25+, CD69+, and CD95+ cell surface activation markers. Moreover, both Tc2 and Tc1 effector cell therapies were dependent in part on recipient-derived IFN-γ and TNF-α for long-term survival and protection. Collectively, Tc1 and Tc2 effector cell immunotherapy mediate long-term tumor immunity by different mechanisms that subsequently potentiate endogenous recipient-derived type 1 antitumor responses.
Chimeric Donor Cells Play an Active Role in Both Induction and Maintenance Phases of Transplantation Tolerance Induced by Mixed Chimerism
Authors: Kanamoto Akira , Maki Takashi
Published: April 2014

Donor hemopoietic cell engraftment is considered to be an indicator of allograft tolerance. We depleted chimerism with cells specifically presensitized to the bone marrow donor to investigate its role in mixed chimera-induced tolerance. Three experimental models were used: model A, B10.A cells presensitized to B6 (a anti-b cells) were injected into (B6 × D2)F1 → B10.A mixed chimeras grafted with DBA/2 skin; model B, anti-B6 presensitized cells prepared in DBA/2 → B10.A mixed chimeras, thus unresponsive to DBA/2 (a anti-b/tol-d cells), were injected into (B6 × D2)F1 → B10.A mixed chimeras grafted with DBA/2 skin; and model C, (BALB/c × B6)F1 cells presensitized to CBA (d/b anti-k cells) were injected into (B6 × CBA)F1 → BALB/c mixed chimeras grafted with B6 skin. Skin was grafted on day 30. Injection of each cell type before skin grafting abolished hemopoietic cell engraftment and prevented allograft acceptance. Injection of presensitized cells after skin grafting resulted in different outcomes depending on the models. In model A, injection of a anti-b cells completely depleted chimerism and caused allograft rejection. In model B, injection of a anti-b/tol-d cells markedly reduced, but did not deplete, peripheral chimerism and maintained skin allograft survival. In model C, d/b anti-k cells reduced chimerism to the background levels but failed to cause graft rejection, probably due to persistence of injected cells which share MHC with skin grafts. Together, the results show that presence of chimeric donor cells is essential in both the induction and maintenance phases of tolerance induced by mixed chimerism.
Zwitterionic Polysaccharides Stimulate T Cells with No Preferential Vβ Usage and Promote Anergy, Resulting in Protection against Experimental Abscess Formation
Authors: Stingele Francesca , Corthésy Blaise , Kusy Nicole , Porcelli Steven A. , Kasper Dennis L. , Tzianabos Arthur O.
Published: April 2014

Zwitterionic polysaccharides (Zps) from pathogenic bacteria, such as Bacteroides fragilis, are virulence factors responsible for abscess formation associated with intra-abdominal sepsis. The underlying cellular mechanism for abscess formation requires T cell activation. Conversely, abscess formation can be prevented by prophylactic s.c. injection of purified Zps alone, a process also dependent on T cells. Hence, the modulatory role of T cells in abscess formation was investigated. We show that Zps interact directly with T cells with fast association/dissociation kinetics. Vβ repertoire analysis using RT-PCR demonstrates that Zps have broad Vβ usage. Zps-specific hybridomas responded to a variety of other Zps, but not to a nonzwitterionic polysaccharide, indicating cross-reactivity between different Zps. Furthermore, Zps-reactive T cell hybridomas could effectively transfer protection against abscess formation. Analysis of the proliferative capacity of T cells recovered from Zps-treated animals revealed that these T cells are anergic to subsequent stimulation by the different Zps or to alloantigens in an MLR. This anergic response was relieved by addition of IL-2. Taken together, the data show that this class of polysaccharides interacts directly with T cells in a nonbiased manner to elicit an IL-2-dependent anergic response that confers protection against abscess formation.
Effect of Chronic Viral Infection on Epitope Selection, Cytokine Production, and Surface Phenotype of CD8 T Cells and the Role of IFN-γ Receptor in Immune Regulation
Authors: Tewari Kavita , Sacha Jonah , Gao Xiaoyan , Suresh M.
Published: April 2014

Regulation of CD8 T cell responses in chronic viral infections is not well understood. In this study, we have compared the CD8 T cell responses to immunodominant and subdominant epitopes during an acute and a chronic lymphocytic choriomeningitis virus (LCMV) infection in mice. The epitope hierarchy of the primary CD8 T cell response was similar in acute and chronic LCMV infections. However, strikingly, the epitope hierarchy of the primary CD8 T cell response was conserved in the T cell memory only in an acute but not in a chronic LCMV infection. Interestingly, in an acute infection, increasing the viral dose caused significant changes in the epitope hierarchy of the LCMV-specific memory CD8 T cell pool, with no effect on the primary CD8 T cell response. Functional and phenotypic analyses revealed that exposure of CD8 T cells to extended periods of antigenic stimulation could lead to long-term defects in cytokine production and alteration in expression of cell surface L-selectin (CD62L). Whereas expression of CD44 was minimally altered, a greater proportion of LCMV-specific memory CD8 T cells were CD62Llow in mice that have recovered from a chronic LCMV infection, compared with acutely infected mice. Mechanistic studies showed that IFN-γR deficiency altered the epitope hierarchy of the pool of LCMV-specific memory CD8 T cells without significantly affecting the immunodominance of the primary CD8 T cell response in an acute infection. Taken together, these findings should further our understanding about the regulation of T cell responses in human chronic viral infections.
Expression of Dual TCR on DO11.10 T Cells Allows for Ovalbumin-Induced Oral Tolerance to Prevent T Cell-Mediated Colitis Directed against Unrelated Enteric Bacterial Antigens
Authors: Zhou Pengfei , Borojevic Rajka , Streutker Cathy , Snider Denis , Liang Hong , Croitoru Kenneth
Published: April 2014

The triggering Ag for inflammatory bowel disease and animal models of colitis is not known, but may include gut flora. Feeding OVA to DO11.10 mice with OVA-specific transgenic (Tg) TCR generates Ag-specific immunoregulatory CD4+ T cells (Treg) cells. We examined the ability of oral Ag-induced Treg cells to suppress T cell-mediated colitis in mice. SCID-bg mice given DO11.10 CD4+CD45RBhigh T cells developed colitis, and cotransferring DO11.10 CD45RBlowCD4+ T cells prevented CD4+CD45RBhigh T cell-induced colitis in the absence of OVA. The induction and prevention of disease by DO11.10 CD4+ T cell subsets were associated with an increase in endogenous TCRα chain expression on Tg T cells. Feeding OVA to SCID-bg mice reconstituted with DO11.10 CD4+CD45RBhigh attenuated the colitis in association with increased TGF-β and IL-10 secretion, and decreased proliferative responses to both OVA and cecal bacteria Ag. OVA feeding also attenuated colitis in SCID-bg mice reconstituted with a mix of BALB/c and DO11.10 CD45RBhigh T cells, suggesting that OVA-induced Treg cells suppressed BALB/c effector cells. The expression of endogenous non-Tg TCR allowed for DO11.10-derived T cells to respond to enteric flora Ag. Furthermore, feeding OVA-induced Treg cells prevented colitis by inducing tolerance in both OVA-reactive and non-OVA-reactive T cells and by inducing Ag-nonspecific Treg cells. Such a mechanism might allow for Ag-nonspecific modulation of intestinal inflammation in inflammatory bowel disease.
Deceptive Multilineage Reconstitution Analysis of Mice Transplanted with Hemopoietic Stem Cells, and Implications for Assessment of Stem Cell Numbers and Lineage Potentials
Authors: Bryder David , Sasaki Yutaka , Borge Ole Johan , Jacobsen Sten-Eirik W.
Published: April 2014

Hemopoietic stem cells (HSC) are identified through their unique ability, at the single cell level, to long-term reconstitute all blood cell lineages. Sustained myeloid reconstitution is considered the hallmark of HSC, because myeloid progenitors and their progeny have very short half-lives. Here we demonstrate that the established practice of relying on RB6-8C5 as a myeloid specific Ab can result in overestimation of HSC frequencies because the RB6-8C5 Ab also detects Ags expressed on a sizeable population of CD3+CD8+ T cells, constitutively as well as following transplantation. Likewise, a high fraction of mice transplanted with limiting numbers of ex vivo expanded Lin−Sca+kit+CD34− HSC show long-term RB6-8C5+CD3+ (lymphoid) but no RB6-8C5+CD3− (myeloid) reconstitution. Most noteworthy, the use of RB6-8C5 as a myeloid specific Ab can be deceptive by implicating the existence of lineage-restricted HSC capable of long-term reconstituting the myeloid and T, but not B, cell lineage. Because cross-lineage expression of “lineage-specific” markers is unlikely to be unique to the blood system, claims of unexpected cell fates should be substantiated not only by acquisition of lineage-specific markers, but also absence of markers of other lineages normally derived from the investigated stem cells.
Intravenous Injection of a Lentiviral Vector Encoding NY-ESO-1 Induces an Effective CTL Response
Authors: Palmowski Michael J. , Lopes Luciene , Ikeda Yasuhiro , Salio Mariolina , Cerundolo Vincenzo , Collins Mary K.
Published: April 2014

Lentiviral vectors can efficiently transduce a variety of nondividing cells, including APCs. We assessed the immunogenicity of a lentiviral vector encoding the melanoma Ag NY-ESO-1 in HLA-A2 transgenic mice. Direct i.v. injection of NY-ESO-1 lentivirus induced NY-ESO-1157–165-specific CD8+ cells, detected ex vivo with an A2/H-2Kb chimeric class I tetramer. These NY-ESO-1157–165-specific CD8+ cells could be expanded by boosting with an NY-ESO-1 vaccinia virus and could kill NY-ESO-1157–165 peptide-pulsed targets in vivo. Such direct lentiviral vector injection was similar in potency to the injection of in vitro-transduced dendritic cells (DC). In addition, human monocyte-derived DC transduced by the NY-ESO-1 lentivirus stimulated an NY-ESO-1157–165-specific specific CTL clone. These data suggest that direct lentiviral transduction of DC in vivo might provide a powerful immunotherapeutic strategy.
Ontogeny of γδ T Cells in Humans
Authors: De Rosa Stephen C. , Andrus James P. , Perfetto Stephen P. , Mantovani John J. , Herzenberg Leonard A. , Herzenberg Leonore A. , Roederer Mario
Published: April 2014

T cell receptors consist either of an α-chain combined with a β-chain or a γ-chain combined with a δ-chain. αβ T cells constitute the majority of T cells in human blood throughout life. Flow cytometric analyses presented in this study, which focus on the representation of the developmental (naive and memory) subsets of γδ T cells, show by function and phenotype that this lineage contains both naive and memory cells. In addition, we show that the representation of naive T cells is higher among αβ than γδ T cells in adults and that the low frequency of naive γδ T cells in adults reflects ontological differences between the two major γδ subsets, which are distinguished by expression of Vδ1 vs Vδ2 δ-chains. Vδ1 cells, which mirror αβ cells with respect to naive representation, predominate during fetal and early life, but represent the minority of γδ cells in healthy adults. In contrast, Vδ2 cells, which constitute the majority of adult γδ cells, show lower frequencies of naive cells than Vδ1 early in life and show vanishingly small naive frequencies in adults. In essence, nearly all naive Vδ2 cells disappear from blood by 1 year of life. Importantly, even in children less than 1 year old, most of the nonnaive Vδ2 cells stain for perforin and produce IFN-γ after short-term in vitro stimulation. This represents the earliest immunological maturation of any lymphocyte compartment in humans and most likely indicates the importance of these cells in controlling pathology due to common environmental challenges.
Critical Role of OX40 in CD28 and CD154-Independent Rejection
Authors: Demirci Gülçin , Amanullah Farhana , Kewalaramani Reshma , Yagita Hideo , Strom Terry B. , Sayegh Mohamed H. , Li Xian Chang
Published: April 2014

Blocking both CD28 and CD154 costimulatory pathways can induce transplant tolerance in some, but not all, transplant models. Under stringent conditions, however, this protocol often completely fails to block allograft rejection. The precise nature of such CD28/CD154 blockade-resistant rejection is largely unknown. In the present study we developed a new model in which both CD28 and CD154, two conventional T cell costimulatory molecules, are genetically knocked out (i.e., CD28/CD154 double-knockout (DKO) mice) and used this model to examine the role of novel costimulatory molecule-inducible costimulator (ICOS), OX40, 4-1BB, and CD27 in mediating CD28/CD154-independent rejection. We found that CD28/CD154 DKO mice vigorously rejected fully MHC-mismatched DBA/2 skin allografts (mean survival time, 12 days; n = 6) compared with the wild-type controls (mean survival time, 8 days; n = 7). OX40 costimulation is critically important in skin allograft rejection in this model, as blocking the OX40/OX40 ligand pathway, but not the ICOS/ICOS ligand, 4-1BB/4-1BBL, or CD27/CD70 pathway, markedly prolonged skin allograft survival in CD28/CD154 DKO mice. The critical role of OX40 costimulation in CD28/CD154-independent rejection is further confirmed in wild-type C57BL/6 mice, as blocking the OX40/OX40 ligand pathway in combination with CD28/CD154 blockade induced long term skin allograft survival (>100 days; n = 5). Our study revealed a key cellular mechanism of rejection and identified OX40 as a critical alternative costimulatory molecule in CD28/CD154-independent rejection.
IFN-α Sensitizes Human Umbilical Vein Endothelial Cells to Apoptosis Induced by Double-Stranded RNA
Authors: Kaiser William J. , Kaufman Jonathan L. , Offermann Margaret K.
Published: April 2014

The ability of endothelial cells to mount an efficient antiviral response is important in restricting viral dissemination and eliminating viral infection from the endothelium and surrounding tissues. We demonstrate that dsRNA, a molecular signature of viral infection, induced apoptosis in HUVEC, and priming with IFN-α shortened the time between when dsRNA was encountered and when apoptosis was initiated. IFN-α priming induced higher levels of mRNA for dsRNA-activated protein kinase, 2′5′-oligoadenylate synthetase, and Toll-like receptor 3, transcripts that encode dsRNA-responsive proteins. dsRNA induced activation of dsRNA-activated protein kinase and nuclear translocation of transcription factors RelA and IFN regulatory factor-3 in IFN-α-primed HUVECs before the activation of intrinsic and extrinsic apoptotic pathways. These changes did not occur in the absence of dsRNA, and apoptosis resulting from incubation with dsRNA occurred much later when cells were not primed with IFN-α. The entire population of IFN-α-primed HUVECs underwent nuclear translocation of RelA and IFN regulatory factor-3 in response to dsRNA, whereas less than one-half of the population responded with apoptosis. When IFN-α-primed HUVECs were coincubated with dsRNA and proteasome inhibitors, all HUVECs were rendered susceptible to dsRNA-induced apoptosis. These studies provide evidence that many endothelial cells that are alerted to the risk of infection by IFN-α would undergo apoptosis sooner in response to dsRNA than non-IFN-α-primed cells, and this would enhance the likelihood of eliminating infected cells prior to the production of progeny virions.
Impaired Production of Proinflammatory Cytokines and Host Resistance to Acute Infection withTrypanosoma cruziin Mice Lacking Functional Myeloid Differentiation Factor 88
Authors: Campos Marco A. , Closel Meire , Valente Eneida P. , Cardoso Jarbas E. , Akira Shizuo , Alvarez-Leite Jacqueline I. , Ropert Catherine , Gazzinelli Ricardo T.
Published: April 2014

Studies performed in vitro suggest that activation of Toll-like receptors (TLRs) by parasite-derived molecules may initiate inflammatory responses and host innate defense mechanisms against Trypanosoma cruzi. Here, we evaluated the impact of TLR2 and myeloid differentiation factor 88 (MyD88) deficiencies in host resistance to infection with T. cruzi. Our results show that macrophages derived from TLR2 −/− and MyD88−/− mice are less responsive to GPI-mucin derived from T. cruzi trypomastigotes and parasites. In contrast, the same cells from TLR2−/− still produce TNF-α, IL-12, and reactive nitrogen intermediates (RNI) upon exposure to live T. cruzi trypomastigotes. Consistently, we show that TLR2−/− mice mount a robust proinflammatory cytokine response as well as RNI production during the acute phase of infection with T. cruzi parasites. Further, deletion of the functional TLR2 gene had no major impact on parasitemia nor on mortality. In contrast, the MyD88−/− mice had a diminished cytokine response and RNI production upon acute infection with T. cruzi. More importantly, we show that MyD88−/− mice are more susceptible to infection with T. cruzi as indicated by the higher parasitemia and accelerated mortality, as compared with the wild-type mice. Together, our results indicate that T. cruzi parasites elicit an alternative inflammatory pathway independent of TLR2. This pathway is partially dependent on MyD88 and necessary for mounting optimal inflammatory and RNI responses that control T. cruzi replication during the early stages of infection.
Dendritic Cells Pulsed with Live and DeadLegionella pneumophilaElicit Distinct Immune Responses
Authors: Kikuchi Toshiaki , Kobayashi Takao , Gomi Kazunori , Suzuki Takuji , Tokue Yutaka , Watanabe Akira , Nukiwa Toshihiro
Published: April 2014

Legionella pneumophila is the causative pathogen of Legionnaires’ disease, which is characterized by severe pneumonia. In regard to the pathophysiology of Legionella infection, the role of inflammatory phagocytes such as macrophages has been well documented, but the involvement of dendritic cells (DCs) has not been clarified. In this study, we have investigated the immune responses that DCs generate in vitro and in vivo after contact with L. pneumophila. Heat- and formalin-killed L. pneumophila, but not live L. pneumophila, induced immature DCs to undergo similar phenotypic maturation, but the secreted proinflammatory cytokines showed different patterns. The mechanisms of the DC maturation by heat- or formalin-killed L. pneumophila depended, at least in part, on Toll-like receptor 4 signaling or on Legionella LPS, respectively. After transfer to naive mice, DCs pulsed with dead Legionella produced serum Ig isotype responses specific for Legionella, leading to protective immunity against an otherwise lethal respiratory challenge with L. pneumophila. The in vivo immune responses required the Ag presentation of DCs, especially that on MHC class II molecules, and the immunity yielded cross-protection between clinical and environmental strains of L. pneumophila. Although the DC maturation was impaired by live Legionella, macrophages were activated by live as well as dead L. pneumophila, as evidenced by the up-regulation of MHC class II. Finally, DCs, but not macrophages, exhibited a proliferative response to live L. pneumophila that was consistent with their cell cycle progression. These findings provide a better understanding of the role of DCs in adaptive immunity to Legionella infection.
Human T Cell Lymphotropic Virus Type I (HTLV-I)-Specific CD4+ T Cells: Immunodominance Hierarchy and Preferential Infection with HTLV-I
Authors: Goon Peter K. C. , Igakura Tadahiko , Hanon Emmanuel , Mosley Angelina J. , Barfield Anna , Barnard Amanda L. , Kaftantzi Lambrini , Tanaka Yuetsu , Taylor Graham P. , Weber Jonathan N. , Bangham Charles R. M.
Published: April 2014

CD4+ T cells predominate in early lesions in the CNS in the inflammatory disease human lymphotropic T cell virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP), but the pathogenesis of the disease remains unclear and the HTLV-I-specific CD4+ T cell response has been little studied. We quantified the IFN-γ-producing HTLV-I-specific CD4+ T cells, in patients with HAM/TSP and in asymptomatic carriers with high proviral load, to test two hypotheses: that HAM/TSP patients and asymptomatic HTLV-I carriers with a similar proviral load differ in the immunodominance hierarchy or the total frequency of specific CD4+ T cells, and that HTLV-I-specific CD4+ T cells are preferentially infected with HTLV-I. The strongest CD4+ T cell response in both HAM/TSP patients and asymptomatic carriers was specific to Env. This contrasts with the immunodominance of Tax in the HTLV-I-specific CD8+ T cell response. The median frequency of HTLV-I-specific IFN-γ+ CD4+ T cells was 25-fold greater in patients with HAM/TSP (p = 0.0023, Mann-Whitney) than in asymptomatic HTLV-I carriers with a similar proviral load. Furthermore, the frequency of CD4+ T cells infected with HTLV-I (expressing Tax protein) was significantly greater (p = 0.0152, Mann-Whitney) among HTLV-I-specific cells than CMV-specific cells. These data were confirmed by quantitative PCR for HTLV-I DNA. We conclude that the high frequency of specific CD4+ T cells was associated with the disease HAM/TSP, and did not simply reflect the higher proviral load that is usually found in HAM/TSP patients. Finally, we conclude that HTLV-I-specific CD4+ T cells are preferentially infected with HTLV-I.