bluuebunny/crossref_metadata_2025 huggingface dataset:
Mutation in the Fas Pathway Impairs CD8+ T Cell Memory
Authors: Dudani Renu , Russell Marsha , van Faassen Henk , Krishnan Lakshmi , Sad Subash
Published: April 2014

Fas death pathway is important for lymphocyte homeostasis, but the role of Fas pathway in T cell memory development is not clear. We show that whereas the expansion and contraction of CD8+ T cell response against Listeria monocytogenes were similar for wild-type (WT) and Fas ligand (FasL) mutant mice, the majority of memory CD8+ T cells in FasL mutant mice displayed an effector memory phenotype in the long-term in comparison with the mainly central memory phenotype displayed by memory CD8+ T cells in WT mice. Memory CD8+ T cells in FasL mutant mice expressed reduced levels of IFN-γ and displayed poor homeostatic and Ag-induced proliferation. Impairment in CD8+ T cell memory in FasL mutant hosts was not due to defective programming or the expression of mutant FasL on CD8+ T cells, but was caused by perturbed cytokine environment in FasL mutant mice. Although adoptively transferred WT memory CD8+ T cells mediated protection against L. monocytogenes in either the WT or FasL mutant hosts, FasL mutant memory CD8+ T cells failed to mediate protection even in WT hosts. Thus, in individuals with mutation in Fas pathway, impairment in the function of the memory CD8+ T cells may increase their susceptibility to recurrent/latent infections.
Involvement of Secretory and Endosomal Compartments in Presentation of an Exogenous Self-Glycolipid to Type II NKT Cells
Authors: Roy Keshab Chandra , Maricic Igor , Khurana Archana , Smith Trevor R. F. , Halder Ramesh C. , Kumar Vipin
Published: April 2014

Natural Killer T (NKT) cells recognize both self and foreign lipid Ags presented by CD1 molecules. Although presentation of the marine sponge-derived lipid αGalCer to type I NKT cells has been well studied, little is known about self-glycolipid presentation to either type I or type II NKT cells. Here we have investigated presentation of the self-glycolipid sulfatide to a type II NKT cell that specifically recognizes a single species of sulfatide, namely lyso-sulfatide but not other sulfatides containing additional acyl chains. In comparison to other sulfatides or αGalCer, lyso-sulfatide binds with lower affinity to CD1d. Although plate-bound CD1d is inefficient in presenting lyso-sulfatide at neutral pH, it is efficiently presented at acidic pH and in the presence of saposin C. The lysosomal trafficking of mCD1d is required for αGalCer presentation to type I NKT cells, it is not important for presentation of lyso-sulfatide to type II NKT cells. Consistently, APCs deficient in a lysosomal lipid-transfer protein effectively present lyso-sulfatide. Presentation of lyso-sulfatide is inhibited in the presence of primaquine, concanamycin A, monensin, cycloheximide, and an inhibitor of microsomal triglyceride transfer protein but remains unchanged following treatment with brefeldin A. Wortmannin-mediated inhibition of lipid presentation indicates an important role for the PI-3kinase in mCD1d trafficking. Our data collectively suggest that weak CD1d-binding self-glycolipid ligands such as lyso-sulfatide can be presented via the secretory and endosomal compartments. Thus this study provides important insights into the exogenous self-glycolipid presentation to CD1d-restricted T cells.
Splenic Stromal Microenvironment Negatively Regulates Virus-Activated Plasmacytoid Dendritic Cells through TGF-β
Authors: Li Li , Liu Shuxun , Zhang Ting , Pan Wei , Yang Xiao , Cao Xuetao
Published: April 2014

Plasmacytoid dendritic cells (pDCs) secrete large amounts of IFN-α upon exposure to virus, subsequently promoting and regulating innate and adaptive immune responses. However, little is known about the functional regulation of virus-activated pDCs after they exert functions in secondary lymph organs. Our previous studies show that splenic stromal microenvironment can down-regulate the T cell response by inducing generation of regulatory myeloid dendritic cells; therefore, we wondered whether the splenic stromal microenvironment can regulate the function of virus-activated pDCs. In this study, we provide evidences that the splenic stromal microenvironment can chemoattract vesicular stomatitis virus (VSV)-activated pDCs via stromal cell-derived dactor 1 (SDF-1), inhibit the secretion of IFN-α, IL-12, TNF-α, and expression of I-Ab, CD86, CD80, and CD40 by VSV-activated pDCs, and subsequently inhibit VSV-infected pDCs to activate NK cell IFN-γ production and cytotoxicity. Stroma-derived TGF-β participates in the negative regulation of VSV-activated pDCs. Therefore, we demonstrate that splenic stromal microenvironment negatively regulates the virus-activated pDCs through TGF-β, outlining an additional mechanistic explanation for maintenance of immune homeostasis.
Proliferative Expansion and Acquisition of Effector Activity by Memory CD4+ T Cells in the Lungs following Pulmonary Virus Infection
Authors: Wissinger Erika L. , Stevens Whitney W. , Varga Steven M. , Braciale Thomas J.
Published: April 2014

The memory CD4+ T cell response to the respiratory syncytial virus (RSV) attachment (G) protein in the lungs of primed BALB/c mice undergoing challenge pulmonary RSV infection is dominated by effector T cells expressing a single Vβ-chain, Vβ14. We have used Vβ14 expression to examine the kinetics of the activation, accumulation, and acquisition of the effector activity of memory CD4+ T cells responding to pulmonary infection. This analysis revealed that proliferative expansion and effector CD4+ T cell differentiation preferentially occur in the respiratory tract following rapid activation within and egress from the lymph nodes draining the respiratory tract. These findings suggest that, in response to natural infection at a peripheral mucosal site such as the lungs, memory CD4+ T cell expansion and differentiation into activated effector T cells may occur predominantly in the peripheral site of infection rather than exclusively in the lymph nodes draining the site of infection.
Expression of ICOS on Human Melanoma-Infiltrating CD4+CD25highFoxp3+ T Regulatory Cells: Implications and Impact on Tumor-Mediated Immune Suppression
Authors: Strauss Laura , Bergmann Christoph , Szczepanski Miroslaw J. , Lang Stephan , Kirkwood John M. , Whiteside Theresa L.
Published: April 2014

Objective: Interaction of ICOS with its ligand (ICOSL, B7-H2) promotes T cell responses. As CD4+CD25highFoxp3+ naturally occurring T regulatory cells in melanoma patients express ICOS, we investigated the impact of ICOS on naturally occurring T regulatory cell function. Methods: Expression of ICOS and T regulatory (Treg) cell markers was determined on CD4+CD25high T cells in PBMC and tumor-infiltrating lymphocytes from melanoma patients (n = 10) and PBMC of normal controls (n = 10) by multicolor flow cytometry. Suppression mediated by sorted ICOShigh and ICOSlow Treg was assessed in CFSE-based suppression assays with autologous CD4+CD25− responder cells (RC). Transwell inserts separating Treg from RC were used to evaluate suppression mechanisms used by Treg. ICOShigh or ICOSlow Treg were coincubated with RC ± TCR and IL-2 stimulation. ICOShigh and ICOS− Treg were also expanded under conditions previously shown to induce Tr1 from RC. Results: Treg in tumor-infiltrating lymphocytes expressed ICOS (mean fluorescence intensity = 70 ± 10), while Treg in PBMC had low ICOS expression (mean fluorescence intensity = 3.5 ± 2.5, p ≤ 0.001). ICOShigh Treg up-regulated Treg markers (p ≤ 0.0016) and mediated stronger suppression (p ≤ 0.001) relative to ICOSlow Treg. ICOShigh Treg induced Tr1 cells in nonactivated RC and Th2 cells in preactivated RC. ICOShigh Treg exposed to Tr1 cytokines expressed IL-10 and suppressed RC (92 ± 12%) in contrast to ICOSlow Treg, which mediated low suppression (21 ± 15%; p ≤ 0.0028). Conclusion: ICOShigh Treg can induce diverse immune responses in RC, depending on activation signals and cytokines present. ICOShigh Treg induce Tr1 or Th2 cells depending on the activation state of RC. In a “Tr1” cytokine milieu, ICOShigh Treg transit to Tr1.
Regulatory and Conventional CD4+ T Cells Show Differential Effects Correlating with PD-1 and B7-H1 Expression after Immunotherapy
Authors: Alderson Kory L. , Zhou Qing , Berner Vanessa , Wilkins Danice E. C. , Weiss Jonathan M. , Blazar Bruce R. , Welniak Lisbeth A. , Wiltrout Robert H. , Redelman Doug , Murphy William J.
Published: April 2014

Recently, our laboratory reported that secondary CD8+ T cell-mediated antitumor responses were impaired following successful initial antitumor responses using various immunotherapeutic approaches. Although immunotherapy stimulated significant increases in CD8+ T cell numbers, the number of CD4+ T cells remained unchanged. The current investigation revealed a marked differential expansion of CD4+ T cell subsets. Successful immunotherapy surprisingly resulted in an expansion of CD4+Foxp3+ regulatory T (Treg) cells concurrent with a reduction of conventional CD4+ T (Tconv) cells, despite the marked antitumor responses. Following immunotherapy, we observed differential up-regulation of PD-1 on the surface of CD4+Foxp3+ Treg cells and CD4+Foxp3− Tconv cells. Interestingly, it was the ligand for PD-1, B7-H1 (PDL-1), that correlated with Tconv cell loss after treatment. Furthermore, IFN-γ knockout (IFN-γ−/−) and IFN-γ receptor knockout (IFN-γR−/−) animals lost up-regulation of surface B7-H1 even though PD-1 expression of Tconv cells was not changed, and this correlated with CD4+ Tconv cell increases. These results suggest that subset-specific expansion may contribute to marked shifts in the composition of the T cell compartment, potentially influencing the effectiveness of some immunotherapeutic approaches that rely on IFN-γ.
Rat CD4+CD8+ Macrophages Kill Tumor Cells through an NKG2D- and Granzyme/Perforin-Dependent Mechanism
Authors: Baba Tomohisa , Iwasaki Sari , Maruoka Takako , Suzuki Akira , Tomaru Utano , Ikeda Hitoshi , Yoshiki Takashi , Kasahara Masanori , Ishizu Akihiro
Published: April 2014

We previously identified a subpopulation of monocyte/macrophage lineage cells expressing both CD4 and CD8. This subpopulation was expanded in rat peripheral blood and spleen after immunization with adjuvants containing killed tuberculosis germs. CD4+CD8+ monocytes/macrophages obtained from preimmunized rats exhibited a Th1-type cytokine/chemokine profile, expressed high levels of Fas ligand, perforin, granzyme B, and NKR-P2 (rat ortholog of human NKG2D), and killed certain tumor cells. In the present study, we confirmed that CD4+CD8+ monocytes/macrophages are distinct from splenic dendritic cells (DCs) or IFN-producing killer DCs. In vitro cytotoxic assays revealed that CD4+CD8+ macrophages killed tumor cells in a cell-cell contact-dependent manner and that expression of the retinoic acid early transcript 1 (a ligand for NKG2D) made tumor cells susceptible to killing by CD4+CD8+ macrophages. Furthermore, inhibitors of granzyme and perforin significantly decreased cytotoxic activities of CD4+CD8+ macrophages. Consistent with these in vitro findings, preimmunization with adjuvants containing killed tuberculosis germs elevated the expression of granzyme B in tumor-infiltrating CD4+CD8+ macrophages and significantly inhibited the growth of inoculated tumor cells. Our current work demonstrates that CD4+CD8+ macrophages are a unique subpopulation of monocyte/macrophage lineage cells that kill tumor cells in an NKG2D- and granzyme/perforin-dependent mechanism.
Blood Monocyte Subsets Differentially Give Rise to CD103+ and CD103− Pulmonary Dendritic Cell Populations
Authors: Jakubzick Claudia , Tacke Frank , Ginhoux Florent , Wagers Amy J. , van Rooijen Nico , Mack Matthias , Merad Miriam , Randolph Gwendalyn J.
Published: April 2014

There are two major myeloid pulmonary dendritic cell (DC) populations: CD103+ DCs and CD11bhigh DCs. In this study, we investigated in detail the origins of both myeloid DC pools using multiple experimental approaches. We show that, in resting lung, Ly-6ChighCCR2high monocytes repopulated CD103+ DCs using a CCR2-dependent mechanism, and these DCs preferentially retained residual CCR2 in the lung, whereas, conversely, Ly-6ClowCCR2low monocytes repopulated CD11bhigh DCs. CX3CR1 was required to generate normal numbers of pulmonary CD11bhigh DCs, possibly because Ly-6Clow monocytes in the circulation, which normally express high levels of CX3CR1, failed to express bcl-2 and may have diminished survival in the circulation in the absence of CX3CR1. Overall, these data demonstrate that the two circulating subsets of monocytes give rise to distinct tissue DC populations.
Prophylactic Treatment with Fms-Like Tyrosine Kinase-3 Ligand after Burn Injury Enhances Global Immune Responses to Infection
Authors: Bohannon Julia , Cui Weihua , Cox Robert , Przkora Rene , Sherwood Edward , Toliver-Kinsky Tracy
Published: April 2014

Severely burned patients are susceptible to infections with opportunistic organisms due to altered immune responses and frequent wound contamination. Immunomodulation to enhance systemic and local responses to wound infections may be protective after burn injury. We previously demonstrated that pretreatments with fms-like tyrosine kinase-3 (Flt3) ligand (Flt3L), a dendritic cell growth factor, increase the resistance of mice to a subsequent burn injury and wound infection by a dendritic cell-dependent mechanism. This study was designed to test the hypothesis that Flt3L administration after burn injury decreases susceptibility to wound infections by enhancing global immune cell activation. Mice were treated with Flt3L after burn injury and examined for survival, wound and systemic bacterial clearance, and immune cell activation after wound inoculation with Pseudomonas aeruginosa. To gain insight into the local effects of Flt3L at the burn wound, localization of Langerhans cells was examined. Mice treated with Flt3L had significantly greater numbers of CD25-expressing T cells and CD69-expressing T and B cells, neutrophils, and macrophages after, but not before, infection. Overall leukocyte apoptosis in response to infection was decreased with Flt3L treatment. Survival and local and systemic bacterial clearance were enhanced by Flt3L. Langerhans cells appeared in the dermis of skin bordering the burn wound, and further increased in response to wound infection. Flt3L augmented the appearance of Langerhans cells in response to both injury and infection. These data suggest that dendritic cell enhancement by Flt3L treatments after burn injury protects against opportunistic infections through promotion of local and systemic immune responses to infection.
Dermal Dendritic Cells, and Not Langerhans Cells, Play an Essential Role in Inducing an Immune Response
Authors: Fukunaga Atsushi , Khaskhely Noor M. , Sreevidya Coimbatore S. , Byrne Scott N. , Ullrich Stephen E.
Published: April 2014

Langerhans cells (LCs) serve as epidermal sentinels of the adaptive immune system. Conventional wisdom suggests that LCs encounter Ag in the skin and then migrate to the draining lymph nodes, where the Ag is presented to T cells, thus initiating an immune response. Platelet-activating factor (PAF) is a phospholipid mediator with potent biological effects. During inflammation, PAF mediates recruitment of leukocytes to inflammatory sites. We herein tested a hypothesis that PAF induces LC migration. Applying 2,4-dinitro-1-fluorobenzene (DNFB) to wild-type mice activated LC migration. In contrast, applying DNFB to PAF receptor-deficient mice or mice injected with PAF receptor antagonists failed to induce LC migration. Moreover, after FITC application the appearance of hapten-laden LCs (FITC+, CD11c+, Langerin+) in the lymph nodes of PAF receptor-deficient mice was significantly depressed compared with that found in wild-type mice. LC chimerism indicates that the PAF receptor on keratinocytes but not LCs is responsible for LC migration. Contrary to the diminution of LC migration in PAF receptor-deficient mice, we did not observe any difference in the migration of hapten-laden dermal dendritic cells (FITC+, CD11c+, Langerin−) into the lymph nodes of PAF receptor-deficient mice. Additionally, the contact hypersensitivity response generated in wild-type or PAF receptor-deficient mice was identical. Finally, dermal dendritic cells, but not LCs isolated from the draining lymph nodes after hapten application, activated T cell proliferation. These findings suggest that LC migration may not be responsible for the generation of contact hypersensitivity and that dermal dendritic cells may play a more important role.
Exosomes As a Short-Range Mechanism to Spread Alloantigen between Dendritic Cells during T Cell Allorecognition
Authors: Montecalvo Angela , Shufesky William J. , Beer Stolz Donna , Sullivan Mara G. , Wang Zhiliang , Divito Sherrie J. , Papworth Glenn D. , Watkins Simon C. , Robbins Paul D. , Larregina Adriana T. , Morelli Adrian E.
Published: April 2014

Exosomes are nanovesicles released by different cell types including dendritic cells (DCs). The fact that exosomes express surface MHC-peptide complexes suggests that they could function as Ag-presenting vesicles or as vehicles to spread allogeneic Ags for priming of anti-donor T cells during elicitation of graft rejection or induction/maintenance of transplant tolerance. We demonstrate that circulating exosomes transporting alloantigens are captured by splenic DCs of different lineages. Internalization of host-derived exosomes transporting allopeptides by splenic DCs leads to activation of anti-donor CD4 T cells by the indirect pathway of allorecognition, a phenomenon that requires DC-derived, instead of exosome-derived, MHC class II molecules. By contrast, allogeneic exosomes are unable to stimulate direct-pathway T cells in vivo. We demonstrate in mice that although graft-infiltrating leukocytes release exosomes ex vivo, they do not secrete enough concentrations of exosomes into circulation to stimulate donor-reactive T cells in secondary lymphoid organs. Instead, our findings indicate that migrating DCs (generated in vitro or isolated from allografts), once they home in the spleen, they transfer exosomes expressing the reporter marker GFP to spleen-resident DCs. Our results suggest that exchange of exosomes between DCs in lymphoid organs might constitute a potential mechanism by which passenger leukocytes transfer alloantigens to recipient’s APCs and amplify generation of donor-reactive T cells following transplantation.
Spontaneous Renal Allograft Acceptance Associated with “Regulatory” Dendritic Cells and IDO
Authors: Cook Charles H. , Bickerstaff Alice A. , Wang Jiao-Jing , Nadasdy Tibor , Della Pelle Patricia , Colvin Robert B. , Orosz Charles G.
Published: April 2014

MHC-mismatched DBA/2 renal allografts are spontaneously accepted by C57BL/6 mice by poorly understood mechanisms, but both immune regulation and graft acceptance develop without exogenous immune modulation. Previous studies have shown that this model of spontaneous renal allograft acceptance is associated with TGF-β-dependent immune regulation, suggesting a role for T regulatory cells. The current study shows that TGF-β immune regulation develops 30 days posttransplant, but is lost by 150 days posttransplant. Despite loss of detectable TGF-β immune regulation, renal allografts continue to function normally for >200 days posttransplantation. Because of its recently described immunoregulatory capabilities, we studied IDO expression in this model, and found that intragraft IDO gene expression progressively increases over time, and that IDO in “regulatory” dendritic cells (RDC) may contribute to regulation associated with long-term maintenance of renal allografts. Immunohistochemistry evaluation confirms the presence of both Foxp3+ T cells and IDO+ DCs in accepted renal allografts, and localization of both cell types within accepted allografts suggests the possibility of synergistic involvement in allograft acceptance. Interestingly, at the time when RDCs become detectable in spleens of allograft acceptors, ∼30% of these mice challenged with donor-matched skin allografts accept these skin grafts, demonstrating progression to “true” tolerance. Together, these data suggest that spontaneous renal allograft acceptance evolves through a series of transient mechanisms, beginning with TGF-β and T regulatory cells, which together may stimulate development of more robust regulation associated with RDC and IDO.
Absence of CTL Responses to Early Viral Antigens Facilitates Viral Persistence
Authors: Schildknecht Anita , Welti Sarah , Geuking Markus B. , Hangartner Lars , van den Broek Maries
Published: April 2014

CD8+ T cells are crucial for the control of intracellular pathogens such as viruses and some bacteria. Using lymphocytic choriomeningitis virus (LCMV) infection of mice—the prototypic arenavirus evolutionarily closely related to human Lassa fever and South American hemorrhagic fever viruses, we have shown previously that the kinetics of Ag presentation determine immunodominance of the LCMV-specific CTL response due to progressive exhaustion of LCMV nucleoprotein (NP)-specific CTL upon increasing viral load. In this study, we provide evidence that CTL against early LCMV NP-derived epitopes are more important in virus control than those against late glycoprotein-derived epitopes. We show that mice that are tolerant to all NP-derived T cell epitopes are severely compromised in their ability to control larger inocula of LCMV, supporting our hypothesis that CD8+ T cells specific for early viral Ags play a major role in acute virus control. Thus, the kinetics with which virus-derived T cell epitopes are presented has a strong impact on the efficacy of the antiviral immunity. This aspect should be taken into consideration for the development of vaccines.
Vesicle-Associated Membrane Protein-8/Endobrevin Negatively Regulates Phagocytosis of Bacteria in Dendritic Cells
Authors: Ho Yong Hou Sunny , Cai Deyu Tarika , Wang Cheng-Chun , Huang Dachuan , Wong Siew Heng
Published: April 2014

Phagocytosis is a specialized mechanism used by mammalian cells, particularly the cells of the immune system, such as dendritic cells (DC) and macrophages, to protect the host against infection. The process involves a complex cascade of pathways, from the ligation of surface receptors of phagocytes with components of the microorganism’s surface, formation of phagosomes and subsequently phagolysosomes, to the eventual presentation of foreign Ags. Vesicle-associated membrane protein (VAMP)-8/endobrevin has been shown previously to function in the endocytic pathways. Our results showed that VAMP-8 colocalized with lysosome-associated membrane protein-2, and a significant amount of VAMP-8 was recruited to the phagosomes during bacterial ingestion. However, overexpression of VAMP-8 significantly inhibited phagocytosis in DC. We also found that the phagocytic activity of VAMP-8−/− DC was significantly higher than wild-type VAMP-8+/+ DC, thus further confirming that VAMP-8 negatively regulates phagocytosis in immature DC.
Knockdown of Mgat5 Inhibits Breast Cancer Cell Growth with Activation of CD4+ T Cells and Macrophages
Authors: Li Dongqing , Li Yanmei , Wu Xianglei , Li Qiao , Yu Jing , Gen Jie , Zhang Xiao-Lian
Published: April 2014

N-acetylglucosaminyltransferase V (Mgat5 or GnT-V) is an enzyme that catalyzes β1–6 branching of N-acetylglucosamine on asparagine (N)-linked oligosaccharides (N-glycan) of cell proteins. The levels of Mgat5 glycan products commonly are increased in malignancies. Although Mgat5 is known to be important in tumor metastases, the effects of Mgat5 on host immune responses are not fully defined. In this study, a Mgat5 specific-short hairpin RNA (shRNA) vector was transfected into murine mammary adenocarcinoma MA782 cells to assess the effects of Mgat5 on tumor cell growth, T cells, and macrophages following inoculation of mice with shRNA-transfected cancer cells. The results showed that blocking expression of Mgat5-modified glycans in MA782 cells significantly suppressed tumor progression both in vivo and in vitro, strongly stimulated Th1 cytokine production, and enhanced opsonophagocytic capability of macrophages in vivo. Importantly, reduction of complex N-glycans on MA782 tumor cells by Mgat5-shRNA resulted in significantly increased proliferation and CD45 surface expression of CD4+ T cells. Our data suggest Mgat5-shRNA could serve as a useful tool to treat breast cancer as well as a powerful tool for the functional investigation of N-glycans and glycoprotein synthesis. Our data suggest that knockdown of Mgat5 inhibits breast cancer cells’ growth with activation of CD4+ T cells and macrophages.
Abnormal NF-κB Function Characterizes Human Type 1 Diabetes Dendritic Cells and Monocytes
Authors: Mollah Zia U. A. , Pai Saparna , Moore Craig , O’Sullivan Brendan J. , Harrison Matthew J. , Peng Judy , Phillips Karen , Prins Johannes B. , Cardinal John , Thomas Ranjeny
Published: April 2014

Dendritic cell (DC) differentiation is abnormal in type 1 diabetes mellitus (T1DM). However, the nature of the relationship between this abnormality and disease pathogenesis is unknown. We studied the LPS response in monocytes and monocyte-derived DCs isolated from T1DM patients and from non-T1DM controls. In T1DM patients, late LPS-mediated nuclear DNA binding by RelA, p50, c-Rel, and RelB was impaired as compared with type 2 DM, rheumatoid arthritis, and healthy subjects, associated with impaired DC CD40 and MHC class I induction but normal cytokine production. In TIDM monocytes, RelA and RelB were constitutively activated, and the src homology 2 domain-containing protein tyrosine phosphatase (SHP-1), a negative regulator of NF-κB, was overexpressed. Addition of sodium stibogluconate, a SHP-1 inhibitor, to DCs differentiating from monocyte precursors restored their capacity to respond to LPS in ∼60% of patients. The monocyte and DC NF-κB response to LPS is thus a novel phenotypic and likely pathogenetic marker for human T1DM. SHP-1 is at least one NF-κB regulatory mechanism which might be induced as a result of abnormal inflammatory signaling responses in T1DM monocytes.
Phylogenetic Conservation of Glycoprotein 96 Ability to Interact with CD91 and Facilitate Antigen Cross-Presentation
Authors: Robert Jacques , Ramanayake Thaminda , Maniero Gregory D. , Morales Heidi , Chida Asiya S.
Published: April 2014

Although the ability of gp96 to activate APCs and generate CD8 CTLs against peptides they chaperone through interaction with the endocytic receptors CD91 is supported by solid evidence, its biological relevance in immune surveillance is debated. We have used an evolutionary approach to determine whether gp96 interacts with receptors expressed on APCs and promotes MHC class I cross-presentation of minor histocompatibility Ags (H-Ags) to CTLs in the frog Xenopus. We show that in Xenopus gp96 binds the CD91 homolog at the surface of peritoneal leukocytes, and that this binding is inhibited by molar excess of unlabeled gp96 or the CD91 ligand α2-macroglobulin, by anti-CD91 Ab and by the specific CD91 antagonist receptor-associated protein. Surface binding followed by internalization of gp96 was confirmed by fluorescent microscopy. Furthermore, adoptive transfer of peritoneal leukocytes pulsed with as little as 800 ng of gp96 chaperoning minor H-Ags, but not minor H-Ag-free gp96, induces potent CD8 T cell infiltration and Ag-specific accelerated rejection of minor H-locus disparate skin grafts. Inhibition of gp96-CD91 interaction by pretreatment with anti-CD91 Ab and receptor-associated protein impairs both CD8 T cell infiltration and acute skin graft rejection. These data provide evidence of the conserved ability of gp96 to facilitate cross-presentation of chaperoned Ags by interacting with CD91. The persistence of this biological process for >350 million years that separate mammals and amphibians from a common ancestor strongly supports the proposition that gp96 and CD91 are critically involved in immune surveillance.
Expansion of Effector Memory TCR Vβ4+CD8+ T Cells Is Associated with Latent Infection-Mediated Resistance to Transplantation Tolerance
Authors: Stapler Dale , Lee Eun D. , Selvaraj Saranya A. , Evans Andrew G. , Kean Leslie S. , Speck Samuel H. , Larsen Christian P. , Gangappa Shivaprakash
Published: April 2014

Therapies that control largely T cell-dependent allograft rejection in humans also possess the undesirable effect of impairing T cell function, leaving transplant recipients susceptible to opportunistic viruses. Prime among these opportunists are the ubiquitous herpesviruses. To date, studies are lacking that address the effect of viruses that establish a true latent state on allograft tolerance or the effect of tolerance protocols on the immune control of latent viruses. By using a mixed chimerism-based tolerance-induction protocol, we found that mice undergoing latent infection with γHV68, a murine γ-herpesvirus closely related to human γ-herpesviruses such as EBV and Kaposi’s sarcoma-associated herpesvirus, significantly resist tolerance to allografts. Limiting the degree of virus reactivation or innate immune response did not reconstitute chimerism in latently infected mice. However, γHV68-infected mice showed increased frequency of CD8+ T cell alloreactivity and, interestingly, expansion of virus-induced, alloreactive, “effector/effector memory” TCR Vβ4+CD8+ T cells driven by the γHV68-M1 gene was associated with resistance to tolerance induction in studies using γHV68-M1 mutant virus. These results define the viral gene and immune cell types involved in latent infection-mediated resistance to allograft tolerance and underscore the influence of latent herpesviruses on allograft survival.
Selection of an Antibody Library Identifies a Pathway to Induce Immunity by Targeting CD36 on Steady-State CD8α+ Dendritic Cells
Authors: Tagliani Elisa , Guermonprez Pierre , Sepúlveda Jorge , López-Bravo María , Ardavín Carlos , Amigorena Sebastian , Benvenuti Federica , Burrone Oscar R.
Published: April 2014

Improvement of the strategy to target tumor Ags to dendritic cells (DCs) for immunotherapy requires the identification of the most appropriate ligand/receptor pairing. We screened a library of Ab fragments on mouse DCs to isolate new potential Abs capable of inducing protective immune responses. The screening identified a high-affinity Ab against CD36, a multi-ligand scavenger receptor primarily expressed by the CD8α+ subset of conventional DCs. The Ab variable regions were genetically linked to the model Ag OVA and tested in Ag presentation assays in vitro and in vivo. Anti-CD36-OVA was capable of delivering exogenous Ags to the MHC class I and MHC class II processing pathways. In vivo, immunization with anti-CD36-OVA induced robust activation of naive CD4+ and CD8+ Ag-specific T lymphocytes and the differentiation of primed CD8+ T cells into long-term effector CTLs. Vaccination with anti-CD36-OVA elicited humoral and cell-mediated protection from the growth of an Ag-specific tumor. Notably, the relative efficacy of targeting CD11c/CD8α+ via CD36 or DEC205 was qualitatively different. Anti-DEC205-OVA was more efficient than anti-CD36-OVA in inducing early events of naive CD8+ T cell activation. In contrast, long-term persistence of effector CTLs was stronger following immunization with anti-CD36-OVA and did not require the addition of exogenous maturation stimuli. The results identify CD36 as a novel potential target for immunotherapy and indicate that the outcome of the immune responses vary by targeting different receptors on CD8α+ DCs.
Differential Activation of Dual Promoters Alters Dβ2 Germline Transcription during Thymocyte Development
Authors: McMillan Ruth E. , Sikes Michael L.
Published: April 2014

Ag receptor genes are assembled through somatic rearrangements of V, D, and J gene segments. This process is directed in part by transcriptional enhancers and promoters positioned within each gene locus. Whereas enhancers coordinate reorganization of large chromatin stretches, promoters are predicted to facilitate the accessibility of proximal downstream gene segments. In TCR β locus, rearrangement initiates at two D-J cassettes, each of which exhibits transcriptional activity coincident with DJ rearrangement in CD4/CD8 double-negative pro-T cells. Consistent with a model of promoter-facilitated recombination, assembly of the DJβ1 cassette is dependent on a Dβ1 promoter (PDβ1) positioned immediately 5′ of the D. Assembly of DJβ2 proceeds independent from that of DJβ1, albeit with less efficiency. To gain insight into the mechanisms that selectively alter D usage, we have defined transcriptional regulation at Dβ2. We find that both DJβ cassettes generate germline messages in murine CD44+CD25− double-negative 1 cells. However, transcription of unrearranged DJβ2 initiates at multiple sites 400–550 bp downstream of the Dβ2. Unexpectedly, loci from which germline promoter activity has been deleted by DJ rearrangement redirect transcription to sites immediately 5′ of the new DJβ2 joint. Our analyses suggest that 3′-PDβ2 activity is largely controlled by NF-κB RelA, whereas 5′-PDβ2 activity directs germline transcription of DJβ2 joints from initiator elements 76 bp upstream of the Dβ2 5′ recombination signal sequence. The unique organization and timing of Dβ2 promoter activity are consistent with a model in which promoter placement selectively regulates the rearrangement potential of Dβ2 during TCR β locus assembly.
Through Regulation of TCR Expression Levels, anIdd7Region Gene(s) Interactively Contributes to the Impaired Thymic Deletion of Autoreactive Diabetogenic CD8+ T Cells in Nonobese Diabetic Mice
Authors: Serreze David V. , Choisy-Rossi Caroline Morgane , Grier Alexandra E. , Holl T. Mathew , Chapman Harold D. , Gahagan J. Reed , Osborne Melissa A. , Zhang Weidong , King Benjamin L. , Brown Aaron , Roopenian Derry , Marron Michele P.
Published: April 2014

When expressed in NOD, but not C57BL/6 (B6) genetic background mice, the common class I variants encoded by the H2g7 MHC haplotype aberrantly lose the ability to mediate the thymic deletion of autoreactive CD8+ T cells contributing to type 1 diabetes (T1D). This indicated some subset of the T1D susceptibility (Idd) genes located outside the MHC of NOD mice interactively impair the negative selection of diabetogenic CD8+ T cells. In this study, using both linkage and congenic strain analyses, we demonstrate contributions from a polymorphic gene(s) in the previously described Idd7 locus on the proximal portion of Chromosome 7 predominantly, but not exclusively, determines the extent to which H2g7 class I molecules can mediate the thymic deletion of diabetogenic CD8+ T cells as illustrated using the AI4 TCR transgenic system. The polymorphic Idd7 region gene(s) appears to control events that respectively result in high vs low expression of the AI4 clonotypic TCR α-chain on developing thymocytes in B6.H2g7 and NOD background mice. This expression difference likely lowers levels of the clonotypic AI4 TCR in NOD, but not B6.H2g7 thymocytes, below the threshold presumably necessary to induce a signaling response sufficient to trigger negative selection upon Ag engagement. These findings provide further insight to how susceptibility genes, both within and outside the MHC, may interact to elicit autoreactive T cell responses mediating T1D development in both NOD mice and human patients.
Glycosylation-Dependent Interactions of C-Type Lectin DC-SIGN with Colorectal Tumor-Associated Lewis Glycans Impair the Function and Differentiation of Monocyte-Derived Dendritic Cells
Authors: Nonaka Motohiro , Ma Bruce Yong , Murai Ryuuya , Nakamura Natsuko , Baba Makoto , Kawasaki Nobuko , Hodohara Keiko , Asano Shinji , Kawasaki Toshisuke
Published: April 2014

Dendritic cells (DCs) are APCs that play an essential role by bridging innate and adaptive immunity. DC-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) is one of the major C-type lectins expressed on DCs and exhibits high affinity for nonsialylated Lewis (Le) glycans. Recently, we reported the characterization of oligosaccharide ligands expressed on SW1116, a typical human colorectal carcinoma recognized by mannan-binding protein, which is a serum C-type lectin and has similar carbohydrate-recognition specificities as DC-SIGN. These tumor-specific oligosaccharide ligands were shown to comprise clusters of tandem repeats of Lea/Leb epitopes. In this study, we show that DC-SIGN is involved in the interaction of DCs with SW1116 cells through the recognition of aberrantly glycosylated forms of Lea/Leb glycans on carcinoembryonic Ag (CEA) and CEA-related cell adhesion molecule 1 (CEACAM1). DC-SIGN ligands containing Lea/Leb glycans are also highly expressed on primary cancer colon epithelia but not on normal colon epithelia, and DC-SIGN is suggested to be involved in the association between DCs and colorectal cancer cells in situ by DC-SIGN recognizing these cancer-related Le glycan ligands. Furthermore, when monocyte-derived DCs (MoDCs) were cocultured with SW1116 cells, LPS-induced immunosuppressive cytokines such as IL-6 and IL-10 were increased. The effects were significantly suppressed by blocking Abs against DC-SIGN. Strikingly, LPS-induced MoDC maturation was inhibited by supernatants of cocultures with SW1116 cells. Our findings imply that colorectal carcinomas affecting DC function and differentiation through interactions between DC-SIGN and colorectal tumor-associated Le glycans may induce generalized failure of a host to mount an effective antitumor response.
Human Lymphatic Endothelial Cells Express Multiple Functional TLRs
Authors: Pegu Amarendra , Qin Shulin , Fallert Junecko Beth A. , Nisato Riccardo E. , Pepper Michael S. , Reinhart Todd A.
Published: April 2014

The lymphatic endothelium is the preferred route for the drainage of interstitial fluid from tissues and also serves as a conduit for peripheral dendritic cells (DCs) to reach draining lymph nodes. Lymphatic endothelial cells (LECs) are known to produce chemokines that recruit Ag-loaded DCs to lymphatic vessels and therefore are likely to regulate the migration of DCs to lymph nodes. TLRs are immune receptors that recognize pathogen associated molecular patterns and then signal and stimulate production of inflammatory chemokines and cytokines that contribute to innate and adaptive immune responses. TLRs are known to be expressed by a wide variety of cell types including leukocytes, epithelial cells, and endothelial cells. Because the TLR expression profile of LECs remains largely unexamined, we have undertaken a comprehensive study of the expression of TLR1–10 mRNAs and protein in primary human dermal (HD) and lung LECs as well as in htert-HDLECs, which display a longer life-span than HDLECs. We found that all three cell types expressed TLR1–6 and TLR9. The responsiveness of these LECs to a panel of ligands for TLR1–9 was measured by real-time RT-PCR, ELISA, and flow cytometry, and revealed that the LECs responded to most but not all TLR ligands by increasing expression of inflammatory chemokines, cytokines, and adhesion molecules. These findings provide insight into the ability of cells of the lymphatic vasculature to respond to pathogens and potential vaccine adjuvants and shape peripheral environments in which DCs will acquire Ag and environmental cues.
Stimulation of Enhanced CD8 T Cell Responses Following Immunization with a Hyper-Antigen Secreting Intracytosolic Bacterial Pathogen
Authors: Smithey Megan J. , Brandt Suzanne , Freitag Nancy E. , Higgins Darren E. , Bouwer H. G. Archie
Published: April 2014

The intracytosolic niche for replication of Listeria monocytogenes (Lm) facilitates delivery of bacteria-derived Ags into the MHC class I pathway for subsequent stimulation of CD8 effector T cells. Using Lm strains that are equivalent for in vivo virulence yet express marked differences in the level of secretion of a protective target Ag, we have evaluated how these specific differences in secretion levels influences the magnitude and effector function of Ag-specific CD8 T cell responses following Lm injection. Immunization with low doses of a hyperantigen-secreting Lm strain stimulated enhanced target-Ag specific CD8 T cell responses compared with the magnitude stimulated following immunization with the same dose of wild-type Lm. The enhanced determinant-specific response was also evident by in vivo CTL activity, increased numbers of memory cells 4 wk following immunization, and enhanced antilisterial protection following a challenge infection. Initiation of antibiotic treatment 24 h following infection with wild-type Lm markedly reduced the magnitude of the effector CD8 T cell response. In contrast, antibiotic treatment initiated 24 h following immunization with the hyperantigen secreting strain of Lm did not impact the frequency of the target-Ag specific CD8 T cells. Thus, immunization with a low dose of a hyperantigen secreting Lm strain, followed by antibiotic treatment to limit the extent of the infection, may represent a safe strategy for the stimulation of enhanced effector CD8 T cell responses to specific Ag by a rLm vaccine.
Mycobacterial Lipopeptides Elicit CD4+ CTLs in Mycobacterium tuberculosis-Infected Humans
Authors: Bastian Max , Braun Tobias , Bruns Heiko , Röllinghoff Martin , Stenger Steffen
Published: April 2014

In searching for immunogenic molecules with the potential to induce protective immune responses against tuberculosis, we developed an ex vivo model to study frequency, phenotype, and effector functions of human T lymphocytes recognizing hydrophobic Ags of Mycobacterium tuberculosis (M.Tb). To obtain unbiased results, we characterized T lymphocytes responding to a crude cell wall extract (chloroform methanol extract of M.Tb (M.Tb-CME)) containing a broad spectrum of mycobacterial glycolipids and lipopeptides. A significant proportion of T lymphocytes recognized M.Tb-CME (290 IFN-γ+ T cells/105 PBMCs) and developed to effector memory cells as determined by the expression of CD45RO and the chemokine receptors CXCR3 and CCR5. Expanded lymphocytes fulfilled all criteria required for an efficient immune response against tuberculosis: 1) release of macrophage-activating Th1 cytokines and chemokines required for the spatial organization of local immune responses, 2) cytolytic activity against Ag-pulsed macrophages, and 3) recognition of infected macrophages and killing of the intracellular bacteria. Phenotypically, M.Tb-CME-expanded cells were CD4+ and MHC class II restricted, challenging current concepts that cytotoxic and antimicrobial effector cells are restricted to the CD8+ T cell subset. Pretreatment of M.Tb-CME with protease or chemical delipidation abrogated the biological activity, suggesting that responses were directed toward mycobacterial lipopeptides. These findings suggest that lipidated peptides are presented by M.Tb-infected macrophages and elicit CD4+ cytolytic and antimicrobial T lymphocytes. Our data support an emerging concept to include hydrophobic microbial Ags in vaccines against tuberculosis.
Lymphotoxin-α1β2 and LIGHT Induce Classical and Noncanonical NF-κB-Dependent Proinflammatory Gene Expression in Vascular Endothelial Cells
Authors: Madge Lisa A. , Kluger Martin S. , Orange Jordan S. , May Michael J.
Published: April 2014

Activation of the classical and noncanonical NF-κB pathways by ligation of the lymphotoxin (LT)-β receptor (LTβR) plays a crucial role in lymphoid organogenesis and in the generation of ectopic lymphoid tissue at sites of chronic inflammation. Within these microenvironments, LTβR signaling regulates the phenotype of the specialized high endothelial cells. However, the direct effects of LTβR ligation on endothelial cells remain unclear. We therefore questioned whether LTβR ligation could directly activate endothelial cells and regulate classical and noncanonical NF-κB-dependent gene expression. We demonstrate that the LTβR ligands LIGHT and LTα1β2 activate both NF-κB pathways in HUVECs and human dermal microvascular endothelial cells (HDMEC). Classical pathway activation was less robust than TNF-induced signaling; however, only LIGHT and LTα1β2 and not TNF activated the noncanonical pathway. LIGHT and LTα1β2 induced the expression of classical NF-κB-dependent genes in HUVEC, including those encoding the adhesion molecules E-selectin, ICAM-1, and VCAM-1. Consistent with this stimulation, LTβR ligation up-regulated T cell adhesion to HUVEC. Furthermore, the homeostatic chemokine CXCL12 was up-regulated by LIGHT and LTα1β2 but not TNF in both HUVEC and HDMEC. Using HUVEC retrovirally transduced with dominant negative IκB kinase α, we demonstrate that CXCL12 expression is regulated by the noncanonical pathway in endothelial cells. Our findings therefore demonstrate that LTβR ligation regulates gene expression in endothelial cells via both NF-κB pathways and we identify CXCL12 as a bona fide noncanonical NF-κB-regulated gene in these cells.
Transcriptional Complex Formation of c-Fos, STAT3, and Hepatocyte NF-1α Is Essential for Cytokine-Driven C-Reactive Protein Gene Expression
Authors: Nishikawa Teppei , Hagihara Keisuke , Serada Satoshi , Isobe Tomoyasu , Matsumura Atsumi , Song Jian , Tanaka Toshio , Kawase Ichiro , Naka Tetsuji , Yoshizaki Kazuyuki
Published: April 2014

C-reactive protein (CRP) is a sensitive marker and mediator of inflammation, whereas IL-6 blocking therapy can normalize serum levels of CRP in chronic inflammatory diseases. We investigated the precise synergistic induction mechanism of CRP gene expression by IL-1 and IL-6 in Hep3B cells. In the early induction phase, IL-1 inhibited IL-6-mediated CRP gene expression, and NF-κB p65 inhibited the luciferase activity of pGL3-CRP by IL-1 plus IL-6 even in the presence of overexpressed STAT3. In the late induction phase, we focused on JNK and p38 activated by IL-1. SP600125 reduced the expression of the CRP gene induced by IL-1 plus IL-6. Unexpectedly, overexpression of c-Fos dramatically enhanced the luciferase activity by IL-1 and IL-6 even though the CRP gene has no AP-1 response element (RE) in its promoter. The augmentative effect of c-Fos required the presence of STAT3 and 3′-hepatocyte NF-1 (HNF-1) RE, which were eliminated by dominant negative STAT3 and HNF-1α, respectively. SB203580 inhibited the phosphorylation of c-Fos enhanced by IL-1 plus IL-6, and diminished expression of the CRP gene. Immunoprecipitation, Western blot analysis, the Supershift assay using a CRP oligonucleotide containing STAT3 and 3′-HNF-1 RE, and the chromatin immunoprecipitation assay demonstrated that c-Fos/STAT3/HNF-1α forms a complex on the CRP gene promoter. Because human fetus liver cells failed to express c-Fos/STAT3/HNF-1α showed no CRP production, transcriptional complex formation of c-Fos/STAT3/HNF-1α is essential for the synergistic induction of CRP gene expression by IL-1 plus IL-6. Our findings fully explain the clinical results of IL-6 blocking therapy and are expected to contribute to the development of a therapeutic strategy for chronic inflammatory diseases.