bluuebunny/crossref_metadata_2025 huggingface dataset:
Negative Control of Store-Operated Ca2+ Influx by B Cell Receptor Cross-Linking
Authors: Hashimoto Akiko , Hirose Kenzo , Kurosaki Tomohiro , Iino Masamitsu
Published: April 2014

An increase in the intracellular Ca2+ concentration by B cell receptor (BCR) cross-linking plays important roles in the regulation of B cell functions. [Ca2+]i is regulated by Ca2+ release from the Ca2+ store as well as store-operated Ca2+ influx (SOC). Protein tyrosine kinases downstream of BCR cross-linking were shown to regulate the mechanism for Ca2+ release. However, it remains elusive whether BCR cross-linking regulates SOC or not. In this study, we examined the effect of BCR cross-linking on thapsigargin-induced SOC in the DT40 B cells. We found that the SOC-mediated increase in intracellular Ca2+ concentration was inhibited by BCR cross-linking. Using a membrane-potential-sensitive dye, we found that BCR cross-linking induced depolarization, which is expected to decrease the driving force of Ca2+ influx and SOC channel conductance. When membrane potential was held constant by the transmembrane K+ concentration gradient in the presence of valinomycin, the BCR-mediated inhibition of SOC was still observed. Thus, the BCR-mediated inhibition of SOC involves both depolarization-dependent and depolarization-independent mechanisms of SOC inhibition. The depolarization-independent inhibition of the SOC was abolished in Lyn-deficient, but not in Bruton’s tyrosine kinase-, Syk- or SHIP (Src homology 2 domain containing phosphatidylinositol 5′-phosphatase)-deficient cells, indicating that Lyn is involved in the inhibition. These results show novel pathways of BCR-mediated SOC regulations.
Lymphotoxin α−/− Mice Develop Functionally Impaired CD8+ T Cell Responses and Fail to Contain Virus Infection of the Central Nervous System
Authors: Kumaraguru Udayasankar , Davis Ila A. , Deshpande Shilpa , Tevethia Satvir S. , Rouse Barry T.
Published: April 2014

Recent observations have indicated that viral persistence and tumor spreading could occur because of effector function-defective CD8+ T cells. Although chronic exposure to Ag, lack of CD4 help, and epitope dominance are suggested to interfere with CTL differentiation, mechanisms underlying the defective effector function remain obscure. We demonstrate in this report that lymphotoxin α-deficient mice develop CD8+ T cells at normal frequencies when infected with HSV or immunized with OVA Ag but show impaired cytotoxic and cytokine-mediated effector functions resulting in enhanced susceptibility to HSV-induced encephalitis. Although these cells display near normal levels of perforin and Fas ligand, they remain largely at a naive state as judged by high expression of CD62 ligand and failure to up-regulate activation or memory markers. In particular, these CD8+ T cells revealed inadequate expression of the IL-12 receptor, thus establishing a link between CTL differentiation and LTα possibly through regulation of IL-12 receptor. Viruses and tumors could evade immunity by targeting the same pathway.
Transcriptional Down-Regulation of CXC Chemokine Receptor 4 Induced by Impaired Association of Transcription Regulator YY1 with c-Myc in Human Herpesvirus 6-Infected Cells
Authors: Hasegawa Atsuhiko , Yasukawa Masaki , Sakai Ikuya , Fujita Shigeru
Published: April 2014

We have recently reported that down-regulation of CXC chemokine receptor (CXCR) 4 in CD4+ T lymphocytes is induced by human herpesvirus (HHV) 6 infection. In this study, we further studied the mechanisms of HHV-6-induced CXCR4 down-regulation, focusing on the regulation of CXCR4 transcription. Down-regulation of CXCR4 transcription was detected in HHV-6A-infected JJHAN and HHV-6B-infected MT-4 cell lines, as we had previously reported for HHV-6-infected peripheral blood CD4+ T lymphocytes. Luciferase assays revealed that a YY1-binding site around −320 relative to the transcription start site is important for down-regulation of CXCR4 transcription in HHV-6-infected cells. The binding activity of YY1, which is a repressor of CXCR4 transcription, to the CXCR4 promoter appeared to significantly increase in HHV-6-infected cells compared with the binding activity in mock-infected cells. Immunoprecipitation assays showed that in HHV-6-infected cells association of c-Myc with YY1 was decreased and that of Max with c-Myc was increased, whereas association of Mad with Max appeared to be decreased. The amounts of each of YY1, c-Myc, Max, and Mad proteins synthesized in cells were not altered by HHV-6 infection. These data indicate that the decreased association of YY1 with c-Myc that is caused by impaired interaction in the c-Myc/Max/Mad network results in increased binding activity of YY1 to the CXCR4 promoter, mediating down-regulation of CXCR4 production in HHV-6-infected cells.
Rac2 Is an Essential Regulator of Neutrophil Nicotinamide Adenine Dinucleotide Phosphate Oxidase Activation in Response to Specific Signaling Pathways
Authors: Kim Chaekyun , Dinauer Mary C.
Published: April 2014

Rac2 is a hematopoietic-specific Rho family GTPase implicated as an important constituent of the NADPH oxidase complex and shares 92% amino acid identity with the ubiquitously expressed Rac1. In bone marrow (BM) neutrophils isolated from rac2−/− mice generated by gene targeting, we previously reported that PMA-induced superoxide production was reduced by about 4-fold, which was partially corrected in TNF-α-primed BM neutrophils and in peritoneal exudate neutrophils. We investigated receptor-mediated activation of the NADPH oxidase in the current study, finding that superoxide production in rac2−/− BM and peritoneal exudate neutrophils was normal in response to opsonized zymosan, reduced to 22% of wild type in response to IgG-coated SRBC, and almost absent in response to fMLP. In wild-type murine BM neutrophils, phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), p38 mitogen-activated protein kinase, c-Jun N-terminal kinase, and Akt was induced by PMA or fMLP, which was decreased in rac2−/− neutrophils for ERK1/2 and p38. Activation of p38 by either opsonized zymosan or IgG-coated SRBC was similar in wild-type and rac2−/− cells. Inhibition of ERK1/2 or p38 activation using either PD98059 or SB203580, respectively, had only a modest effect on fMLP-elicited superoxide production and no effect on the PMA-induced response. These data provide genetic evidence supporting an important role for Rac2 in regulating neutrophil NADPH oxidase activation downstream of chemoattractant and Fcγ receptors. The effect of Rac2 deficiency on superoxide production is probably exerted through multiple pathways, including those independent of mitogen-activated protein kinase activation.
Hepatocyte Growth Factor Is a Regulator of Monocyte-Macrophage Function
Authors: Galimi Francesco , Cottone Erika , Vigna Elisa , Arena Nicolò , Boccaccio Carla , Giordano Silvia , Naldini Luigi , Comoglio Paolo M.
Published: April 2014

Hepatocyte growth factor (HGF) is a potent paracrine mediator of stromal/epithelial interactions, which is secreted as a matrix-associated inactive precursor (pro-HGF) and locally activated by tightly controlled urokinase cleavage. It induces proliferation and motility in epithelial and endothelial cells, and plays a role in physiological and pathological processes involving invasive cell growth, such as angiogenesis and parenchymal regeneration. We now report that HGF induces directional migration and cytokine secretion in human monocytes. Monocyte activation by endotoxin and IL-1β results in the up-regulation of the HGF receptor expression and in the induction of cell-associated pro-HGF convertase activity, thus enhancing cell responsiveness to the factor. Furthermore, we provide evidence for the secretion of biologically active HGF by activated monocytes, implying an autocrine stimulation. Altogether, these data indicate that monocyte function is modulated by HGF in a paracrine/autocrine manner, and provide a new link between stromal environment and mononuclear phagocytes.
Neutral Endopeptidase Terminates Substance P-Induced Inflammation in Allergic Contact Dermatitis
Authors: Scholzen Thomas E. , Steinhoff Martin , Bonaccorsi Paola , Klein Robin , Amadesi Silvia , Geppetti Piero , Lu Bao , Gerard Norma P. , Olerud John E. , Luger Thomas A. , Bunnett Nigel W. , Grady Eileen F. , Armstrong Cheryl A. , Ansel John C.
Published: April 2014

Sensory nerve-derived neuropeptides such as substance P demonstrate a number of proinflammatory bioactivities, but less is known about their role in inflammatory skin disease. The cell surface metalloprotease neutral endopeptidase (NEP) is the principal proteolytic substance P-degrading enzyme. This study tests the hypothesis that the absence of NEP results in dysregulated inflammatory skin responses. The effector phase of allergic contact dermatitis (ACD) responses was examined in NEP−/− knockout and NEP+/+ wild-type mice and compared with the irritant contact dermatitis response in these animals. NEP was found to be normally immunolocalized in epidermal keratinocytes and dermal blood vessels. The ACD ear swelling response was 2.5-fold higher in animals lacking NEP and was accompanied by a significant increase in plasma extravasation and infiltration of inflammatory leukocytes. The augmented ACD response in NEP−/− animals was abrogated by either administration of a neurokinin receptor 1 antagonist or by repeated pretreatment with topical capsaicin. Similar to NEP−/− mice, the acute inhibition of NEP in NEP+/+ animals resulted in an augmented ACD response. In contrast to the ACD responses, little differences were observed in the irritant contact dermatitis response of NEP−/− compared with NEP+/+ animals after epicutaneous application of the skin irritants croton oil or SDS. Thus, these results indicate that NEP and cutaneous neuropeptides have a significant role in the pathogenesis of ACD.
Type 1 Diabetes-Predisposing MHC Alleles Influence the Selection of Glutamic Acid Decarboxylase (GAD) 65-Specific T Cells in a Transgenic Model
Authors: Abraham Roshini S. , Wen Li , Marietta Eric V. , David Chella S.
Published: April 2014

The genetic factors that contribute to the etiology of type 1 diabetes are still largely uncharacterized. However, the genes of the MHC (HLA in humans) have been consistently associated with susceptibility to disease. We have used several transgenic mice generated in our laboratory, bearing susceptible or resistant HLA alleles, in the absence of endogenous MHC class II (Aβo), to study immune responses to the autoantigen glutamic acid decarboxylase (GAD) 65 and its relevance in determining the association between autoreactivity and disease pathogenesis. Mice bearing diabetes-susceptible haplotypes, HLA DR3 (DRB1*0301) or DQ8 (DQB1*0302), singly or in combination showed spontaneous T cell reactivity to rat GAD 65, which is highly homologous to the self Ag, mouse GAD 65. The presence of diabetes-resistant or neutral alleles, such as HLA DQ6 (DQB1*0602) and DR2 (DRB1*1502) prevented the generation of any self-reactive responses to rat GAD. In addition, unmanipulated Aβo/DR3, Aβo/DQ8, and Aβo/DR3/DQ8 mice recognized specific peptides, mainly from the N-terminal region of the GAD 65 molecule. Most of these regions are conserved between human, mouse, and rat GAD 65. Further analysis revealed that the reactivity was mediated primarily by CD4+ T cells. Stimulation of these T cells by rat GAD 65 resulted in the generation of a mixed Th1/Th2 cytokine profile in the Aβo/DR3/DQ8, Aβo/DR3, and Aβo/DQ8 mice. Thus, the presence of diabetes-associated genes determines whether immune tolerance is maintained to islet autoantigens, but autoreactivity in itself is not sufficient to induce diabetes.
Both γδ T Cells and NK Cells Inhibit the Engraftment of Xenogeneic Rat Bone Marrow Cells and the Induction of Xenograft Tolerance in Mice
Authors: Nikolic Boris , Cooke David T. , Zhao Guiling , Sykes Megan
Published: April 2014

In murine allogeneic bone marrow transplantation recipients, treatment of the hosts with a nonmyeloablative regimen, including depleting anti-CD4 and anti-CD8 mAbs, allows establishment of long-term mixed chimerism and donor-specific tolerance. However, in the xenogeneic rat-to-mouse combination, additional anti-Thy1.2 and anti-NK1.1 mAbs are required. We have now attempted to identify the xenoresistant mouse cell populations that are targeted by anti-NK1.1 and anti-Thy1.2 mAbs. C57BL/6 (B6) wild-type, B6 TCRβ−/−, and B6 TCRδ−/− mice received anti-CD4 and anti-CD8 mAbs, followed by 3 Gy of whole body irradiation, 7 Gy of thymic irradiation, and transplantation of T cell-depleted rat bone marrow cells. Anti-NK1.1 and anti-Thy1.2 mAbs were additionally administered to some groups. Increased rat chimerism was observed in TCRδ−/− mice treated with anti-CD4, anti-CD8, and anti-NK1.1 mAbs compared with similarly treated TCRβ−/− mice. In TCRβ−/− mice, but not in TCR δ−/− mice, donor chimerism was increased by treatment with anti-Thy1.2 mAb, indicating that CD4−CD8−TCRγδ+Thy1.2+NK1.1− cells (γδ T cells) are involved in the rejection of rat marrow. In addition, chimerism was enhanced in both TCRβ−/− and TCRδ−/− mice treated with anti-CD4, anti-CD8, and anti-Thy1.2 mAbs by the addition of anti-NK1.1 mAb to the conditioning regimen. Donor-specific skin graft prolongation was enhanced by anti-Thy1.2 and anti-NK1.1 mAbs in TCRδ−/− mice. Therefore, in addition to CD4 and CD8 T cells, γδ T cells and NK cells play a role in resisting engraftment of rat marrow and the induction of xenograft tolerance in mice.
Targeting Murine Immune Responses to Selected T Cell- or Antibody-Defined Determinants of the Hepatitis B Surface Antigen by Plasmid DNA Vaccines Encoding Chimeric Antigen
Authors: Schirmbeck Reinhold , Zheng Xin , Roggendorf Michael , Geissler Michael , Chisari Francis V. , Reimann Jörg , Lu Mengji
Published: April 2014

By exchanging sequences from the middle-surface (MS) and small-surface (S) Ag of hepatitis B virus (HBV) with corresponding sequences of the MS Ag of woodchuck hepatitis virus, we constructed chimeric MS variants. Using these constructs as DNA vaccines in mice, we selectively primed highly specific (non-cross-reactive) Ab responses to pre-S2 of the HBV MS Ag and the “a” determinant of the HBV S Ag, as well as Ld- or Kb-restricted CTL responses to HBV S epitopes. In transgenic mice that constitutively express large amounts of HBV surface Ag in the liver we could successfully suppress serum antigenemia (but not Ag production in the liver) by adoptive transfer of anti-pre-S2 or anti-“a” immunity but not CTL immunity. DNA vaccines greatly facilitate construction of chimeric fusion Ags that efficiently prime specific, high-affinity Ab and CTL responses. Such vaccines, in which sequences of an Ag of interest are exchanged between different but related viruses, are interesting tools for focusing humoral or cellular immunity on selected antigenic determinants and elucidating their biological role.
Cutting Edge: Two Distinct Mechanisms Lead to Impaired T Cell Homeostasis in Janus Kinase 3- and CTLA-4-Deficient Mice
Authors: Gozalo-Sanmillan Sara , McNally James M. , Lin Meei Y. , Chambers Cynthia A. , Berg Leslie J.
Published: April 2014

Cytokine receptor signaling and costimulatory receptor signaling play distinct roles in T cell activation. Nonetheless, deficiencies in either of these pathways lead to seemingly similar phenotypes of impaired T cell homeostasis. A dramatic expansion of CD4+ peripheral T cells with an activated phenotype has been observed in both Janus kinase (Jak) 3-deficient and CTLA-4-deficient mice. Despite these similarities, the mechanisms driving T cell expansion may be distinct. To address this possibility, we examined the TCR repertoire of peripheral T cells in Jak3−/− and CTLA-4−/− mice using complementarity-determining region 3 spectratype analysis. Interestingly, a restricted and highly biased TCR repertoire was observed in the Jak3−/− T cells, strongly supporting a role for foreign Ag in the activation and expansion of these cells. In contrast, CTLA-4−/− T cells had a diverse and unbiased TCR repertoire, suggestive of a universal, Ag-independent mechanism of activation and expansion. These findings provide insight into the diverse mechanisms controlling T cell homeostasis.
Cutting Edge: Restoration of the Ability to Generate CTL in Mice Immune to Adenovirus by Delivery of Virus in a Collagen-Based Matrix
Authors: Siemens D. Robert , Elzey Bennett D. , Lubaroff David M. , Bohlken Caitlin , Jensen Robert J. , Swanson Axel Karl , Ratliff Timothy L.
Published: April 2014

Viruses are commonly used for the delivery of genes coding for tumor-associated Ags to elicit tumor-specific immune responses. The success of viral vectors has been limited in preclinical and clinical trials in part because of antiviral immunity. We investigated the ability of a collagen-based matrix (Gelfoam; Pharmacia and Upjohn, Kalamazoo, MI) to improve CTL activation by recombinant adenovirus. The data show that coinjection of Gelfoam with type 5 adenovirus recombinant for prostate-specific Ag (Ad5-PSA) enhanced CTL activation. Ad5-PSA priming in Gelfoam also abrogated the inhibitory effects of adenoviral immunity on CTL activation in mice naive to PSA but immune to adenovirus. Finally, Gelfoam enhanced immunization in a self-Ag model using type 5 adenovirus recombinant for membrane-bound OVA (Ad5-mOVA) in rat insulin promoter (RIP)-mOVA-transgenic mice. Thus, Gelfoam enhances CTL activation by recombinant viral vectors in a setting where preformed Ab to the virus is present and also in a tolerant self-Ag model.
Stem Cell Factor and FLT3-Ligand Are Strictly Required to Sustain the Long-Term Expansion of Primitive CD34+DR− Dendritic Cell Precursors
Authors: Curti Antonio , Fogli Miriam , Ratta Marina , Tura Sante , Lemoli Roberto M.
Published: April 2014

We studied cytokine-driven differentiation of primitive human CD34+HLA-DR− cells to myeloid dendritic cells (DC). Hemopoietic cells were grown in long-term cultures in the presence of various combinations of early acting cytokines such as FLT3-ligand (FLT3-L) and stem cell factor (SCF) and the differentiating growth factors GM-CSF and TNF-α. Two weeks of incubation with GM-CSF and TNF-α generated fully functional DC. However, clonogenic assays demonstrated that CFU-DC did not survive beyond 1 wk in liquid culture regardless of whether FLT3-L and/or SCF were added. FLT3-L or SCF alone did not support DC maturation. However, the combination of the two early acting cytokines allowed a 100-fold expansion of CFU-DC for >1 month. Phenotypic analysis demonstrated the differentiation of CD34+DR− cells into CD34−CD33+DR+CD14+ cells, which were intermediate progenitors capable of differentiating into functionally active DC upon further incubation with GM-CSF and TNF-α. As expected, GM-CSF and TNF-α generated DC from committed CD34+DR+ cells. However, only SCF, with or without FLT3-L, induced the expansion of DC precursors for >4 wk, as documented by secondary clonogenic assays. This demonstrates that although GM-CSF and TNF-α do not require additional cytokines to generate DC from primitive human CD34+DR− progenitor cells, they do force terminal differentiation of DC precursors. Conversely, FLT3-L and SCF do not directly affect DC differentiation, but instead sustain the long-term expansion of CFU-DC, which can be induced to produce mature DC by GM-CSF and TNF-α.
The Generation of Th Memory in Neonates Versus Adults: Prolonged Primary Th2 Effector Function and Impaired Development of Th1 Memory Effector Function in Murine Neonates
Authors: Adkins Becky , Bu Yurong , Guevara Patricia
Published: April 2014

Immunization during the neonatal period often results in Th2-biased secondary responses. To understand the regulation of this phenomenon, we have examined all phases of Th development, from the generation of primary effectors to the duration of the primary effector stage to the production of memory effector function. First, we had previously reported that although primary responses in the neonatal lymph nodes are mature, mixed Th1/Th2-like, primary responses in the spleens of the same animals are exclusively Th2-like. To determine whether Th2-dominant secondary responses are due to the Th2-polarized primary function in the spleen, neonates were splenectomized before immunization. Even in the absence of primary neonatal splenic responses, the secondary responses of neonates were Th2 dominant. Thus, the overwhelmingly Th2 primary responses in the neonatal spleen are not required to generate Th2-dominant memory in the lymph nodes. Second, we have compared the kinetics of the primary response phase in neonates and adults. In adults, Ag-specific Th2 function disappeared rapidly from both the lymph nodes and spleen. In contrast, primary Th2 function persisted out to 5 wk in both neonatal organs. Third, the generation of Th memory responses was examined in animals initially immunized as neonates and in adults. These experiments demonstrated that neonates are selectively impaired in the development of Th1 memory effector function. Together, these results indicate that neonates are biased to Th2 function at all phases of an immune response.
IL-18 Enhances IL-4 Production by Ligand-Activated NKT Lymphocytes: A Pro-Th2 Effect of IL-18 Exerted Through NKT Cells
Authors: Leite-de-Moraes Maria C. , Hameg Agathe , Pacilio Maria , Koezuka Yasuhiko , Taniguchi Masaru , Van Kaer Luc , Schneider Elke , Dy Michel , Herbelin André
Published: April 2014

NKT cells are a remarkably versatile population whose functional capacities are determined by cytokines present in their microenvironment. In this study, we provide evidence for a new immunoregulatory effect of the proinflammatory cytokine IL-18 on NKT cells. We found that IL-18, mainly known for its involvement in NK cell activation and in Th 1 immune responses, substantially enhanced IL-4 production as well as the percentage of IL-4+ cells among NKT lymphocytes activated by their specific ligand α-galactosylceramide (α-GalCer). The effect of IL-18 on IL-4 production by activated NKT cells took place both in vivo and in vitro and was not affected by IL-12 which increased IFN-γ secretion in the same conditions. We show that NKT cells are the main targets for IL-18-induced IL-4 production since it occurred neither in NKT-deficient mice nor after stimulation of Th2 lymphocytes. Finally, we provide evidence that the IL-4 promptly generated by NKT cells in response to IL-18 plus α-galactosylceramide in vivo can effectively contribute to the adaptive Th2 immune response by up-regulating the early activation marker CD69 on B cells. Our data support the notion that, in contrast to the exclusive IFN-γ inducer IL-12, IL-18 acts in a more subtle manner as a costimulatory factor in both pro-Th1 and pro-Th2 responses depending on the nature of the stimulation and the target cells.
Vaccination with Allergen-IL-18 Fusion DNA Protects Against, and Reverses Established, Airway Hyperreactivity in a Murine Asthma Model
Authors: Maecker Holden T. , Hansen Gesine , Walter David M. , DeKruyff Rosemarie H. , Levy Shoshana , Umetsu Dale T.
Published: April 2014

Vaccination with naked DNA encoding a specific allergen has been shown previously to prevent, but not reverse, the development of allergen-induced airway hyperresponsiveness (AHR). To enhance the effectiveness of DNA vaccine therapies and make possible the treatment of established AHR, we developed a DNA vaccination plasmid containing OVA cDNA fused to IL-18 cDNA. Vaccination of naive mice either with this fusion DNA construct or with an OVA cDNA-containing plasmid protected the mice from the subsequent induction of AHR. Protection from AHR correlated with increased IFN-γ production and reduced OVA-specific IgE production. The protection appeared to be mediated by IFN-γ and CD8+ cells because treatment of mice with neutralizing anti-IFN-γ mAb or with depleting anti-CD8 mAb abolished the protective effect. Moreover, vaccination of mice with preexisting AHR with the OVA-IL-18 fusion DNA, but not with the OVA cDNA plasmid, reversed established AHR, reduced allergen-specific IL-4, and increased allergen-specific IFN-γ production. Thus, combining IL-18 cDNA with OVA cDNA resulted in a vaccine construct that protected against the development of AHR, and that was unique among cDNA constructs in its capacity to reverse established AHR.
Quantifying the Frequency of Alloreactive T Cells In Vivo: New Answers to an Old Question
Authors: Suchin Elliot J. , Langmuir Peter B. , Palmer Ed , Sayegh Mohamed H. , Wells Andrew D. , Turka Laurence A.
Published: April 2014

Alloreactive T cell precursor frequency was measured in vivo using fluorescent dye labeling in combination with novel models based on lymphocyte activation and recovery. CFSE-labeled C57BL/6 (H-2b) spleen and lymph node cells were adoptively transferred to C57BL/6×DBA F1 (H-2b/d) recipients, a parent→F1 MHC mismatch in which only donor cells respond. Recipients were sacrificed at serial time points to assess engraftment efficiency, and the extent of donor cell activation and proliferation. These data were used to calculate alloreactive T cell frequencies that varied 30-fold (0.71 ± 0.31% to 21.05 ± 3.62%), depending upon whether it was assumed that all donor cells injected became established and were capable of responding, or that only those present at later time points (24–72 h) were available to respond. By measuring the number of cells established in the recipient 24 h after transfer, before proliferation, we calculated an in vivo alloreactive frequency of ∼7%. Using CD69 expression at 48 h to quantify activation, we found that 40–50% of the alloactivated CD4+ donor T cells do not divide. Studies of cotransferred congenic and allogeneic cells demonstrated that bystander proliferation does not occur. We conclude that accurate calculations of alloreactive precursor frequency must account for both proliferation and cell engraftment. When this is done, a high percentage of alloreactive T cells exists across an MHC mismatch, but not all alloreactive cells proliferate in vivo. Bystander proliferation is negligible, revealing exquisite specificity to the alloresponse. These data provide a novel approach to quantify alloreactive T cell responses during specific immunomodulatory strategies in vivo.
IL-7 and Not Stem Cell Factor Reverses Both the Increase in Apoptosis and the Decline in Thymopoiesis Seen in Aged Mice
Authors: Andrew Deborah , Aspinall Richard
Published: April 2014

Thymic atrophy is an age-associated decline in commitment to the T cell lineage considered to be associated with defective TCR β-chain rearrangement. Both IL-7 and stem cell factor (SCF) have dominant roles at this stage of triple negative (TN) thymocyte development. Because there is no age-associated decrease in the number of CD44+CD25−CD3−CD4−CD8− cells, this study investigated whether alterations in apoptosis within the TN pathway accounted for diminishing thymocyte numbers with age. Here we show significant age-associated increases in apoptotic TN thymocytes, specifically within CD44+CD25+ and CD44−CD25+ subpopulations, known to be the location of TCR β-chain rearrangement. IL-7 added to TN cultures established from old mice significantly both reduces apoptosis and increases the percentage of live cells within CD44+CD25+ and CD44−CD25+ subpopulations after 24 h, with prosurvival effects remaining after 5 days. SCF failed to demonstrate prosurvival effects in old or young cultures, and IL-7 and SCF together did not improve upon IL-7 alone. IL-7R expression did not decline with age, ruling out the possibility that the age-associated increase in apoptosis was attributed to reduced IL-7R expression. Compared with PBS, treatment of old mice with IL-7 produced significant increases in live TN cells. By comparison, treatment with SCF failed to increase live TN numbers, and IL-7 and SCF together failed to significantly improve thymopoiesis above that shown by IL-7 alone. Thus, treatment with IL-7 alone can reverse the age-associated defect in TN thymocyte development revealed by in vitro studies to be located at the stages of TCR β-chain rearrangement.
Autoimmune Intervention by CD154 Blockade Prevents T Cell Retention and Effector Function in the Target Organ
Authors: Howard Laurence M. , Miller Stephen D.
Published: April 2014

The CD40-CD154 interaction is an attractive target for therapeutic intervention in many autoimmune disorders, including multiple sclerosis. Previously, we showed that CD154 blockade both inhibited the onset of experimental autoimmune encephalomyelitis and blocked clinical disease progression (relapses) in mice with established disease. The mechanism of this protection is poorly understood. Because CD154 plays a role in Th1 development, its blockade has been thought to promote anti-inflammatory Th2 responses. However, these conclusions have primarily been based on extrapolated data from in vitro experiments, which may not accurately reflect the more complex events occurring in vivo. In this paper we determine how the immune response develops under the influence of therapeutic CD154 blockade in vivo. We demonstrate that anti-CD154 treatment does not alter the early expansion of Ag-specific T cells in secondary lymphoid organs or result in deviation to a Th2-dominant response. Interestingly, the late expansion and retention of Th1 cells in the lymph nodes were markedly reduced following immunization of Ab-treated mice, and this coincided with a recompartmentalization of these cells to the spleen. Most importantly, anti-CD154 treatment eliminated the retention/expansion of encephalitogenic Th1 cells, but not their entry into the CNS. These data indicate that a major mechanism by which CD154 blockade protects against autoimmune disease is by controlling the amplitude of acute phase Th1 responses in the draining lymph nodes and by preventing the sustained expansion of effector cells within the target organ.
Independent Regulation of Lymphocytic Choriomeningitis Virus-Specific T Cell Memory Pools: Relative Stability of CD4 Memory Under Conditions of CD8 Memory T Cell Loss
Authors: Varga Steven M. , Selin Liisa K. , Welsh Raymond M.
Published: April 2014

Infection of mice with a series of heterologous viruses causes a reduction of memory CD8+ T cells specific to viruses from earlier infections, but the fate of the virus-specific memory CD4+ T cell pool following multiple virus infections has been unknown. We have previously reported that the virus-specific CD4+ Th precursor (Thp) frequency remains stable into long-term immunity following lymphocytic choriomeningitis virus (LCMV) infection. In this study, we questioned whether heterologous virus infections or injection with soluble protein CD4 Ags would impact this stable LCMV-specific CD4+ Thp memory pool. Limiting dilution analyses for IL-2-producing cells and intracellular cytokine staining for IFN-γ revealed that the LCMV-specific CD4+ Thp frequency remains relatively stable following multiple heterologous virus infections or protein Ag immunizations, even under conditions that dramatically reduce the LCMV-specific CD8+ CTL precursor frequency. These data indicate that the CD4+ and CD8+ memory T cell pools are regulated independently and that the loss in CD8+ T cell memory following heterologous virus infections is not a consequence of a parallel loss in the memory CD4+ T cell population.
Role of Phosphatidylinositol 3-Kinase in Anti-IgM- and Anti-IgD-Induced Apoptosis in B Cell Lymphomas
Authors: Carey Gregory B. , Scott David W.
Published: April 2014

Cross-linking of surface Ig receptors with anti IgM (anti-μ heavy chain, anti-μ), but not anti-IgD (anti-δ heavy chain, anti-δ), Abs leads to growth arrest and apoptosis in several extensively characterized B cell lymphomas. By poorly understood mechanisms, both Igs transiently stimulate c-Myc protein expression. However, ultimately, only anti-μ causes a severe loss in c-Myc and a large induction of p27Kip1 protein expression. Because phosphatidylinositol 3-kinase (PI3K) has been established as a major modulator of cellular growth and survival, we investigated its role in mediating anti-Ig-stimulated outcomes. Herein, we show that PI3K pathways regulate cell cycle progression and apoptosis in the ECH408 B cell lymphoma. Anti-μ and anti-δ driven c-Myc protein changes precisely follow their effects on the PI3K effector, p70S6K. Upstream of p70S6K, signaling through both Ig receptors depresses PI3K pathway phospholipids below control with time, which is followed by p27Kip1 induction. Conversely, anti-δ, but not anti-μ stimulated PI3K-dependent phospholipid return to control levels by 4–8 h. Abrogation of the PI3K pathway with specific inhibitors mimics anti-μ action, potentiates anti-μ-induced cell death and, importantly, converts anti-δ to a death signal. Transfection with active PI3K kinase construct induces anti-μ resistance, whereas transfection with dominant negative PI3K augments anti-μ sensitivity. Our results show that prolonged disengagement of PI3K or down-regulation of its products by anti-μ (and not anti-δ) determines B cell fate.
Prostaglandin E2 Up-Regulates Macrophage-Derived Chemokine Production but Suppresses IFN-Inducible Protein-10 Production by APC
Authors: Kuroda Etsushi , Sugiura Tsutomu , Okada Kazumasa , Zeki Kazuya , Yamashita Uki
Published: April 2014

PGE2 has been known to suppress Th1 responses. We studied the role of PGE2 in two representative chemokines, macrophage-derived chemokine (MDC) and IFN-inducible protein-10, production by LPS- or CD40-stimulated spleen cells. The production of MDC, one of the ligands for CCR4 preferentially expressed on Th2, was enhanced in nonstimulated, LPS-, CD40-, or CD3-stimulated spleen cells by the pretreatment with PGE2, while the production of IFN-inducible protein-10, a representative ligand for CXC chemokine receptor 3 expressed on Th1, was suppressed. MDC production was also enhanced by IL-4, IL-5, and intracellular cAMP-elevating agents such as dibutyryl cAMP and 3-isobutyl-1-methylxanthine, and the effect of IL-4, IL-5, and PGE2 was additive. However, the pretreatment with IL-6, IL-10, or TGF-β, or the neutralization of IFN-γ or IL-12 had no effect on MDC production. B cells, macrophages, and dendritic cells were main producers of MDC, while T cells produced only a small amount of MDC. MDC production by B cells was equally stimulated by LPS and anti-CD40 Ab, while that by macrophages and dendritic cells was more markedly stimulated by anti-CD40 Ab, and PGE2 further enhanced MDC production by these stimulated cells. These results indicate that PGE2 regulates Th1/Th2-related chemokine production by B cells, macrophages, and dendritic cells, and that this is a new function of PGE2 for the regulation of Th2 immune responses at the induction and activation stages.
High-Avidity CTL Exploit Two Complementary Mechanisms to Provide Better Protection Against Viral Infection Than Low-Avidity CTL
Authors: Derby Michael A. , Alexander-Miller Martha A. , Tse Richard , Berzofsky Jay A.
Published: April 2014

Previously, we observed that high-avidity CTL are much more effective in vivo than low-avidity CTL in elimination of infected cells, but the mechanisms behind their superior activity remained unclear. In this study, we identify two complementary mechanisms: 1) high-avidity CTL lyse infected cells earlier in the course of a viral infection by recognizing lower Ag densities than those distinguished by low-avidity CTL and 2) they initiate lysis of target cells more rapidly at any given Ag density. Alternative mechanisms were excluded, including: 1) the possibility that low-avidity CTL might control virus given more time (virus levels remained as high at 6 days following transfer as at 3 days) and 2) that differences in efficacy might be correlated with homing ability. Furthermore, adoptive transfer of high- and low-avidity CTL into SCID mice demonstrated that transfer of a 10-fold greater amount of low-avidity CTL could only partially compensate for their decreased ability to eliminate infected cells. Thus, we conclude that high-avidity CTL exploit two complementary mechanisms that combine to prevent the spread of virus within the animal: earlier recognition of infected cells when little viral protein has been made and more rapid lysis of infected cells.
A New Regulatory Region of the IL-2 Locus That Confers Position-Independent Transgene Expression
Authors: Yui Mary A. , Hernández-Hoyos Gabriela , Rothenberg Ellen V.
Published: April 2014

Although the promoter/enhancer of the IL-2 gene mediates inducible reporter gene expression in vitro, it cannot drive consistent expression in transgenic mice. The location and existence of any regulatory elements that could open the IL-2 locus in vivo have remained unknown, preventing analysis of IL-2 regulation in developmental contexts. In this study, we report the identification of such a regulatory region, marked by novel DNase-hypersensitive sites upstream of the murine IL-2 promoter in unstimulated and stimulated T cells. Inclusion of most of these sites in an 8.4-kb IL-2 promoter green fluorescent protein transgene gives locus control region-like activity. Expression is efficient, tissue specific, and position independent. This transgene is expressed not only in peripheral T cells, but also in immature thymocytes and thymocytes undergoing positive selection, in agreement with endogenous IL-2 expression. In contrast, a 2-kb promoter green fluorescent protein transgene, lacking the new hypersensitive sites, is expressed in only a few founder lines, and expression is dysregulated in CD8+ cells. Thus, the 6.4 kb of additional upstream IL-2 sequence contains regulatory elements that provide integration site independence and differential regulation of transgene expression in CD8 vs CD4 cells.
The Integrity of the Ball-and-Socket Joint Between V and C Domains Is Essential for Complete Activity of a Humanized Antibody
Authors: Landolfi Nicholas F. , Thakur Archana B. , Fu Helen , Vásquez Max , Queen Cary , Tsurushita Naoya
Published: April 2014

AF2 is a high affinity murine Ab possessing potent neutralizing activity against human IFN-γ. In carrying out the modifications to humanize this Ab, we discovered that an initial version displayed affinity for IFN-γ that was slightly less than that of AF2, but exhibited IFN-γ-neutralizing activity that was severely diminished. Characterization via site-directed mutagenesis revealed that the majority of this loss in IFN-γ-neutralizing activity was due to altering the VH framework residue at position 11. VH position 11 is distal to the binding surface of the Ab; however, it, along with residues 110 and 112, have been identified as forming the socket of a molecular ball-and-socket joint between the V and C domains of the Ig Fab, which influences the elbow angle between these domains. To determine whether disrupting the structure of this joint was the basis for reduced IFN-γ-neutralizing capacity, we altered residue 148 of CH1, which with residue 149 comprises the corresponding ball portion of the joint. Changing this single CH1 domain residue diminished the ability of the Ab to neutralize IFN-γ to a level similar to that observed with the VH alteration. Thus, an intact ball-and-socket joint between the V and C domains in AF2 is required for potent neutralization of IFN-γ. These results suggest the importance of the elbow angle between Ig V and C domains in Ab activity, and support the hypothesis that this joint can be an important functional element of Ab structure.
The Interaction of FcαRI with IgA and Its Implications for Ligand Binding by Immunoreceptors of the Leukocyte Receptor Cluster
Authors: Wines Bruce D. , Sardjono Caroline T. , Trist Halina M. , Lay Chan-Sien , Hogarth P. Mark
Published: April 2014

This study defines the molecular basis of the FcαRI (CD89):IgA interaction, which is distinct from that of the other leukocyte Fc receptors and their Ig ligands. A comprehensive analysis using both cell-free (biosensor) and cell-based assays was used to define and characterize the IgA binding region of FcαRI. Biosensor analysis of mutant FcαRI proteins showed that residues Y35, Y81, and R82 were essential for IgA binding, and R52 also contributed. The role of the essential residues (Y35 and R82) was confirmed by analysis of mutant receptors expressed on the surface of mammalian cells. These receptors failed to bind IgA, but were detected by the mAb MY43, which blocks IgA binding to FcαRI, indicating that its epitope does not coincide with these IgA binding residues. A homology model of the ectodomains of FcαRI was generated based on the structures of killer Ig-like receptors, which share 30–34% identity with FcαRI. Key structural features of killer Ig-like receptors are appropriately reproduced in the model, including the structural conservation of the interdomain linker and hydrophobic core (residues V17, V97, and W183). In this FcαRI model the residues forming the IgA binding site identified by mutagenesis form a single face near the N-terminus of the receptor, distinct from other leukocyte Fc receptors where ligand binding is in the second domain. This taken together with major differences in kinetics and affinity for IgA:FcαRI interaction that were observed depending on whether FcαRI was immobilized or in solution suggest a mode of interaction unique among the leukocyte receptors.
NK1.1+ Cells and Murine Cytomegalovirus Infection: What Happens In Situ?
Authors: Andrews Daniel M. , Farrell Helen E. , Densley Eloise H. , Scalzo Anthony A. , Shellam Geoffrey R. , Degli-Esposti Mariapia A.
Published: April 2014

NK cells mediate early host defense against viral infection. In murine CMV (MCMV) infection NK cells play a critical role in controlling viral replication in target organs, such as spleen and liver. Until now it has not been possible to directly examine the role of NK cells in MCMV-induced inflammation in situ due to the inability to stain specifically for NK cells in infected tissues. In this study, we describe a method of in vivo fixation, resulting in the first identification of NK cells in situ using NK1.1 as the marker. Using this method, we characterize the NK1.1+ cellular component of the inflammatory response to wild-type MCMV in the spleen, liver, and lung of genetically susceptible and resistant mice following i.p. infection. This study provides the first in situ description of the cellular response mediated specifically by NK cells following MCMV infection.
The Application of a Plasmid DNA Encoding IFN-α1 Postinfection Enhances Cumulative Survival of Herpes Simplex Virus Type 2 Vaginally Infected Mice
Authors: Härle Peter , Noisakran Sansanee , Carr Daniel J. J.
Published: April 2014

Using a hormonally induced susceptibility mouse model to investigate vaginal HSV type 2 (HSV-2) infection, a study was undertaken to determine the efficacy of a plasmid DNA encoding IFN-α1 introduced into the vaginal lumen postinfection (PI). Mice infected with HSV-2 intravaginally and treated intravaginally 24 h later with 100 μg DNA encoding IFN-α1 showed enhanced survival (10/15) in comparison to mice treated with 100 μg plasmid DNA vector alone (3/10) or vehicle (4/27). In contrast, mice receiving recombinant IFN-αA (5–500 U/vagina) 24 h PI showed no significant survival in comparison to the vehicle (saline)-treated group. The protective effect was time dependent in that mice receiving the IFN-α1 transgene 48 h PI succumbed at a rate similar to the plasmid DNA vector-treated group. The increase in cumulative survival elicited by the transgene corresponded with a reduction in viral replication and Ag expressed in the vaginal epithelium early (i.e., 3 days PI) during acute infection and replicating virus recovered in the spinal cord day 7 PI. By day 7 PI, HSV-2 glycoprotein B transcript expression was no longer detectable in vaginal tissue from the IFN-α1 transgene-treated group (0/8) compared with levels expressed in plasmid vector-treated controls (4/6 mice surveyed were positive). Collectively, these results suggest the application of DNA encoding type I IFN is an effective and alternative approach to currently prescribed therapies in controlling vaginal HSV-2 infection by antagonizing viral replication.
Activated Antigen-Specific CD8+ T Cells Persist in the Lungs Following Recovery from Respiratory Virus Infections
Authors: Hogan Robert J. , Usherwood Edward J. , Zhong Weimin , Roberts Alan D. , Dutton Richard W. , Harmsen Allen G. , Woodland David L.
Published: April 2014

The poor correlation between cellular immunity to respiratory virus infections and the numbers of memory CD8+ T cells in the secondary lymphoid organs suggests that there may be additional reservoirs of T cell memory to this class of infection. Here we identify a substantial population of Ag-specific T cells in the lung that persist for several months after recovery from an influenza or Sendai virus infection. These cells are present in high numbers in both the airways and lung parenchyma and can be distinguished from memory cell populations in the spleen and peripheral lymph nodes in terms of the relative frequencies among CD8+ T cells, activation status, and kinetics of persistence. In addition, these cells are functional in terms of their ability to proliferate, express cytolytic activity, and secrete cytokines, although they do not express constitutive cytolytic activity. Adoptive transfer experiments demonstrated that the long-term establishment of activated T cells in the lung did not require infection in the lung by a pathogen carrying the inducing Ag. The kinetics of persistence of Ag-specific CD8+ T cells in the lung suggests that they play a key role in protective cellular immunity to respiratory virus infections.
Differential Regulation of the Expression of CD95 Ligand, Receptor Activator of Nuclear Factor-κB Ligand (RANKL), TNF-Related Apoptosis-Inducing Ligand (TRAIL), and TNF-α During T Cell Activation
Authors: Wang Ruoxiang , Zhang Liying , Zhang Xiaoren , Moreno Jose , Luo Xunyi , Tondravi Mehrdad , Shi Yufang
Published: April 2014

Members of TNF superfamily are characterized by their ability to inflict apoptosis upon binding to their cognate receptors in a homotrimeric manner. These proteins are expressed on different cell types under various conditions. However, the mechanisms governing the expression of these molecules remain elusive. We have found that the TCR signal can elicit the expression of receptor activator of NF-κB ligand (RANKL), TNF-α, CD95L, and TNF-related apoptosis inducing ligand (TRAIL) in T cell hybridoma A1.1 cells, thus allowing us to examine the expression pattern of these molecules under precisely the same conditions. We have previously reported that CD95L expression requires both protein kinase C (PKC) translocation and Ca2+ mobilization and is inhibited by cyclosporin A, and dexamethasone. We demonstrate now that activation-induced expression of RANKL is mediated by Ca2+ mobilization. PKC activation does not induce RANKL expression nor does it synergize with the Ca2+ signal. Activation-induced RANKL expression is blocked by cyclosporin A, but not by dexamethasone. The expression of TNF, in contrast, is mediated by PKC, but not by Ca2+. TNF-α expression is not inhibited by cyclosporin A, but is sensitive to dexamethasone. A1.1 cells constitutively express TRAIL at low levels. Stimulation with anti-CD3 leads to an initial reduction and subsequent increase in TRAIL expression. TRAIL induction is not inhibited by cyclosporin A, but highly sensitive to dexamethasone. Therefore, expression of the TNF superfamily genes is regulated by distinct signals. Detailed understanding of the regulatory mechanisms could provide crucial information concerning the role of these molecules in the modulation of the immune system.