bluuebunny/crossref_metadata_2025 huggingface dataset:
Treatment with α-Galactosylceramide BeforeTrypanosoma cruziInfection Provides Protection or Induces Failure to Thrive
Authors: Duthie Malcolm S. , Kahn Stuart J.
Published: April 2014

Trypanosoma cruzi, a protozoan parasite, chronically infects many mammalian species and triggers a chronic inflammatory disease. Invariant Vα14 NK T (iNKT) cells are a regulatory subset of T cells that can contribute to protection against pathogens and to control of chronic inflammatory diseases. α-Galactosylceramide (α-GalCer) is an iNKT cell-specific glycolipid Ag: a single immunization with α-GalCer stimulates robust IFN-γ and IL-4 production by iNKT cells, while multiple immunizations stimulate IL-4 production, but limited IFN-γ production. We recently demonstrated that iNKT cells help control T. cruzi infection and affect the chronic Ab response. Therefore, α-GalCer treatment might be used to increase protection or decrease chronic inflammation during T. cruzi infection. In this report, we show that a single dose of α-GalCer before T. cruzi infection decreases parasitemia. This protection is independent of IL-12, but dependent upon iNKT cell IFN-γ. In addition, α-GalCer treatment of the IFN-γ−/− mice exacerbates parasitemia through IL-4 production. Furthermore, a multiple dose regimen of α-GalCer before T. cruzi infection does not lower parasitemia and, surprisingly, after parasitemia has resolved, causes poor weight gain. These data demonstrate that during T. cruzi infection glycolipids can be used to manipulate iNKT cell responses and suggest the possibility of developing glycolipid treatments that can increase protection and possibly decrease the chronic inflammatory pathology.
Generation of Biologically Active Angiostatin Kringle 1–3 by Activated Human Neutrophils
Authors: Scapini Patrizia , Nesi Lorella , Morini Monica , Tanghetti Elena , Belleri Mirella , Noonan Douglas , Presta Marco , Albini Adriana , Cassatella Marco A.
Published: April 2014

The contribution of polymorphonuclear neutrophils (PMN) to host defense and natural immunity extends well beyond their traditional role as professional phagocytes. In this study, we demonstrate that upon stimulation with proinflammatory stimuli, human PMN release enzymatic activities that, in vitro, generate bioactive angiostatin fragments from purified plasminogen. We also provide evidence that these angiostatin-like fragments, comprising kringle domain 1 to kringle domain 3 (kringle 1–3) of plasminogen, are generated as a byproduct of the selective proteolytic activity of neutrophil-secreted elastase. Remarkably, affinity-purified angiostatin kringle 1–3 fragments generated by neutrophils inhibited basic fibroblast growth factor plus vascular endothelial growth factor-induced endothelial cell proliferation in vitro, and both vascular endothelial growth factor-induced angiogenesis in the matrigel plug assay and fibroblast growth factor-induced angiogenesis in the chick embryo chorioallantoic membrane assay, in vivo. These results represent the first demonstration that biologically active angiostatin-like fragments can be generated by inflammatory human neutrophils. Because angiostatin is a potent inhibitor of angiogenesis, tumor growth, and metastasis, the data suggest that activated PMN not only act as potent effectors of inflammation, but might also play a critical role in the inhibition of angiogenesis in inflammatory diseases and tumors, by generation of a potent anti-angiogenic molecule.
Lipopolysaccharide-Dependent Prostaglandin E2 Production Is Regulated by the Glutathione-Dependent Prostaglandin E2 Synthase Gene Induced by the Toll-Like Receptor 4/MyD88/NF-IL6 Pathway
Authors: Uematsu Satoshi , Matsumoto Makoto , Takeda Kiyoshi , Akira Shizuo
Published: April 2014

Macrophages produce a large amount of PGE2 during inflammation. This lipid mediator modulates various immune responses. PGE2 acts on macrophages and inhibits production of cytokines such as TNF-α and IL-12. Membrane-bound glutathione-dependent PGE2 synthase (mPGES) has been shown to be a terminal enzyme of the cyclooxygenase-2-mediated PGE2 biosynthesis. Here we identified mPGES as a molecule that is induced by LPS in macrophages. The expression of mPGES was not induced by LPS in mice lacking Toll-like receptor 4 or MyD88. Furthermore, mice deficient in NF-IL6 showed neither induction of mPGES nor biosynthesis of PGE2 in response to LPS, indicating that mPGES expression in response to LPS is regulated by a Toll-like receptor 4/MyD88/NF-IL6-dependent signaling pathway. We generated mPGES-deficient mice and investigated the role of mPGES in vivo. The mice showed no augmentation of the PGE2 production in response to LPS. However, they were not impaired in the LPS-induced production of inflammatory cytokines and showed normal response to the LPS-induced shock. Thus, mPGES is critically involved in the biosynthesis of PGE2 induced by LPS, but is dispensable for the modulation of inflammatory responses.
Acute Renal Failure in Endotoxemia Is Caused by TNF Acting Directly on TNF Receptor-1 in Kidney
Authors: Cunningham Patrick N. , Dyanov Hristem M. , Park Pierce , Wang Jun , Newell Kenneth A. , Quigg Richard J.
Published: April 2014

Bacterial endotoxin (LPS) is responsible for much of the widespread inflammatory response seen in sepsis, a condition often accompanied by acute renal failure (ARF). In this work we report that mice deficient in TNFR1 (TNFR1−/−) were resistant to LPS-induced renal failure. Compared with TNFR1+/+ controls, TNFR1−/− mice had less apoptosis in renal cells and fewer neutrophils infiltrating the kidney following LPS administration, supporting these as mediators of ARF. TNFR1+/+ kidneys transplanted into TNFR1−/− mice sustained severe ARF after LPS injection, which was not the case with TNFR1−/− kidneys transplanted into TNFR1+/+ mice. Therefore, TNF is a key mediator of LPS-induced ARF, acting through its receptor TNFR1 in the kidney.
Signal-Regulatory Protein α-CD47 Interactions Are Required for the Transmigration of Monocytes Across Cerebral Endothelium
Authors: de Vries Helga E. , Hendriks Jerome J. A. , Honing Henk , de Lavalette Chantal Renardel , van der Pol Susanne M. A. , Hooijberg Erik , Dijkstra Christine D. , van den Berg Timo K.
Published: April 2014

Monocyte infiltration into inflamed tissue requires their initial arrest onto the endothelial cells (ECs), followed by firm adhesion and subsequent transmigration. Although several pairs of adhesion molecules have been shown to play a role in the initial adhesion of monocytes to ECs, the mechanism of transendothelial migration is poorly defined. In this study, we have investigated the role of signal-regulatory protein (SIRP)α-CD47 interactions in monocyte transmigration across brain ECs. CD47 expression was observed in vivo on cerebral endothelium of both control animals and animals suffering from experimental allergic encephalomyelitis. To investigate whether SIRPα-CD47 interactions are instrumental in the trafficking of monocytes across cerebral EC monolayers, in vitro assays were conducted in which the migration of monocytes, but not adhesion, was found to be effectively diminished by blocking SIRPα and CD47 on monocytes and ECs, respectively. In this process, SIRPα was found to interact solely with its counterligand CD47 on ECs. Overexpression of the CD47 molecule on brain ECs significantly enhanced monocytic transmigration, but did not affect adhesion. SIRPα-CD47-mediated transendothelial migration involved Gi protein activity, a known signaling component of CD47. Finally, cross-linking of CD47 on brain ECs induced cytoskeletal reorganization of the endothelium, a process that was Gi protein independent. These data provide the first evidence that the interaction of CD47 with its monocytic counterligand SIRPα is of importance in the final step of monocyte trafficking into the brain, a critical event in the development of neuroinflammatory diseases.
Exposure to a Dysfunctional Glucocorticoid Receptor from Early Embryonic Life Programs the Resistance to Experimental Autoimmune Encephalomyelitis Via Nitric Oxide-Induced Immunosuppression
Authors: Marchetti Bianca , Morale Maria C. , Brouwer Jantien , Tirolo Cataldo , Testa Nuccio , Caniglia Salvo , Barden Nicholas , Amor Sandra , Smith Paul A. , Dijkstra Christine D.
Published: April 2014

Glucocorticoid (GC) hormones play a central role in the bidirectional communication between the neuroendocrine and the immune systems and exert, via GC receptors (GR), potent immunosuppressive and anti-inflammatory effects. In this study, we report that GR deficiency of transgenic mice expressing GR antisense RNA from early embryonic life has a dramatic impact in programming the susceptibility to experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. GR deficiency renders mice resistant to myelin oligodendrocyte glycoprotein-induced EAE, and such mice do not develop clinical or histological signs of disease compared with EAE-susceptible wild-type mice. Resistance to EAE in GR-deficient mice is associated not with endogenous GC levels, but with a significant reduction in spleen and lymph node cell proliferation. The use of NO inhibitors in vitro indicates that NO is the candidate immunosuppressor molecule. GR-deficient mice develop 3- to 6-fold higher nitrite levels in the periphery and are resistant to NO inhibition by GCs. Specific inhibition of NO production in vivo by treatment with the inducible NO synthase inhibitor, l-N6-(1-iminoethyl)-lysine, suppressed circulating nitrites, increased myelin oligodendrocyte glycoprotein-specific cell proliferation, and rendered GR-deficient mice susceptible to EAE. Thus, life-long GR deficiency triggers inducible NO synthase induction and NO generation with consequent down-regulation of effector cell proliferation. These findings identify a novel link among GR, NO, and EAE susceptibility and highlight NO as critical signaling molecule in bidirectional communication between the hypothalamic-pituitary-adrenocortical axis and the immune system.
Lipopolysaccharide-Induced Apoptosis of Endothelial Cells and Its Inhibition by Vascular Endothelial Growth Factor
Authors: Munshi Neru , Fernandis Aaron Z. , Cherla Rama P. , Park In-Woo , Ganju Ramesh K.
Published: April 2014

Endothelial injury is a major manifestation of septic shock induced by LPS. Recently, LPS was shown to induce apoptosis in different types of endothelial cells. In this study, we observed that pretreatment with vascular endothelial growth factor (VEGF), a known cell survival factor, blocked LPS-induced apoptosis in endothelial cells. We then further defined this LPS-induced apoptotic pathway and its inhibition by VEGF. We found that LPS treatment increased caspase-3 and caspase-1 activities and induced the cleavage of focal adhesion kinase. LPS also augmented expression of the pro-apoptotic protein Bax and the tumor suppressor gene p53. The pro-apoptotic Bax was found to translocate to the mitochondria from the cytosol following stimulation with LPS. Pretreatment of endothelial cells with VEGF inhibited the induction of both Bax and p53 as well as the activation of caspase-3. These data suggest that VEGF inhibits LPS-induced endothelial apoptosis by blocking pathways that lead to caspase activation.
CD4 and CD8 T Cells in Susceptibility/Protection to Collagen-Induced Arthritis in HLA-DQ8-Transgenic Mice: Implications for Rheumatoid Arthritis
Authors: Taneja Veena , Taneja Neelam , Paisansinsup Tawatchai , Behrens Marshall , Griffiths Marie , Luthra Harvinder , David Chella S.
Published: April 2014

To investigate the role of CD4 and CD8 T cells in arthritis, we generated transgenic mice deficient in CD4 and CD8 molecules expressing RA-susceptible gene HLA-DQ8. DQ8·CD4−/− mice were resistant to developing collagen-induced arthritis (CIA). However, DQ8·CD8−/− mice developed CIA with increased incidence and more severity than DQ8 mice. Both DQ8·CD8−/− and DQ8 mice produced rheumatoid factor. In addition, DQ8·CD8−/− mice produced antinuclear Abs. The B cell compartment and expression of DQ8 were normal in all the strains, although frequency of cells expressing DQ8 was less in CD4−/− mice. An increased frequency of CD3+ double-negative (DN) T cells was found in DQ8·CD8−/− compared with DQ8·CD4−/− and DQ8 mice. These CD3+ DN T cells produced high amounts of IL-10 in CD8-deficient mice. Analysis of cell division using a cell cycle tracking dye showed a higher rate of division of CD3+ and CD3+ DN T cells in DQ8·CD8−/− mice compared with DQ8·CD4−/− and DQ8 mice. Decreased apoptosis was seen in CIA-susceptible DQ8 and CD8-deficient mice, indicating a defect in activation-induced cell death. These observations suggest that CD4 cells are necessary for initiation of CIA in DQ8 mice. We hypothesize that CD8+ T cells are not capable of initiating CIA in DQ8-transgenic mice but may have a regulatory/protective effect.
HLA Class II Influences the Immune Response and Antibody Diversification to Ro60/Sjögren’s Syndrome-A: Heightened Antibody Responses and Epitope Spreading in Mice Expressing HLA-DR molecules
Authors: Paisansinsup Tawatchai , Deshmukh Umesh S. , Chowdhary Vaidehi R. , Luthra Harvinder S. , Fu Shu Man , David Chella S.
Published: April 2014

Abs to Ro/SSA Ags in the sera of patients with systemic lupus erythematosus and Sjögren’s syndrome are influenced by the HLA class II genes. To investigate the role of individual HLA class II genes in immune responses to human Ro60 (hRo60), mice lacking murine class II molecules and carrying either HLA genes DR2(DRB1*1502), DR3(DRB1*0301), DQ6(DQA1*0103/DQB1*0601), or DQ8(DQA1*0301/DQB1*0302), were immunized with rhRo60. The results show that hRo60 induces strong T and B cell responses in DR2, DR3, and DQ8 mice in comparison to weaker responses in DQ6 mice. In all mice, the majority of the dominant T cell epitopes were located in the amino portion (aa 61–185) and the carboxy portion (aa 381–525) of the hRo60 molecules. In contrast, the early dominant B cell epitopes were located in the middle and carboxy portion of the hRo60 molecule (aa 281–315 and 401–538). In DR2, DR3, and DQ8 mice, the B cell epitopes subsequently spread to the amino and carboxy portion of the hRo60 molecule but were limited to the middle and carboxy portion in DQ6 mice. The DR2 and DR3 mice produced the highest titers of immunoprecipitating Abs against hRo60 and native mouse Ro60. In addition, only DR2 mice exclusively produced immunoprecipitating Abs to native mouse Ro52 and Abs to mouse La by slot blot analysis, whereas in other strains of mice Abs to mouse La were cross-reactive with the immunogen. The results of the present study demonstrate the importance of HLA class II in controlling the immune responses to the Ro-ribonucleoprotein.
Lack of Antibody Production Following Immunization in Old Age: Association with CD8+CD28− T Cell Clonal Expansions and an Imbalance in the Production of Th1 and Th2 Cytokines
Authors: Saurwein-Teissl Maria , Lung Thomas L. , Marx Florentine , Gschösser Claudio , Asch Esther , Blasko Imrich , Parson Walther , Böck Günther , Schönitzer Diether , Trannoy Emanuelle , Grubeck-Loebenstein Beatrix
Published: April 2014

Although it is generally recognized that the function of the immune system declines with age, the nature of the underlying defects is still poorly understood. We now demonstrate the predominance of CD8+CD28− T cell clonal expansions in elderly persons who fail to produce specific Abs following influenza vaccination. These clones express effector cell markers and are mostly CD45RA+. When isolated and put into culture, they are unable to proliferate, but produce IFN-γ (but no IL-5) upon stimulation with anti-CD3 or autoantigen. These autoreactive CD8+ type 1 effector cells seem to trigger a Th1 polarization, as CD4+ T cells from elderly persons without in vivo Ab production produce Th1, but only low amounts of Th2 cytokines upon in vitro stimulation with PHA. Therefore, the increased occurrence of CD8+CD28− clonal expansions may be decisive for the development of immune deficiency in the elderly.
The Human T Cell Response to Myelin Oligodendrocyte Glycoprotein: A Multiple Sclerosis Family-Based Study
Authors: Koehler Niklas K. U. , Genain Claude P. , Giesser Barbara , Hauser Stephen L.
Published: April 2014

Myelin oligodendrocyte glycoprotein (MOG) is an encephalitogenic myelin protein and a likely autoantigen in human multiple sclerosis (MS). In this work, we describe the fine specificity and cytokine profile of T cell clones (TCC) directed against MOG in three nuclear families, comprised of four individuals affected with MS and their HLA-identical siblings. TCC were generated from PBMC by limiting dilution against a mixture of eleven 20-mer overlapping peptides corresponding to the encephalitogenic extracellular domain of human MOG (aa 1–120). The frequency of MOG peptide-reactive T cells was surprisingly high (range, 1:400 to 1:3,000) and, unexpectedly, cloning efficiencies were highest at low seeding densities of 102 or 103 PBMC per well. A total of 235 MOG peptide-reactive TCC were produced, all of which were CD4+CD8−TCRαβ+TCRγδ−. All 11 MOG peptides were recognized by the TCC, and different epitopes of MOG appeared to be immunodominant in the HLA-identical siblings. The patterns of cytokine secretion by TCC from single individuals were generally similar. The healthy individuals exhibited Th2-, Th0-, and T regulatory cell 1-like cytokine profiles, whereas TCC from one sibling with MS had a striking Th1-like phenotype, producing high levels of IFN-γ and TNF-α, and low IL-4 levels. Thus, MOG-reactive T cells appear to constitute an important part of the natural T cell repertoire, a finding that could contribute to the development of autoimmunity to this protein.
Deletion of p21 (WAF-1/Cip1) Does Not Induce Systemic Autoimmunity in Female BXSB Mice
Authors: Lawson Brian R. , Kono Dwight H. , Theofilopoulos Argyrios N.
Published: April 2014

Cell cycle, apoptosis, and replicative senescence are all influenced by the cyclin-dependent kinase inhibitor, p21. It was previously reported that deletion of p21 in 129/Sv × C57BL/6 mixed genetic background mice induced a severe lupus-like disease, almost exclusively in females. However, we did not confirm this finding in an independently derived stock of 129/Sv × C57BL/6 p21−/− mice. To further address this discrepancy, we examined the effects of p21 deletion in BXSB female mice that develop late-life, mild lupus-like disease. Survival, polyclonal Igs, anti-chromatin Abs, and kidney histopathology in these mice were unremarkable and identical to wild-type littermates for up to 14 mo of age. We conclude that p21 deficiency does not promote autoimmunity even in females of a predisposed strain. The findings indicate that the use of mixed background 129/Sv × C57BL/6 mice to study effects of gene deletions in systemic autoimmunity may be confounded by the genetic heterogeneity of this cross. We suggest that studies addressing gene deletion effects in systemic autoimmunity should use sufficiently backcrossed mice to attain genetic homogeneity, include wild-type littermate controls, and preferentially use congenic inbred strains with late-life lupus predisposition to emulate the polygenic nature of this disease.
Characterization of CD4+ CTLs Ex Vivo
Authors: Appay Victor , Zaunders John J. , Papagno Laura , Sutton Julian , Jaramillo Angel , Waters Anele , Easterbrook Philippa , Grey Pat , Smith Don , McMichael Andrew J. , Cooper David A. , Rowland-Jones Sarah L. , Kelleher Anthony D.
Published: April 2014

The cytotoxic potential of CD8+ T cells and NK cells plays a crucial role in the immune response to pathogens. Although in vitro studies have reported that CD4+ T cells are also able to mediate perforin-mediated killing, the in vivo existence and relevance of cytotoxic CD4+ T cells have been the subject of debate. Here we show that a population of CD4+ perforin+ T cells is present in the circulation at low numbers in healthy donors and is markedly expanded in donors with chronic viral infections, in particular HIV infection, at all stages of the disease, including early primary infection. Ex vivo analysis shows that these cells have cytotoxic potential mediated through the release of perforin. In comparison with more classical CD4+ T cells, this subset displays a distinct surface phenotype and functional profile most consistent with end-stage differentiated T cells and include Ag experienced CD4+ T cells. The existence of CD4+ cytotoxic T cells in vivo at relatively high levels in chronic viral infection suggests a role in the immune response.
T Cell Responses to an HLA-B*07-Restricted Epitope on the Dengue NS3 Protein Correlate with Disease Severity
Authors: Zivna Iva , Green Sharone , Vaughn David W. , Kalayanarooj Siripen , Stephens Henry A. F. , Chandanayingyong Dasnayanee , Nisalak Ananda , Ennis Francis A. , Rothman Alan L.
Published: April 2014

Dengue hemorrhagic fever (DHF), the severe manifestation of dengue virus (DV) infection characterized by plasma leakage, is more common in secondary DV infections in previously infected individuals and is associated with high levels of immune activation. To determine the Ag specificity of this immune response, we studied the response to an HLA-B*07-restricted T cell epitope, residues 221–232 of the DV NS3 protein, in 10 HLA-B*07+ Thai children who were studied during and after acute DV infections. Peptide-specific T cells were detected in 9 of 10 subjects. The frequency of peptide-specific T cells was higher in subjects who had experienced DHF than in those who had experienced DF. We also detected peptide-specific T cells in PBMC obtained at the time of the acute DV infection in 2 of 5 subjects. These data suggest that the NS3 (221–232) epitope is an important target of CD8+ T cells in secondary DV infection and that the activation and expansion of DV-specific T cells is greater in subjects with DHF than in those with dengue fever. These findings support the hypothesis that activation of DV-specific CD8+ T cells plays an important role in the pathogenesis of DHF.
Cutting Edge: Internalization of Transduced E-Selectin by Cultured Human Endothelial Cells: Comparison of Dermal Microvascular and Umbilical Vein Cells and Identification of a Phosphoserine-Type Di-leucine Motif
Authors: Kluger Martin S. , Shiao Stephen L. , Bothwell Alfred L. M. , Pober Jordan S.
Published: April 2014

Persistent E-selectin expression on human dermal microvascular endothelial cells (HDMEC), believed to mediate skin-specific T cell homing, results from a slow rate of surface protein internalization after cytokine induction. Following transduction of unactivated HDMEC with E-selectin cDNA, the rate of internalization was largely independent of increasing levels of surface protein expression, leading to prolonged t1/2 values of over 4 h, comparable to that observed following cytokine induction. In HUVEC, the rate of internalization increased with surface expression level, leading to an essentially constant t1/2 of under 2 h. Thus, the internalization process rather than cytokine responsiveness or E-selectin structure underlies the difference in endothelial cell behavior. Mutational analysis of the cytoplasmic region demonstrated a role for a di-leucine-type motif involving I588 and L589 but not for a putative tyrosine-type motif. Control of E-selectin surface expression appears to be phosphoserine dependent, since alanine but not aspartic acid substitution for S581 slows E-selectin internalization.
Cutting Edge: Attenuated Experimental Autoimmune Encephalomyelitis in Eta-1/Osteopontin-Deficient Mice
Authors: Jansson Marianne , Panoutsakopoulou Vily , Baker Jessica , Klein Ludger , Cantor Harvey
Published: April 2014

Recent studies indicate that early T lymphocyte activation 1 (Eta-1), also known as osteopontin, is a cytokine contributing to the development of Th1 immunity. In the present report, the role of Eta-1 in experimental autoimmune encephalomyelitis (EAE), a disease associated with Th1 immunity, was examined by analysis of disease progression in Eta-1-deficient (Eta-1−/−) mice. Although incidence and onset of peptide-induced EAE were found to be similar in Eta-1−/− and Eta-1+/+ mice, Eta-1−/− mice displayed significantly lower mean maximal clinical score and faster recovery without spontaneous relapses. Accordingly, decreased inflammatory infiltration and demyelination were observed in the spinal cords of Eta-1−/− mice. Furthermore, in comparison to Eta-1+/+, Eta-1−/− CD4+ T cells had reduced expression of IFN-γ and TNF-α upon ex vivo restimulation. Taken together, these results suggest that Eta-1 may sustain autoimmune responses by assisting in maintenance of Th1 immunity during EAE.
Transitional B Lymphocyte Subsets Operate as Distinct Checkpoints in Murine Splenic B Cell Development
Authors: Su Thomas T. , Rawlings David J.
Published: April 2014

Signaling through the Ag receptor is required for peripheral B lymphocyte maturation and maintenance. Defects in components of the B cell receptor (BCR) signalosome result in developmental blocks at the transition from immature (heat-stable Ag (HSA)high) to mature (HSAlow) B cells. Recent studies have subdivided the immature, or transitional, splenic B cells into two subsets, transitional 1 (T1) and transitional 2 (T2) cells. T1 and T2 cells express distinct surface markers and are located in distinct anatomic locations. In this report, we evaluated the BCR signaling capacity of T1 and T2 B cell subsets. In response to BCR engagement, T2 cells rapidly entered cell cycle and resisted cell death. In contrast, T1 cells did not proliferate and instead died after BCR stimulation. Correlating with these results, T2 cells robustly induced expression of the cell cycle regulator cyclin D2 and the antiapoptotic factors A1/Bfl-1 and Bcl-xL and exhibited activation of Akt. In contrast, T1 cells failed to up-regulate these markers. BCR stimulation of T2 cells also led to down-regulation of CD21 and CD24 (HSA) expression, resulting in a mature B cell phenotype. In addition, T2 cells from Bruton’s tyrosine kinase-deficient Xid mice failed to generate these proliferative and survival responses, suggesting a requirement for the BCR signalosome specifically at the T2 stage. Taken together, these data clearly demonstrate that T2 immature B cells comprise a discrete developmental subset that mediates BCR-dependent proliferative, prosurvival, and differentiation signals. Their distinct BCR-dependent responses suggest unique roles for T1 vs T2 cells in peripheral B cell selection.
The Dendritic Cell-Specific Adhesion Receptor DC-SIGN Internalizes Antigen for Presentation to T Cells
Authors: Engering Anneke , Geijtenbeek Teunis B. H. , van Vliet Sandra J. , Wijers Mietske , van Liempt Ellis , Demaurex Nicolas , Lanzavecchia Antonio , Fransen Jack , Figdor Carl G. , Piguet Vincent , van Kooyk Yvette
Published: April 2014

Dendritic cells (DCs) capture Ags or viruses in peripheral tissue to transport them to lymphoid organs to induce cellular T cell responses. Recently, a DC-specific C-type lectin was identified, DC-specific ICAM-grabbing non-integrin (DC-SIGN), that functions as cell adhesion receptor mediating both DC migration and T cell activation. DC-SIGN also functions as an HIV-1R that captures HIVgp120 and facilitates DC-induced HIV transmission of T cells. Internalization motifs in the cytoplasmic tail of DC-SIGN hint to a function of DC-SIGN as endocytic receptor. In this study we demonstrate that on DCs DC-SIGN is rapidly internalized upon binding of soluble ligand. Mutating a putative internalization motif in the cytoplasmic tail reduces ligand-induced internalization. Detailed analysis using ratio fluorescence imaging and electron microscopy showed that DC-SIGN-ligand complexes are targeted to late endosomes/lysosomes. Moreover, ligands internalized by DC-SIGN are efficiently processed and presented to CD4+ T cells. The distinct pattern of expression of C-type lectins on DCs in situ and their nonoverlapping Ag recognition profile hint to selective functions of these receptors to allow a DC to recognize a wide variety of Ags and to process these to induce T cell activation. These data point to a novel function of the adhesion receptor DC-SIGN as an efficient DC-specific Ag receptor that can be used as a target to induce viral and antitumor immunity.
Receptor-Facilitated Antigen Presentation Requires the Recruitment of B Cell Linker Protein to Igα
Authors: Siemasko Karyn , Skaggs Brian J. , Kabak Shara , Williamson Edward , Brown Bruce K. , Song Wenxia , Clark Marcus R.
Published: April 2014

Ags that cross-link the B cell Ag receptor are preferentially and rapidly delivered to the MHC class II-enriched compartment for processing into peptides and subsequent loading onto MHC class II. Proper sorting of Ag/receptor complexes requires the recruitment of Syk to the phosphorylated immunoreceptor tyrosine-based activation motif tyrosines of the B cell Ag receptor constituent Igα. We postulated that the Igα nonimmunoreceptor tyrosine-based activation motif tyrosines, Y176 and Y204, contributed to receptor trafficking. Igα(YΔF176,204)/Igβ receptors were targeted to late endosomes, but were excluded from the vesicle lumen and could not facilitate the presentation of Ag to T cells. Subsequent analysis demonstrated that phosphorylation of Y176/Y204 recruited the B cell linker protein, Vav, and Grb2. Reconstitution of Igα(YΔF176,204)/Igβ with the B cell linker protein rescued both receptor-facilitated Ag presentation and entry into the MHC class II-enriched compartment. Thus, aggregation accelerates receptor trafficking by recruiting two separate signaling modules required for transit through sequential checkpoints.
Hyperproliferative Response of a Monoclonal Memory CD8 T Cell Population Is Characterized by an Increased Frequency of Clonogenic Precursors
Authors: Arpin Christophe , Angelov Georgi , Walzer Thierry , Tomkowiak Martine , Belœil Laurent , Marvel Jacqueline
Published: April 2014

Strong memory T cell responses result partly from the selection of Ag-specific clones during immunization. In this study, we show that a monoclonal CD8 T cell population expressing a unique TCR is heterogeneous in terms of clonogenic potential following activation under optimal conditions. More importantly, the frequency of clonogenic cells is strongly increased among Ag-experienced cells, indicating that these cells were either generated or selected during the in vivo primary response. Moreover, strong proliferative responses of primed cells result from this enhanced frequency, as proliferating naive and primed cells display the same cycling parameters, i.e., lag time and intermitotic interval. Hence, these results suggest that the clonogenic potential of individual cells is imprinted before Ag encounter and that clonogenic precursors are selected or generated following in vivo activation.
Efficient Delivery of T Cell Epitopes to APC by Use of MHC Class II-Specific Troybodies
Authors: Lunde Elin , Western Karoline H. , Rasmussen Ingunn B. , Sandlie Inger , Bogen Bjarne
Published: April 2014

A major objective in vaccine development is the design of reagents that give strong, specific T cell responses. We have constructed a series of rAb with specificity for MHC class II (I-E). Each has one of four different class II-restricted T cell epitopes genetically introduced into the first C domain of the H chain. These four epitopes are: 91–101 λ2315, which is presented by I-Ed; 110–120 hemagglutinin (I-Ed); 323–339 OVA (I-Ad); and 46–61 hen egg lysozyme (I-Ak). We denote such APC-specific, epitope-containing Ab “Troybodies.” When mixed with APC, all four class II-specific Troybodies were ∼1,000 times more efficient at inducing specific T cell activation in vitro compared with nontargeting peptide Ab. Furthermore, they were 1,000–10,000 times more efficient than synthetic peptide or native protein. Conventional intracellular processing of the Troybodies was required to load the epitopes onto MHC class II. Different types of professional APC, such as purified B cells, dendritic cells, and macrophages, were equally efficient at processing and presenting the Troybodies. In vivo, class II-specific Troybodies were at least 100 times more efficient at targeting APC and activating TCR-transgenic T cells than were the nontargeting peptide Ab. Furthermore, they were 100–100,000 times more efficient than synthetic peptide or native protein. The study shows that class II-specific Troybodies can deliver a variety of T cell epitopes to professional APC for efficient presentation, in vitro as well as in vivo. Thus, Troybodies may be useful as tools in vaccine development.
Correlation of Tissue Distribution, Developmental Phenotype, and Intestinal Homing Receptor Expression of Antigen-Specific B Cells During the Murine Anti-Rotavirus Immune Response
Authors: Youngman Kenneth R. , Franco Manuel A. , Kuklin Nelly A. , Rott Lusijah S. , Butcher Eugene C. , Greenberg Harry B.
Published: April 2014

The intestinal homing receptor, α4β7, helps target lymphocytes to Peyer’s patches (PP) and intestinal lamina propria (ILP). We have previously shown that protective immunity to rotavirus (RV), an intestinal pathogen, resides in memory B cells expressing α4β7. In this study, using a novel FACS assay, we have directly studied the phenotype of B cells that express surface RV-specific Ig during the in vivo RV immune response. During primary infection, RV-specific B cells first appear as large IgD−B220lowα4β7− and α4β7+ cells (presumptive extrafollicular, Ab-secreting B cells), and then as large and small IgD−B220highα4β7− cells (presumptive germinal center B cells). The appearance of B cells with the phenotype of large IgD−B220lowα4β7+ cells in PP and most notably in mesenteric lymph nodes coincides with the emergence of RV-specific Ab-secreting cells (ASC) in the ILP. Thus, these B lymphocytes are good candidates for the migratory population giving rise to the RV-specific ASC in the ILP. RV-specific long-term memory B cells preferentially accumulate in PP and express α4β7. Nine months after infection most RV-specific IgA ASC are found in PP and ILP and at lower frequency in bone marrow and spleen. This study is the first to follow changes in tissue-specific homing receptor expression during Ag-specific B cell development in response to a natural host, tissue-specific pathogen. These results show that α4β7 is tightly regulated during the Ag-specific B cell response to RV and is expressed concurrently with the specific migration of memory and effector B cells to intestinal tissues.
Evidence for the Extrathymic Origin of Intestinal TCRγδ+ T Cells in Normal Rats and for an Impairment of This Differentiation Pathway in BB Rats
Authors: Ramanathan Sheela , Marandi Leili , Poussier Philippe
Published: April 2014

The BB rat lyp mutation, one of its diabetes susceptibility genes, is responsible for a 5-fold decrease in the number of peripheral TCRαβ+ T cells. In this study we show that TCRγδ+ T cells are virtually undetectable among splenic T cells and intestinal intraepithelial T lymphocytes (IEL) of BB rats, while they account for 3 and 30% of these two T cell populations, respectively, in normal animals. It has been shown that murine IEL expressing TCRγδ develop extrathymically. We determined whether this is the case in rats. Athymic radiation chimeras reconstituted with normal hemopoietic precursors were devoid of donor-derived TCRαβ+ T cells and TCRγδ+ splenocytes but contained a normal number of TCRγδ+ IEL, suggesting that in unmanipulated rats some of the TCRγδ+ IEL may have an extrathymic origin. This was further supported by the observation that RAG1 transcripts are present in IEL of unmanipulated animals. No T cells developed in chimeras reconstituted with BB hemopoietic precursors, demonstrating that the BB rat lyp mutation inhibits both intrathymic and extrathymic development of TCRγδ+ T cells.
Administration of an Antigen at a High Dose Generates Regulatory CD4+ T Cells Expressing CD95 Ligand and Secreting IL-4 in the Liver
Authors: Watanabe Tomohiro , Yoshida Masaru , Shirai Yasuhiko , Yamori Masashi , Yagita Hideo , Itoh Toshiyuki , Chiba Tsutomu , Kita Toru , Wakatsuki Yoshio
Published: April 2014

Ags administered orally at a high dose are absorbed in immunogenic forms and perfuse the liver, which raises a question regarding the relevance of hepatic lymphocyte activation to the systemic hyporesponsiveness against the ingested Ag. Oral administration of 100 mg of OVA to the mice led to massive cell death of OVA-specific (KJ1-26+) CD4+ T cells by Fas-Fas ligand (FasL)-mediated apoptosis in the liver, which was associated with the emergence of hepatic KJ1-26+CD4+ T cells expressing FasL. Hepatic CD4+ T cells in OVA-fed mice secreted large amounts of IL-4, IL-10, and TGF-β1 upon restimulation in vitro and inhibited T cell proliferation. Adoptive transfer of these hepatic CD4+ T cells to naive mice and subsequent antigenic challenge led to suppression of T cell proliferation as well as IgG Ab responses to OVA; this effect was mostly abrogated by a blocking Ab to FasL. i.p. administration of an Ag at a high dose also generated hepatic CD4+FasL+ T cells with similar cytokine profile as T cells activated by oral administration of Ags at a high dose. Finally, we did not see an increase in FasL+ cells in the hepatic CD4+Vβ8+ T cell subset of MRL/lpr/lpr mice given staphylococcal enterotoxin B, indicating the requirement for Fas-mediated signals. These hepatic CD4+FasL+ regulatory cells may explain the tolerogenic property of the liver and play roles in systemic hyporesponsiveness induced by an Ag administered at a high dose.
The Nonclassical Major Histocompatibility Complex Molecule Qa-2 Protects Tumor Cells from NK Cell- and Lymphokine-Activated Killer Cell-Mediated Cytolysis
Authors: Chiang Eugene Y. , Henson Maile , Stroynowski Iwona
Published: April 2014

The cytotoxic activity of NK cells is regulated by class I MHC proteins. Although much has been learned about NK recognition of class I autologous targets, the mechanisms of NK self-tolerance are poorly understood. To examine the role of a nonpolymorphic, ubiquitously expressed class Ib Ag, Q9, we expressed it on class I-deficient and NK-sensitive B78H1 melanoma. Presence of this Qa-2 family member on tumor cells partially protected targets from lysis by bulk lymphokine-activated killer (LAK) cells. H-2Kb-expressing B78H1 targets also reduced LAK cell activity, while H-2Db offered no protection. Importantly, blocking with F(ab′)2 specific for Q9 or removal of this GPI-attached molecule by phospholipase C cleavage restored killing to the level of vector-transfected cells. Experiments with LAK cells derived from H2b SCID and B6 mice established that NK1.1+TCR− NK and NK1.1+TCR+ LAK cells were the prevalent cytolytic populations inhibitable by Q9. Treatment of mice with poly(I:C) also resulted in generation of Q9-regulated splenic cytotoxicity. LAK cells from different mouse strains responded to Q9, suggesting that the protective effect of this molecule is not detectably influenced by Ly49 polymorphisms or the presence/absence of Q9 in NK-harboring hosts. We propose that Q9 expressed on melanoma cells serves as a ligand for yet unidentified NK inhibitory receptor(s) expressed on NK1.1+ NK/T cells.
Positive Effects of Glucocorticoids on T Cell Function by Up-Regulation of IL-7 Receptor α
Authors: Franchimont Denis , Galon Jérôme , Vacchio Melanie S. , Fan Samuel , Visconti Roberta , Frucht David M. , Geenen Vincent , Chrousos George P. , Ashwell Jonathan D. , O’Shea John J.
Published: April 2014

Despite the effects of glucocorticoids on immune function, relatively little is known about glucocorticoid-inducible genes and how their products may regulate lymphocyte function. Using DNA microarray technology to analyze gene expression in PBMC from healthy donors, we identified IL-7Rα as a glucocorticoid-inducible gene. This observation was confirmed at the mRNA and protein levels. Conversely, TCR signaling decreased IL-7Rα expression, and the relative strength of signaling between these two receptors determined the final IL-7Rα levels. The up-regulation of IL-7Rα by glucocorticoids was associated with enhanced IL-7-mediated signaling and function. Moreover, IL-7-mediated inhibition of apoptosis at increasing concentrations of glucocorticoids is consistent with enhanced cell sensitivity to IL-7 following glucocorticoid exposure. These observations provide a mechanism by which glucocorticoids may have a positive influence on T cell survival and function.
Functional Expression of the Chemokine Receptor CCR5 on Virus Epitope-Specific Memory and Effector CD8+ T Cells
Authors: Fukada Katsuhiko , Sobao Yuji , Tomiyama Hiroko , Oka Shinichi , Takiguchi Masafumi
Published: April 2014

Because the chemokine receptor CCR5 is expressed on Th1 CD4+ cells, it is important to investigate the expression and function of this receptor on other T cells involved in Th1 immune responses, such as Ag-specific CD8+ T cells, which to date have been only partially characterized. Therefore, we analyzed the expression and function of CCR5 on virus-specific CD8+ T cells identified by HLA class I tetramers. Multicolor flow cytometry analysis demonstrated that CCR5 is expressed on memory (CD28+CD45RA−) and effector (CD28−CD45RA− and CD28−CD45RA+) CD8+ T cells but not on naive (CD28+CD45RA+) CD8+ T cells. CCR5 expression was much lower on two effector CD8+ T cells than on memory CD8+ T cells. Analysis of CCR7 and CCR5 expression on the different types of CD8+ T cells showed that memory CD8+ T cells have three phenotypic subsets, CCR5+CCR7−, CCR5+CCR7+, and CCR5−CCR7+, while naive and effector CD8+ T cells have CCR5−CCR7+ and CCR5+CCR7− phenotypes, respectively. These results suggest the following sequence for differentiation of memory CD8+ T cells: CCR5−CCR7+→CCR5+CCR7+→CCR5+CCR7−. CCR5+CD8+ T cells effectively migrated in response to RANTES, suggesting that CCR5 plays a critical role in the migration of Ag-specific effector and differentiated memory CD8+ T cells to inflammatory tissues and secondary lymphoid tissues. This is in contrast to CCR7, which functions as a homing receptor in migration of naive and memory CD8+ T cells to secondary lymphoid tissues.
Antigen-Antibody Immune Complexes Empower Dendritic Cells to Efficiently Prime Specific CD8+ CTL Responses In Vivo
Authors: Schuurhuis Danita H. , Ioan-Facsinay Andreea , Nagelkerken Bas , van Schip Jolien J. , Sedlik Christine , Melief Cornelis J. M. , Verbeek J. Sjef , Ossendorp Ferry
Published: April 2014

Dendritic cells (DCs) require a maturation signal to acquire efficient CTL-priming capacity. In vitro FcγR-mediated internalization of Ag-Ab immune complexes (ICs) can induce maturation of DCs. In this study, we show that IC-induced DC maturation in vitro enables DCs to prime peptide-specific CD8+ CTLs in vivo, independently of CD4+ Th cells. Importantly, OVA/anti-OVA IC-treated DCs not only primed CD8+ CTLs to an exogenously loaded peptide nonrelated to OVA, but also efficiently primed CTLs against the dominant CTL epitope derived from the OVA Ag present in the ICs. Our studies show that ICs fulfill a dual role in priming of CD8+ CTL responses to exogenous Ags: enhancement of Ag uptake by DCs and activation of DCs, resulting in “license to kill.” These findings indicate that the presence of specific Abs can crucially affect the induction of cytotoxic cellular responses.
Tracking the Immunoregulatory Mechanisms Active During Allograft Tolerance
Authors: Sánchez-Fueyo Alberto , Weber Martina , Domenig Christoph , Strom Terry B. , Zheng Xin Xiao
Published: April 2014

Immunoregulatory mechanisms dependent on regulatory CD4+ T cells are believed to be critical in the maintenance of peripheral tolerance to allografts. However, a detailed characterization of the effects of these regulatory T cells has been hampered by the absence of a simple means to track and study them. In this work we provide evidence that in a murine model of islet transplantation the interactions between alloaggressive and regulatory T cells can be studied in vitro and in vivo at the single-cell level. The observations made in both an in vitro coculture system and an in vivo CFSE-based adoptive transfer model indicate that lymphocytes from tolerant allograft recipients 1) proliferate weakly to donor strain allogeneic cells but vigorously to third-party strain cells; and 2) suppress the proliferation of naive syngeneic CD4+ and CD8+ T cells to donor tissue in a cell dose- and Ag-specific manner. These effects depend on the presence of CD4+CD25+ T cells and are neutralized by anti-CTLA4 mAb or rIL-2. The principal effect of anti-CTLA4 is directed against the naive, not regulatory, T cell population. These results can be replicated in vivo by transferring lymphocyte populations into transplant recipients, proving that the graft-protecting actions of regulatory T cells are blunted by a rise in the number of allodestructive T cells (pool size model) and depend on the presence of CD4+CD25+ T cells and the integrity of the CTLA4/B7 pathway.
Evolution of Ig DNA Sequence to Target Specific Base Positions Within Codons for Somatic Hypermutation
Authors: Shapiro Gary S. , Aviszus Katja , Murphy James , Wysocki Lawrence J.
Published: April 2014

Ig variable (V) region genes are subjected to a somatic hypermutation process as B lymphocytes participate in immune reactions to protein Ags. Although little is known regarding the mechanism of mutagenesis, a consistent hierarchy of trinucleotide target preferences is evident. Analysis of trinucleotide regional distributions predicted and we now empirically confirm the surprising finding that the framework 2 region of κ V region genes is highly mutable despite its importance to the structural integrity and function of the Ab molecule. Interestingly, much of this mutability appears to be focused on the third codon position where synonymous substitutions are most likely to occur. We also observed a trend for high predicted mutability for codon positions 1 and 2 in complementarity-determining regions. Consequently, amino acid replacements should occur at a higher rate in complementarity-determining regions than in framework regions due to the distribution and subsequent targeting of microsequences by the mutation mechanism. Our results reveal a subtle tier of V region gene evolution in which DNA sequence has been molded to direct mutations to specific base positions within codons in a manner that minimizes damage and maximizes the benefits of the somatic hypermutation process.
Allelic Polymorphism Synergizes with Variable Gene Content to Individualize Human KIR Genotype
Authors: Shilling Heather G. , Guethlein Lisbeth A. , Cheng Nathalie W. , Gardiner Clair M. , Rodriguez Roberto , Tyan Dolly , Parham Peter
Published: April 2014

Killer Ig-like receptor (KIR) genes are a multigene family on human chromosome 19. KIR genes occur in various combinations on different haplotypes. Additionally, KIR genes are polymorphic. To examine how allelic polymorphism diversifies KIR haplotypes with similar or identical combinations of KIR genes, we devised methods for discriminating alleles of KIR2DL1, -2DL3, -3DL1, and -3DL2. These methods were applied to 143 individuals from 34 families to define 98 independent KIR haplotypes at the allele level. Three novel 3DL2 alleles and a chimeric 3DL1/3DL2 sequence were also identified. Among the A group haplotypes were 22 different combinations of 2DL1, 2DL3, 3DL1, and 3DL2 alleles. Among the B group haplotypes that were unambiguously determined were 15 distinct haplotypes involving 9 different combinations of KIR genes. A and B haplotypes both exhibit strong linkage disequilibrium (LD) between 2DL1 and 2DL3 alleles, and between 3DL1 and 3DL2 alleles. In contrast, there was little LD between the 2DL1/2DL3 and 3DL1/3DL2 pairs that define the two halves of the KIR gene complex. The synergistic combination of allelic polymorphism and variable gene content individualize KIR genotype to an extent where unrelated individuals almost always have different KIR types. This level of diversity likely reflects strong pressure from pathogens on the human NK cell response.