bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of NF-κB in TNF-Related Apoptosis-Inducing Ligand (TRAIL)-Induced Apoptosis of Melanoma Cells
Authors: Franco Agustin V. , Zhang Xu Dong , Van Berkel Elisabeth , Sanders Jayne E. , Zhang Xi Yi , Thomas Wayne D. , Nguyen Tam , Hersey Peter
Published: April 2014

Previous studies have shown that activation of NF-κB can inhibit apoptosis induced by a number of stimuli. It is also known that TNF-related apoptosis-inducing ligand (TRAIL) can activate NF-κB through the death receptors TRAIL-R1 and TRAIL-R2, and decoy receptor TRAIL-R4. In view of these findings, we have investigated the extent to which activation of NF-κB may account for the variable responses of melanoma lines to apoptosis induced by TRAIL and other TNF family members. Pretreatment of the melanoma lines with the proteasome inhibitor N-acetyl-l-leucinyl-l-leucinyl-l-norleucinal (LLnL), which is known to inhibit activation of NF-κB, was shown to markedly increase apoptosis in 10 of 12 melanoma lines with death receptors for TRAIL. The specificity of results for inhibition of NF-κB activation was supported by an increase of TRAIL-induced apoptosis in melanoma cells transfected with a degradation-resistant IκBα. Furthermore, studies with NF-κB reporter constructs revealed that the resistance of melanoma lines to TRAIL-induced apoptosis was correlated to activation of NF-κB in response to TRAIL. TRAIL-resistant sublines that were generated by intermittent exposure to TRAIL were shown to have high levels of activated NF-κB, and resistance to TRAIL could be reversed by LLnL and by the superrepressor form of IκBα. Therefore, these results suggest that activation of NF-κB by TRAIL plays an important role in resistance of melanoma cells to TRAIL-induced apoptosis and further suggest that inhibitors of NF-κB may be useful adjuncts in clinical use of TRAIL against melanoma.
Papillomavirus-Like Particles Induce Acute Activation of Dendritic Cells
Authors: Lenz Petra , Day Patricia M. , Pang Yuk-Ying S. , Frye Stephan A. , Jensen Peter N. , Lowy Douglas R. , Schiller John T.
Published: April 2014

The role of viral structural proteins in the initiation of adaptive immune responses is poorly understood. To address this issue, we focused on the effect of noninfectious papillomavirus-like particles (VLPs) on dendritic cell (DC) activation. We found that murine bone marrow-derived dendritic cells (BMDCs) effectively bound and rapidly internalized bovine papillomavirus VLPs. Exposure to fully assembled VLPs of bovine papillomavirus, human papillomavirus (HPV)16 or HPV18, but not to predominately disordered HPV16 capsomers, induced acute phenotypic maturation of BMDCs. Structurally similar polyomavirus VLPs bound to the DC surface and were internalized, but failed to induce maturation. DCs that had incorporated HPV16 VLPs produced proinflammatory cytokines IL-6 and TNF-α; however, the release of these cytokines was delayed relative to LPS activation. Production of IL-12p70 by VLP-exposed DCs required the addition of syngeneic T cells or rIFN-γ. Finally, BMDCs pulsed with HPV16 VLPs induced Th1-dominated primary T cell responses in vitro. Our data provide evidence that DCs respond to intact papillomavirus capsids and that they play a central role in VLP-induced immunity. These results offer a mechanistic explanation for the striking ability of papillomavirus VLP-based vaccines to induce potent T and B cell responses even in the absence of adjuvant.
Three-Cell Interactions in T Cell-Mediated Suppression? A Mathematical Analysis of Its Quantitative Implications
Authors: León Kalet , Peréz Rolando , Lage Agustin , Carneiro Jorge
Published: April 2014

Aiming to further our understanding of T cell-mediated suppression, we investigate the plausibility of the hypothesis that regulatory T cells suppress other T cells (target cells), while both cells are conjugated with one APC. We use a mathematical model to analyze the proliferation inhibition scored during in vitro suppression assays. This model is a radical simplification of cell culture reality, assuming that thymidine incorporation is proportional to the number of target cells that would instantaneously form conjugates with APCs that are free of regulatory cells. According to this model the inhibition index should be mainly determined by the number of regulatory cells per APC and should be insensitive to the number of target cells. We reanalyzed several published data sets, confirming this expectation. Furthermore, we demonstrate that the instantaneous inhibition index has an absolute limit as a function of the number of regulatory cells per APC. By calculating this limit we find that the model can explain the data under two non-mutually exclusive conditions. First, only ∼15% of APCs used in the suppression assays form conjugates with T cells. Second, the growth of the regulatory cell population depends on the target cells, such that the number of regulatory cells per APC increases when they are cocultured with target cells and overcomes its limit. However, if neither of these testable conditions is fulfilled, then one could conclude that suppression in vitro does not require the formation of multicellular conjugates.
Defined Flanking Spacers and Enhanced Proteolysis Is Essential for Eradication of Established Tumors by an Epitope String DNA Vaccine
Authors: Velders Markwin P. , Weijzen Sanne , Eiben Gretchen L. , Elmishad Amira G. , Kloetzel Peter-M. , Higgins Terry , Ciccarelli Richard B. , Evans Mererid , Man Stephen , Smith Larry , Kast W. Martin
Published: April 2014

Loss of immunogenic epitopes by tumors has urged the development of vaccines against multiple epitopes. Recombinant DNA technologies have opened the possibility to develop multiepitope vaccines in a relatively rapid and efficient way. We have constructed four naked DNA-based multiepitope vaccines, containing CTL, Th cell, and B cell epitopes of the human papillomavirus type 16. Here we show that gene gun-mediated vaccination with an epitope-based DNA vaccine protects 100% of the vaccinated mice against a lethal tumor challenge. The addition of spacers between the epitopes was crucial for the epitope-induced tumor protection, as the same DNA construct without spacers was significantly less effective and only protected 50% of the mice. When tested for therapeutic potential, only the epitope construct with defined spacers significantly reduced the size of established tumors, but failed to induce tumor regression. Only after targeting the vaccine-encoded protein to the protein degradation pathway by linking it to ubiquitin, the vaccine-induced T cell-mediated eradication of 100% of 7-day established tumors in mice. The finding that defined flanking sequences around epitopes and protein targeting dramatically increased the efficacy of epitope string DNA vaccines against established tumors will be of importance for the further development of multiepitope DNA vaccines toward clinical application.
Engineering of Macrophages to Produce IFN-γ in Response to Hypoxia
Authors: Carta Luca , Pastorino Sandra , Melillo Giovanni , Bosco Maria C. , Massazza Stefano , Varesio Luigi
Published: April 2014

Activation of murine macrophages (Mφ) requires the collaboration of signals derived from the immune system and the environment. In this study, we engineered a murine Mφ cell line to become activated in response to an environmental signal, hypoxia, as the sole stimulus. Hypoxia is a condition of low oxygen tension, occurring in several pathological tissues, which acts in synergy with IFN-γ to induce full Mφ activation. We transfected the ANA-1 murine Mφ cell line with a construct containing the IFN-γ gene controlled by a synthetic promoter inducible by hypoxia (HRE3x-Tk), and we characterized the cellular and molecular biology of the engineered Mφ under normoxia or hypoxia. Engineered Mφ in normoxia expressed basal levels of IFN-γ mRNA and protein that were strongly augmented by shifting the cells to hypoxia. Furthermore, they responded to the synthesized IFN-γ with induction of IFN-responsive factor-1 and 2′-5′-oligoadenylate synthase expression. Under normoxic conditions, the engineered Mφ had a significant constitutive level of Ia Ags and Fc receptors. Hypoxia induced further augmentation of Ia and Fc expression. Finally, hypoxia induced inducible NO synthase expression, and subsequent reoxygenation led to the production of NO. In conclusion, the engineered Mφ, which produce IFN-γ in an inducible manner, express new biochemical and functional properties in response to low oxygen environment as the sole stimulus, thereby circumventing the need for costimulation by other immune system-derived signals.
HIV-1 gp120 Stimulates the Production of β-Chemokines in Human Peripheral Blood Monocytes Through a CD4-Independent Mechanism
Authors: Fantuzzi Laura , Canini Irene , Belardelli Filippo , Gessani Sandra
Published: April 2014

The present study was designed to evaluate the effect of the HIV-1 envelope glycoprotein gp120 on the expression of β-chemokines in cultured monocytes/macrophages. Treatment of either freshly isolated 1-day-cultured monocytes or 7-day-cultured monocyte-derived macrophages (MDM) with recombinant gp120-IIIB resulted in a specific and dose-dependent enhancement of secretion of monocyte chemoattractant protein-1, macrophage inflammatory protein-1β, and RANTES as well as a clear-cut increase in transcript accumulation. The expression of these mRNA was increased, but not superinduced, in the presence of cycloheximide. β-Chemokine secretion was also induced after exposure of monocyte cultures to gp120-JRFL and aldrithiol-2-inactivated R5 and X4 HIV-1 strains, retaining conformational and functional integrity of envelope proteins. In contrast, no β-chemokine secretion was triggered by X4 and R5 gp120 or aldrithiol-2-inactivated virus treatment of monocytoid cell lines that were fully responsive to LPS. The gp120-mediated effect was independent of its interaction with CD4, as preincubation with soluble CD4 did not abrogate β-chemokine induction. Moreover, triggering of CD4 receptor by a specific Ab did not result in any β-chemokine secretion. Interestingly, engagement of CCR5 and CXCR4 receptors by specific Abs as well as treatment with CCR5 and CXCR4 ligands induced β-chemokine secretion. On the whole, these results indicate that HIV-1 stimulates monocytes/macrophages to produce β-chemokines by a specific interaction of gp120 with HIV-1 coreceptors on the cell membrane. The expression of these related polypeptides may represent an important cellular response for regulating both the extent of viral infection and the recruitment of immune cells.
Ceramide Inhibits Lipopolysaccharide-Mediated Nitric Oxide Synthase and Cyclooxygenase-2 Induction in Macrophages: Effects on Protein Kinases and Transcription Factors
Authors: Hsu Ya-Wen , Chi Kwan-Hwa , Huang Wan-Chen , Lin Wan-Wan
Published: April 2014

The goal of this study was to elucidate whether triggering the sphingomyelin pathway modulates LPS-initiated responses. For this purpose we investigated the effects of N-acetylsphingosine (C2-ceramide) on LPS-induced production of NO and PGE2 in murine RAW 264.7 macrophages and explored the signaling pathways involved. We found that within a range of 10–50 μM, C2-ceramide inhibited LPS-elicited NO synthase and cyclooxygenase-2 induction accompanied by a reduction in NO and PGE2 formation. By contrast, a structural analog of C2-ceramide that does not elicit functional activity, C2-dihydroceramide, did not affect the LPS response. The nuclear translocation and DNA binding study revealed that ceramide can inhibit LPS-induced NF-κB and AP-1 activation. The immunocomplex kinase assay indicated that IκB kinase activity stimulated by LPS was inhibited by ceramide, which concomitantly reduced the IκBα degradation caused by LPS within 1–6 h. In concert with the decreased cytosolic p65 protein level, LPS treatment resulted in rapid nuclear accumulation of NF-κB subunit p65 and its association with the cAMP-responsive element binding protein. Ceramide coaddition inhibited all the LPS responses. In addition, LPS-induced PKC and p38 mitogen-activated protein kinase activation were overcome by ceramide. In conclusion, we suggest that ceramide inhibition of LPS-mediated induction of inducible NO synthase and cyclooxygenase-2 is due to reduction of the activation of NF-κB and AP-1, which might result from ceramide’s inhibition of LPS-stimulated IκB kinase, p38 mitogen-activated protein kinase, and protein kinase C.
Mechanism of Immune Dysfunction in Cancer Mediated by Immature Gr-1+ Myeloid Cells
Authors: Gabrilovich Dmitry I. , Velders Markwin P. , Sotomayor Eduardo M. , Kast W. Martin
Published: April 2014

The mechanism of tumor-associated T cell dysfunction remains an unresolved problem of tumor immunology. Development of T cell defects in tumor-bearing hosts are often associated with increased production of immature myeloid cells. In tumor-bearing mice, these immature myeloid cells are represented by a population of Gr-1+ cells. In this study we investigated an effect of these cells on T cell function. Gr-1+ cells were isolated from MethA sarcoma or C3 tumor-bearing mice using cell sorting. These Gr-1+ cells expressed myeloid cell marker CD11b and MHC class I molecules, but they lacked expression of MHC class II molecules. Tumor-induced Gr-1+ cells did not affect T cell responses to Con A and to a peptide presented by MHC class II. In sharp contrast, Gr-1+ cells completely blocked T cell response to a peptide presented by MHC class I in vitro and in vivo. Block of the specific MHC class I molecules on the surface of Gr-1+ cells completely abrogated the observed effects of these cells. Thus, immature myeloid cells specifically inhibited CD8-mediated Ag-specific T cell response, but not CD4-mediated T cell response. Differentiation of Gr-1+ cells in the presence of growth factors and all-trans retinoic acid completely eliminated inhibitory potential of these cells. This may suggest a new approach to cancer treatment.
The Involvement of TNF-α-Related Apoptosis-Inducing Ligand in the Enhanced Cytotoxicity of IFN-β-Stimulated Human Dendritic Cells to Tumor Cells
Authors: Liu Shuxun , Yu Yizhi , Zhang Minghui , Wang Wenya , Cao Xuetao
Published: April 2014

TNF-α-related apoptosis-inducing ligand (TRAIL) is characterized by its preferential induction of apoptosis of tumor cells but not normal cells. Dendritic cells (DCs), besides their role as APCs, now have been demonstrated to exert cytotoxicity or cytostasis on some tumor cells. Here, we report that both human CD34+ stem cell-derived DCs (CD34DCs) and human CD14+ monocyte-derived DCs (MoDCs) express TRAIL and exhibit cytotoxicity to some types of tumor cells partially through TRAIL. Moderate expression of TRAIL appeared on CD34DCs from the 8th day of culture and was also seen on freshly isolated monocytes. The level of TRAIL expression remained constant until DC maturation. TRAIL expression on immature CD34DCs or MoDCs was greatly up-regulated after IFN-β stimulation. Moreover, IFN-β could strikingly enhance the ability of CD34DCs or MoDCs to kill TRAIL-sensitive tumor cells, but LPS did not have such an effect. The up-regulation of TRAIL on IFN-β-stimulated DCs partially contributed to the increased cytotoxicity of DCs. Pretreatment of TRAIL-sensitive tumor cells with caspase-3 inhibitor could significantly increase their resistance to the cytotoxicity of IFN-β-stimulated DCs. In contrast, NF-κB inhibitor could significantly increase the sensitivity of tumor cells to the killing by nonstimulated or LPS-stimulated DCs. Our studies demonstrate that IFN-β-stimulated DCs are functionally cytotoxic. Thus, an innate mechanism of DC-mediated antitumor immunity might exist in vivo in which DCs act as effectors to directly kill tumor cells partially via TRAIL. Subsequently, DCs act as APCs involved in the uptake, processing, and presentation of apoptotic tumor Ags to cross-prime CD8+ CTL cells.
Modulation of CD8+ T Cell Response to Antigen by the Levels of Self MHC Class I
Authors: Santori Fabio R. , Arsov Ivica , Vukmanović Stanislav
Published: April 2014

The response of H-Y-specific TCR-transgenic CD8+ T cells to Ag is characterized by poor proliferation, cytolytic activity, and IFN-γ secretion. IFN-γ secretion, but not cytotoxic function, can be rescued by the B7.1 molecule, suggesting that costimulation can selectively enhance some, but not all, effector CD8+ T cell responses. Although the H-Y epitope binds H-2Db relatively less well than some other epitopes, it can induce potent CTL responses in nontransgenic mice, suggesting that the observed poor responsiveness of transgenic CD8+ T cells cannot be ascribed to the epitope itself. Previously reported reactivity of this TCR to H-2Ab is also not the cause of the poor responsiveness of the H-Y-specific CD8+ T cells, as H-Y-specific CD8+ T cells obtained from genetic backgrounds lacking H-2Ab also responded poorly. Rather, reducing the levels of H-2b class I molecules by breeding the mice to (C57BL/6 × B10.D2)F1 or TAP1+/− backgrounds partially restored cytotoxic activity and enhanced proliferative responses. These findings demonstrate that the self MHC class I gene dosage may regulate the extent of CD8+ T cell responsiveness to Ag.
META-Controlled env-Initiated Transcripts Encoding Superantigens of Murine Mtv29 and Mtv7 and Their Possible Role in B Cell Lymphomagenesis
Authors: Sen Namita , Simmons William J. , Thomas Rajan M. , Erianne Gregory , Zhang Da-Jun , Jaeggli Nelson S. , Huang Ching , Xiong Xiaozhong , Tsiagbe Vincent K. , Ponzio Nicholas M. , Thorbecke G. Jeanette
Published: April 2014

Spontaneous germinal center (GC)-derived B cell lymphomas of SJL mice (RCS) transcribe a 1.8-kb Mtv-29 mRNA under control of the META-env promoter. The encoded vSAg29 stimulates syngeneic Vβ16+ CD4+ T cells, thereby acquiring T cell help necessary for RCS growth. Other strains of B cell lymphoma-prone mice include Mtv29+ C57L and MA/MyJ, and the Mtv29− Mtv7+-recombinant inbred strain, SW × J-1. The lymphomas of these mice produce similar mouse mtv-vSAg-encoding mRNA, as characterized by Northern blotting, PCR, and RNase protection. A 1.8-kb mRNA in C57L/J and MA/MyJ lymphomas hybridized with an Mtv29-specific oligonucleotide, whereas SW × J-1 lymphomas produced 1.8-kb transcripts hybridizing with an Mtv7-specific oligonucleotide. Similar META-env-initiated transcripts were absent from LPS-activated B cells from any strain examined but were detected in Peyer’s patch RNA from SJL mice. Like typical SJL-derived RCS, all these lymphomas stimulated syngeneic CD4+ T cells and Vβ16+ T hybridoma cells. Immunohistochemical staining of primary tumors showed the presence of peanut agglutinin binding (PNA+) highly mitotic lymphoblasts, suggesting their GC derivation. The findings indicate that this novel mRNA for Mtv29 is present in B cell lymphomas from several Mtv29+ mouse strains. Additionally, this is the first description of the ability of Mtv7 to produce transcripts that are controlled and spliced identically to those of Mtv29 and that are expressed in SW × J-1, I-As+, lymphomas that also stimulate Vβ16+ T cells. Our results suggest an important role for mouse mtv-vSAgs and Vβ16 T cell stimulation in the development of GC-derived murine B cell lymphomas.
Antigen-Specific Primary Activation of CD8+ T Cells Within the Liver
Authors: Bertolino Patrick , Bowen David G. , McCaughan Geoffrey W. , Fazekas de St. Groth Barbara
Published: April 2014

It is generally accepted that naive T cells recirculate via the blood and lymph, but do not enter nonlymphoid tissues without prior activation and differentiation. In this study, we demonstrate that the liver is an exception to this rule. Naive Des-TCR transgenic CD8+ T cells specific for H-2Kb were selectively retained in the liver within a few minutes of adoptive transfer into transgenic Met-Kb mice expressing H-2Kb in the liver. Activated CD8+ cells were found in the liver, but not the blood, as soon as 2 h after transfer and underwent cell division and started to recirculate within 24 h of transfer. In contrast, CD8+ cells activated in the lymph nodes remained sequestered at that site for 2 days before entering the blood. Our results therefore suggest that, in addition to its previously described role as a non Ag-specific activated T cell graveyard, the liver is involved in Ag-specific activation of naive recirculating CD8+ T cells. This particular property of the liver, combined with the previously demonstrated ability of hepatocytes to induce tolerance by means of premature CD8+ T cell death, may be a major mechanism contributing to the acceptance of liver allografts and the chronicity of viral hepatitis.
The Mechanism of a Defective IFN-γ Response to Bacterial Toxins in an Atopic Dermatitis Model, NC/Nga Mice, and the Therapeutic Effect of IFN-γ, IL-12, or IL-18 on Dermatitis
Authors: Habu Yoshiko , Seki Shuhji , Takayama Eiji , Ohkawa Takashi , Koike Yuji , Ami Katsunori , Majima Takashi , Hiraide Hoshio
Published: April 2014

NC/Nga (NC) mice raised under conventional conditions (Conv. NC mice) spontaneously develop dermatitis similar to human atopic dermatitis, whereas NC mice raised under the specific pathogen-free conditions do not develop dermatitis. In the present study, we show that the representative Th1 cytokine, IFN-γ levels in the sera of NC mice, injected with either staphylococcal enterotoxin B or endotoxin (LPS), to be severalfold lower than those of normal mice. The low IFN-γ response to staphylococcal enterotoxin B was correlated to the lack of regular Vβ8+ T cells and Vβ8+ NK T cells, and the low IFN-γ response to LPS was correlated to an impaired IL-18 production of macrophages. The CD3-stimulated IL-4 production from liver and spleen T cells from Conv. NC mice in vitro was greatly augmented. The serum IL-4 levels of untreated Conv. NC mice also were higher than those of normal mice and specific pathogen-free NC mice. Treatment of Conv. NC mice either with IFN-γ, IL-12, or IL-18 twice a week from 4 wk of age substantially inhibited the elevation of the serum IgE levels, serum IL-4 levels, and dermatitis, and IL-12 or IL-18 treatment also reduced the in vitro IL-4 production from CD3-stimulated liver T cells. The systemic deficiency in the Th1 response to bacterial stimulation thus leads to a Th2-dominant state and may induce an abnormal cellular immune response in the skin accompanied with an overproduction of IgE and a susceptibility to dermatitis in NC mice.
Differential Production of IL-12, IFN-α, and IFN-γ by Mouse Dendritic Cell Subsets
Authors: Hochrein Hubertus , Shortman Ken , Vremec David , Scott Bernadette , Hertzog Paul , O’Keeffe Meredith
Published: April 2014

Dendritic cells (DC) not only stimulate T cells effectively but are also producers of cytokines that have important immune regulatory functions. In this study we have extended information on the functional differences between DC subpopulations to include differences in the production of the major immune-directing cytokines IL-12, IFN-α, and IFN-γ. Splenic CD4−8+ DC were identified as the major IL-12 producers in response to microbiological or T cell stimuli when compared with splenic CD4−8− or CD4+8− DC; however, all three subsets of DC showed similar IL-12 regulation and responded with increased IL-12 p70 production if IL-4 was present during stimulation. High level CD8 expression also correlated with extent of IL-12 production for DC isolated from thymus and lymph nodes. By using gene knockout mice we ruled out any role for CD8α itself, or of priming by T cells, on the superior IL-12-producing capacity of the CD8+ DC. Additionally, CD8+ DC were identified as the major producers of IFN-α compared with the two CD8− DC subsets, a finding that suggests similarity to the human plasmacytoid DC lineage. In contrast, the CD4−8− DC produced much more IFN-γ than the CD4−8+ or the CD4+8− DC under all conditions tested.
Distinct Autoreactive T Cell Responses to Native and Fragmented DNA Topoisomerase I: Influence of APC Type and IL-2
Authors: Oriss Timothy B. , Hu Paul Q. , Wright Timothy M.
Published: April 2014

Systemic sclerosis (SSc) is an autoimmune connective tissue disease of unknown etiology in which T cell responses to various autoantigens, including DNA topoisomerase I (Topo I), have been implicated. We investigated whether dendritic cells, generally considered to be the most potent APCs for the initiation of immune responses, would present either of two forms of Topo I to T cells more efficiently than PBMC APCs. Using cells from healthy controls and SSc patients, several important observations were made. First, neither APC type was able to initiate T cell proliferative responses to full-length native Topo I unless exogenous IL-2 was added. This is in contrast to vigorous T cell proliferation in response to Topo I polypeptide fragments presented by either APC type. Second, T cell responses to the full-length form of Topo I presented by dendritic cells were considerably lower than responses to Ag presented by PBMC APCs. Finally, no secondary T cell responses were observed unless the same Ag/APC combination as that used in the primary stimulation was maintained. These data indicate that different peptides are generated based upon the form of the Topo I and the APC that processes it. Taken together, these results suggest that a very specific combination of antigenic form and APC may be involved in breaking tolerance to Topo I in the early stages of development of SSc.
Fine Tuning of TCR Signaling by CD5
Authors: Azzam Hala S. , DeJarnette Jan B. , Huang Kun , Emmons Rebecca , Park Cheung-Seog , Sommers Connie L. , El-Khoury Dalal , Shores Elizabeth W. , Love Paul E.
Published: April 2014

Current data indicate that CD5 functions as an inhibitor of TCR signal transduction. Consistent with this role, thymocyte selection in TCR transgenic/CD5−/− mice is altered in a manner suggestive of enhanced TCR signaling. However, the impact of CD5 deletion on thymocyte selection varies depending on the transgenic TCR analyzed, ranging from a slight to a marked shift from positive toward negative selection. An explanation for the variable effect of CD5 on selection is suggested by the observation that CD5 surface expression is regulated by TCR signal intensity during development and CD5 surface levels on mature thymocytes and T cells parallel the avidity of the positively selecting TCR/MHC/ligand interaction. In this study, we generated mice that overexpress CD5 during thymocyte development (CD5-tg), and then examined the effect of CD5 overexpression or CD5 deletion (CD5−/−) on selection of thymocytes that express the same TCR transgenes. The results demonstrate that the effect on thymocyte selection of altering CD5 expression depends on the avidity of the selecting interaction and, consequently, the level of basal (endogenous) CD5 surface expression. Substitution of endogenous CD5 with a transgene encoding a truncated form of the protein failed to rescue the CD5−/− phenotype, demonstrating that the cytoplasmic domain of CD5 is required for its inhibitory function. Together, these results indicate that inducible regulation of CD5 surface expression during thymocyte selection functions to fine tune the TCR signaling response.
Prime-Boost Immunization with DNA Vaccine: Mucosal Route of Administration Changes the Rules
Authors: Eo Seong Kug , Gierynska Malgorzata , Kamar Amal Abou , Rouse Barry T.
Published: April 2014

In this study we assessed prime-boost immunization strategies with a DNA vaccine (gB DNA) and attenuated recombinant vaccinia virus vector (rvacgB), both encoding the gB protein of HSV, for their effectiveness at inducing mucosal as well as systemic immunity to HSV. Confirming the reports of others, systemic priming with gB DNA and systemic boosting with rvacgB were the most effective means of inducing serum Ab and splenic T cell responses. Nevertheless, the systemic prime-boost approach failed to induce detectable humoral or T cell responses at mucosal sites. However, such responses, at both proximal and distal locations, were induced if immunizations, especially the priming dose, were administered mucosally. Curiously, whereas optimal immunity with systemic priming and boosting occurred when gB DNA was used to prime and rvacgB was used as a boost, mucosal responses were optimal when animals were mucosally primed with rvacgB and boosted with gB DNA given mucosally. Furthermore, notable mucosal responses also occurred in animals mucosally primed with rvacgB and subsequently boosted systemically with gB DNA. Because the mucosal prime-boost immunization protocol also induced excellent systemic immune responses, the approach should be useful to vaccinate against agents for which both mucosal and systemic immunity are important for protection.
CD150 Association with Either the SH2-Containing Inositol Phosphatase or the SH2-Containing Protein Tyrosine Phosphatase Is Regulated by the Adaptor Protein SH2D1A
Authors: Shlapatska Larysa M. , Mikhalap Svitlana V. , Berdova Anna G. , Zelensky Oleksander M. , Yun Theodore J. , Nichols Kim E. , Clark Edward A. , Sidorenko Svetlana P.
Published: April 2014

CD150 (SLAM/IPO-3) is a cell surface receptor that, like the B cell receptor, CD40, and CD95, can transmit positive or negative signals. CD150 can associate with the SH2-containing inositol phosphatase (SHIP), the SH2-containing protein tyrosine phosphatase (SHP-2), and the adaptor protein SH2 domain protein 1A (SH2D1A/DSHP/SAP, also called Duncan’s disease SH2-protein (DSHP) or SLAM-associated protein (SAP)). Mutations in SH2D1A are found in X-linked lymphoproliferative syndrome and non-Hodgkin’s lymphomas. Here we report that SH2D1A is expressed in tonsillar B cells and in some B lymphoblastoid cell lines, where CD150 coprecipitates with SH2D1A and SHIP. However, in SH2D1A-negative B cell lines, including B cell lines from X-linked lymphoproliferative syndrome patients, CD150 associates only with SHP-2. SH2D1A protein levels are up-regulated by CD40 cross-linking and down-regulated by B cell receptor ligation. Using GST-fusion proteins with single replacements of tyrosine at Y269F, Y281F, Y307F, or Y327F in the CD150 cytoplasmic tail, we found that the same phosphorylated Y281 and Y327 are essential for both SHP-2 and SHIP binding. The presence of SH2D1A facilitates binding of SHIP to CD150. Apparently, SH2D1A may function as a regulator of alternative interactions of CD150 with SHP-2 or SHIP via a novel TxYxxV/I motif (immunoreceptor tyrosine-based switch motif (ITSM)). Multiple sequence alignments revealed the presence of this TxYxxV/I motif not only in CD2 subfamily members but also in the cytoplasmic domains of the members of the SHP-2 substrate 1, sialic acid-binding Ig-like lectin, carcinoembryonic Ag, and leukocyte-inhibitory receptor families.
Quantitation of Lysozyme Peptides Bound to Class II MHC Molecules Indicates Very Large Differences in Levels of Presentation
Authors: Velazquez Carlos , DiPaolo Richard , Unanue Emil R.
Published: April 2014

Knowing the abundance of peptides presented by MHC molecules is a crucial aspect for understanding T cell activation and tolerance. In this report we determined the relative abundance of four distinct peptide families after the processing of the model Ag hen egg-white lysozyme. The development of a sensitive immunochemical approach reported here made it possible to directly quantitate the abundance of these four epitopes presented by APCs, both in vitro and in vivo. We observed a wide range of presentation among these four different epitopes presented on the surface of APCs, with 250-fold differences or more between the most abundant epitope (48–63) and the least abundant epitopes. Importantly, we observe similar ratios of presentation from APCs in vitro as well as from APCs from the spleens and thymi of hen egg-white lysozyme transgenic mice. We discuss the relationship between the amount of peptide presented and their binding to I-Ak molecules, immunogenicity, and tolerogenicity.
Prolonged Exposure of T Cells to TNF Down-Regulates TCRζ and Expression of the TCR/CD3 Complex at the Cell Surface
Authors: Isomäki Pia , Panesar Manvinder , Annenkov Alex , Clark Joanna M. , Foxwell Brian M. J. , Chernajovsky Yuti , Cope Andrew P.
Published: April 2014

A role for TNF-α in the pathogenesis of chronic inflammatory disease is now firmly established. Paradoxically, TNF also has potent immunomodulatory effects on CD4+ T lymphocytes, because Ag-specific proliferative and cytokine responses are suppressed following prolonged exposure to TNF. We explored whether TNF attenuated T cell activation by uncoupling proximal TCR signal transduction pathways using a mouse T cell hybridoma model. Chronic TNF exposure induced profound, but reversible, T cell hyporesponsiveness, with TNF-treated T cells requiring TCR engagement with higher peptide concentrations for longer periods of time for commitment to IL-2 production. Subsequent experiments revealed that chronic TNF exposure led to a reversible loss of TCRζ chain expression, in part through a reduction in gene transcription. Down-regulation of TCRζ expression impaired TCR/CD3 assembly and expression at the cell surface and uncoupled membrane-proximal tyrosine phosphorylation events, including phosphorylation of the TCRζ chain itself, CD3ε, ZAP-70 protein tyrosine kinase, and linker for activation of T cells (LAT). Intracellular Ca2+ mobilization was also suppressed in TNF-treated T cells. We propose that TNF may contribute to T cell hyporesponsiveness in chronic inflammatory and infectious diseases by mechanisms that include down-regulation of TCRζ expression. We speculate that by uncoupling proximal TCR signals TNF could also interrupt mechanisms of peripheral tolerance that are dependent upon intact TCR signal transduction pathways.
Essential Requirement of Antigen Presentation by Monocyte Lineage Cells for the Activation of Primary Human γδ T Cells by Aminobisphosphonate Antigen
Authors: Miyagawa Fumi , Tanaka Yoshimasa , Yamashita Seiji , Minato Nagahiro
Published: April 2014

Human γδ T cells respond to nonpeptide Ags such as pyrophosphomonoesters and alkylamines in a γδ TCR-dependent manner in the absence of other APCs. Recently, aminobisphosphonates such as pamidronate have also been shown to activate human γδ T cells. In the present study, we indicate that activation of primary γδ T cells by pamidronate strictly depends on the presence of monocyte-lineage cells, unlike that by pyrophosphomonoesters. Thus, although pamidronate induced cell clustering, proliferation, and IFN-γ production of γδ T cells in the culture of PBMC, it failed to induce any of these activities in the culture of purified primary γδ T cells. By adding back the purified monocytes, however, both cell clustering and IFN-γ production of γδ T cells by pamidronate could be restored. The pamidronate-pulsed, but not untreated, myelomonocytic line, THP-1, was capable of activating the purified γδ T cells to produce IFN-γ, which was associated with the down-regulation of γδ TCR. Furthermore, pamidronate-pulsed THP-1 cells were significantly more susceptible to γδ T cell-mediated cytotoxicity than untreated THP-1. Also, TCR-defective Jurkat T cells transfected with γδ TCR genes produced a significant level of IL-2 in response to the pamidronate-pulsed THP-1 cells. These results have suggested strongly that human γδ T cells are functionally activated via γδ TCR by aminobisphosphonate Ag presented on the surface of monocyte lineage cells rather than directly by its free form .
IL-12 Enhances CD8 T Cell Homeostatic Expansion
Authors: Kieper William C. , Prlic Martin , Schmidt Clint S. , Mescher Matthew F. , Jameson Stephen C.
Published: April 2014

The size of the T lymphocyte pool is maintained by regulation of T cell production, proliferation, and survival. Under the pressure of a T lymphopenic environment, mature naive T cells begin to proliferate in the absence of Ag, a process called homeostatic expansion. Homeostatic expansion involves TCR recognition of self peptide/MHC ligands, but less is known about the soluble factors that regulate this process. Here we show that IL-12 dramatically enhanced the homeostatic proliferation of CD8 T cells. In contrast, IL-2 had no beneficial effect on homeostatic expansion and, in fact, inhibited T cell expansion induced by IL-12. Using gene-targeted mice, we showed that IL-12 acted directly on the T cells to enhance homeostatic expansion, but that IL-12 cannot override the requirement for TCR interaction with self peptide/MHC ligands in homeostatic expansion. These data indicate that inflammatory cytokines may modulate T cell homeostasis after lymphopenia and have implications for regulation of the T cell repertoire and autoimmunity.
Lymphocyte Lineages at Mucosal Effector Sites: Rat Salivary Glands
Authors: O’Sullivan Nancy L. , Skandera Cheryl A. , Montgomery Paul C.
Published: April 2014

Development of T cell lineages and the role of the thymus as a source of immature T cells in parotid (PG) and submandibular salivary glands (SMG) were studied in Fischer 344 rats using the Thy-1/CD45RC/RT6 expression model. In addition, the phenotypes of salivary gland lymphocytes were compared with other conventional and extrathymic populations. PG mononuclear cells consisted of T cells (38%), B cells (29%), and NK cells (4%). SMG had 19% T cells, 7% B cells, 37% NK cells, and an unusual population of CD3−/RT6+ cells. In comparison with lymph node (LN), both PG and SMG were enriched in immature (Thy-1+) and activated (Thy-1−/CD45RC−/RT6−) T cells. Unchanged percentages of Thy-1+ T cells in PG and SMG following short-term adult thymectomy indicated that immature salivary gland T cells had an extrathymic source. In contrast, thymectomy eliminated LN recent thymic emigrants. SMG had T cells with characteristics of extrathymic populations, expressing TCRγδ+ (28%), the CD8αα homodimer (11%), and NKR-P1A (66%). Many SMG T cells expressed integrin αEβ7. PG T cells resembled those isolated from LN in respect to TCR and CD8 isoform usage, but were enriched in αEβ7+ T cells and in NKT cells. Thus, salivary gland mononuclear cells are composed of a variety of subpopulations whose distributions differ between SMG and PG and are distinct from LN. These studies provide a basis for further investigation of regionalization in the mucosal immune network and are relevant to the design of vaccine regimens and intervention during pathological immune processes.
IFN-α and IL-10 Induce the Differentiation of Human Type 1 T Regulatory Cells
Authors: Levings Megan K. , Sangregorio Romina , Galbiati Francesca , Squadrone Stefania , de Waal Malefyt Rene , Roncarolo Maria-Grazia
Published: April 2014

CD4+ T regulatory type 1 (Tr1) cells suppress Ag-specific immune responses in vitro and in vivo. Although IL-10 is critical for the differentiation of Tr1 cells, the effects of other cytokines on differentiation of naive T cells into Tr1 cells have not been investigated. Here we demonstrate that endogenous or exogenous IL-10 in combination with IFN-α, but not TGF-β, induces naive CD4+ T cells derived from cord blood to differentiate into Tr1 cells: IL-10+IFN-γ+IL-2−/lowIL-4−. Naive CD4+ T cells derived from peripheral blood require both exogenous IL-10 and IFN-α for Tr1 cell differentiation. The proliferative responses of the Tr1-containing lymphocyte populations, following activation with anti-CD3 and anti-CD28 mAbs, were reduced. Similarly, cultures containing Tr1 cells displayed reduced responses to alloantigens via a mechanism that was partially mediated by IL-10 and TGF-β. More importantly, Tr1-containing populations strongly suppressed responses of naive T cells to alloantigens. Collectively, these results show that IFN-α strongly enhances IL-10-induced differentiation of functional Tr1 cells, which represents a first major step in establishing specific culture conditions to generate T regulatory cells for biological and biochemical analysis, and for cellular therapy to induce peripheral tolerance in humans.
Differential Roles of Lck and Itk in T Cell Response to Antigen Recognition Revealed by Calcium Imaging and Electron Microscopy
Authors: Donnadieu Emmanuel , Lang Valérie , Bismuth Georges , Ellmeier Wilfried , Acuto Oreste , Michel Frédérique , Trautmann Alain
Published: April 2014

Ag recognition triggered at the interface between a T cell and an APC is conditioned by cell-cell adhesion and cytoskeletal remodeling. The role played in these phenomena by Lck and Itk, two protein tyrosine kinases essential for T cell signaling, was examined. Early T cell responses (membrane ruffling, Ca2+ response, APC-T cell adhesion) were monitored in T cells overexpressing kinase-defective (KD) Lck and Itk mutants by combining fluorescence imaging and electron microscopy. Neither Lck nor Itk appears to be involved in the Ag-independent formation of a small and labile contact interface between T cells and APCs. By contrast, the Ag-induced Ca2+ response in a cell population is similarly blunted in both KD transfectants. However, the underlying mechanisms are strikingly different for the two kinases. The major effect of Lck-KD is to reduce the probability of giving rise to quasi-normal Ca2+ responses, whereas overexpression of Itk-KD results in a tuning down of all single-cell Ca2+ responses. In addition, Lck, but not Itk, is required for the formation of a stable T/APC conjugate and for T cell polarization after Ag stimulation. Overall, our results lead to a clear distinction between Lck and Itk. Lck plays an ignition role, controlling all the downstream events tested here, whereas Itk amplifies the Ca2+ response, but is dispensable for APC-induced adhesive and morphological responses.
The Vasodilator-Stimulated Phosphoprotein Is Regulated by Cyclic GMP-Dependent Protein Kinase During Neutrophil Spreading
Authors: Lawrence Donald W. , Pryzwansky Katherine B.
Published: April 2014

The expression and phosphorylation state of the vasodilator-stimulated phosphoprotein (VASP), a membrane-associated focal adhesion protein, was investigated in human neutrophils. Adhesion and spreading of neutrophils induced the rapid phosphorylation of VASP. The phosphorylation of VASP was dependent on cell spreading, as VASP was expressed as a dephosphorylated protein in round adherent cells and was phosphorylated at the onset of changes in cell shape from round to spread cells. Immunofluorescence microscopy demonstrated that VASP was localized at the cell cortex in round cells and redistributed to focal adhesions at the ventral surface of the cell body during cell spreading. Dual labeling of spread cells indicated that VASP was colocalized with F-actin in filopodia and in focal adhesions, suggesting that the phosphorylation of VASP during cell spreading may be involved in focal adhesion complex organization and actin dynamics. VASP is a prominent substrate for both cGMP-dependent protein kinase (cGK) and cAMP-dependent protein kinase. Evidence suggested that cGK regulated neutrophil spreading, as both VASP phosphorylation and neutrophil spreading were inhibited by Rp-8-pCPT-cGMPS (cGK inhibitor), but not KT5720 (cAMP-dependent protein kinase inhibitor). In contrast, neutrophil spreading was accelerated when cGMP levels were elevated with 8-Br-cGMP, a direct activator of cGK. Furthermore, the same conditions that lead to VASP phosphorylation during neutrophil adherence and spreading induced significant elevations of cGMP in neutrophils. These results indicate that cGMP/cGK signal transduction is required for neutrophil spreading, and that VASP is a target for cGK regulation.
Tumor Progression Despite Efficient Tumor Antigen Cross-Presentation and Effective “Arming” of Tumor Antigen-Specific CTL
Authors: Nelson Delia J. , Mukherjee Sutapa , Bundell Christine , Fisher Scott , van Hagen Deborah , Robinson Bruce
Published: April 2014

To determine whether APC function or “arming” of CTL for lytic function are the points at which Ags from a nonimmunogenic tumor fail to induce an effective immune response, we established a murine tumor model that expressed intracellular OVA and selected a clone (cOVA-9) that remained susceptible to lysis by specific CD8+ T cells throughout tumor growth. Viable cOVA-9 tumor cells grew in normal mice at a rate similar to the parental tumor, and vaccination with irradiated cOVA-9 cells did not induce protection against itself or the parental line, confirming its nonimmunogenic status. In vivo evaluation during tumor growth demonstrated persisting tumor Ag cross-presentation accompanied by the generation of potent, specific CTL which were detectable when tumors were barely palpable. Despite the presence of highly active CTL in the tumor-draining lymph nodes, there was no apparent lysis of tumor-associated APC. These data show that tumor-draining APC are not dysfunctional with regard to two crucial processes, in vivo tumor Ag cross-presentation and specific CTL arming, and that failure to prevent tumor growth is not in the induction phase, but in the effector phase and occurs within the tumor itself before the tumor matrix is established.
CD24 Induces Apoptosis in Human B Cells Via the Glycolipid-Enriched Membrane Domains/Rafts-Mediated Signaling System
Authors: Suzuki Toyo , Kiyokawa Nobutaka , Taguchi Tomoko , Sekino Takaomi , Katagiri Yohko U. , Fujimoto Junichiro
Published: April 2014

The glycosylphosphatidylinositol-anchored CD24 protein is a B cell differentiation Ag that is expressed on mature resting B cells but disappears upon Ag stimulation. We used Burkitt’s lymphoma (BL) cells, which are thought to be related to germinal center B cells, to examine the biological effect of Ab-mediated CD24 cross-linking on human B cells and observed 1) induction of apoptosis in BL cells mediated by cross-linking of CD24; and 2) synergism between the cross-linking of CD24 and that of the B cell receptor for Ag in the effect on apoptosis induction. We also observed activation of mitogen-activated protein kinases following CD24 cross-linking, suggesting that CD24 mediates the intracellular signaling that leads to apoptosis in BL cells. Although CD24 has no cytoplasmic portion to transduce signals intracellularly, analysis of biochemically separated glycolipid-enriched membrane (GEM) fractions indicated enhanced association of CD24 and Lyn protein tyrosine kinase in GEM as well as increased Lyn kinase activity after CD24 cross-linking, suggesting that CD24 mediates intracellular signaling via a GEM-dependent mechanism. Specific microscopic cocapping of CD24 and Lyn, but not of other kinases, following CD24 cross-linking supported this idea. We further observed that apoptosis induction by cross-linking is a common feature shared by GEM-associated molecules expressed on BL cells, including GPI-anchored proteins and glycosphingolipids. CD24-mediated apoptosis in BL cells may provide a model for the cell death mechanism initiated by GEM-associated molecules, which is closely related to B cell receptor for Ag-mediated apoptosis.