bluuebunny/crossref_metadata_2025 huggingface dataset:
Deficiency of the Src Homology Region 2 Domain-Containing Phosphatase 1 (SHP-1) Causes Enrichment of CD4+CD25+ Regulatory T Cells
Authors: Carter Jennifer D. , Calabrese Gina M. , Naganuma Makoto , Lorenz Ulrike
Published: April 2014

A subpopulation of T cells, named regulatory T cells (Treg cells), has been shown to play a key role in tolerance and the prevention of autoimmunity. It is not known how changes in TCR signal strength during thymic T cell development affect the generation of a Treg population. In this study, we took two different strategies to modulate the TCR signal strength: an intrinsic approach, where signaling was enhanced by the loss of a negative regulator, and an extrinsic approach, where signaling strength was altered through variations in the concentrations of the selecting peptide. The tyrosine phosphatase Src homology region 2 domain-containing phosphatase 1 (SHP-1) is a known negative regulator of TCR-mediated signaling. motheaten mice, lacking expression of SHP-1, showed a 2- to 3-fold increase in the percentage of CD4+CD25+ Treg cells within the CD4+ T cells. Similarly, the percentage of Treg cells was heightened in fetal thymic organ cultures (FTOCs) derived from motheaten mice compared with wild-type FTOCs, thus establishing the thymic origin of these Treg cells. Using FTOCs derived from DO11.10 TCR transgenic mice, we demonstrated that exposure to increasing concentrations of the cognate OVA peptide favored the appearance of Treg cells. Our data suggest that the development of CD4+CD25+ Treg cells is intrinsically different from non-Treg cells and that Treg cells are selectively enriched under conditions of enhanced negative selection. Our data also reveal a key role for the SHP-1-mediated regulation of TCR signal strength in influencing the ratio of Treg vs non-Treg cells.
Role of TLR in B Cell Development: Signaling through TLR4 Promotes B Cell Maturation and Is Inhibited by TLR2
Authors: Hayashi Elize A. , Akira Shizuo , Nobrega Alberto
Published: April 2014

The role of TLR4 in mature B cell activation is well characterized. However, little is known about TLR4 role in B cell development. Here, we analyzed the effects of TLR4 and TLR2 agonists on B cell development using an in vitro model of B cell maturation. Highly purified B220+IgM− B cell precursors from normal C57BL/6 mouse were cultured for 72 h, and B cell maturation in the presence of the TLR agonists was evaluated by expression of IgM, IgD, CD23, and AA4. The addition of LPS or lipid A resulted in a marked increase in the percentage of CD23+ B cells, while Pam3Cys had no effect alone, but inhibited the increase of CD23+ B cell population induced by lipid A or LPS. The TLR4-induced expression of CD23 is not accompanied by full activation of the lymphocyte, as suggested by the absence of activation Ag CD69. Experiments with TLR2-knockout mice confirmed that the inhibitory effects of Pam3Cys depend on the expression of TLR2. We studied the effects of TLR-agonists on early steps of B cell differentiation by analyzing IL-7 responsiveness and phenotype of early B cell precursors: we found that both lipid A and Pam3Cys impaired IL-7-dependent proliferation; however, while lipid A up-regulates B220 surface marker, consistent with a more mature phenotype of the IgM− precursors, Pam3Cys keeps the precursors on a more immature stage. Taken together, our results suggest that TLR4 signaling favors B lymphocyte maturation, whereas TLR2 arrests/retards that process, ascribing new roles for TLRs in B cell physiology.
Analysis of the Role of Negative T Cell Costimulatory Pathways in CD4 and CD8 T Cell-Mediated Alloimmune Responses In Vivo
Authors: Ito Toshiro , Ueno Takuya , Clarkson Michael R. , Yuan Xueli , Jurewicz Mollie M. , Yagita Hideo , Azuma Miyuki , Sharpe Arlene H. , Auchincloss Hugh , Sayegh Mohamed H. , Najafian Nader
Published: April 2014

Negative costimulatory signals mediated via cell surface molecules such as CTLA-4 and programmed death 1 (PD-1) play a critical role in down-modulating immune responses and maintaining peripheral tolerance. However, their role in alloimmune responses remains unclear. This study examined the role of these inhibitory pathways in regulating CD28-dependent and CD28-independent CD4 and CD8 alloreactive T cells in vivo. CTLA-4 blockade accelerated graft rejection in C57BL/6 wild-type recipients and in a proportion of CD4−/− but not CD8−/− recipients of BALB/c hearts. The same treatment led to prompt rejection in CD28−/− and a smaller proportion of CD4−/−CD28−/− mice with no effect in CD8−/−CD28−/− recipients. These results indicate that the CTLA-4:B7 pathway provides a negative signal to alloreactive CD8+ T cells, particularly in the presence of CD28 costimulation. In contrast, PD-1 blockade led to accelerated rejection of heart allografts only in CD28−/− and CD8−/−CD28−/− recipients. Interestingly, PD-1 ligand (PD-L1) blockade led to accelerated rejection in wild-type mice and in all recipients lacking CD28 costimulation. This effect was accompanied by expansion of IFN-γ-producing alloreactive T cells and enhanced generation of effector T cells in rejecting allograft recipients. Thus, the PD-1:PD-L1 pathway down-regulates alloreactive CD4 T cells, particularly in the absence of CD28 costimulation. The differential effects of PD-1 vs PD-L1 blockade support the possible existence of a new receptor other than PD-1 for negative signaling through PD-L1. Furthermore, PD-1:PD-L1 pathway can regulate alloimmune responses independent of an intact CD28/CTLA-4:B7 pathway. Harnessing physiological mechanisms that regulate alloimmunity should lead to development of novel strategies to induce durable and reproducible transplantation tolerance.
Development of Murine Plasmacytoid Dendritic Cells Defined by Increased Expression of an Inhibitory NK Receptor, Ly49Q
Authors: Omatsu Yoshiki , Iyoda Tomonori , Kimura Yukino , Maki Akiko , Ishimori Masaki , Toyama-Sorimachi Noriko , Inaba Kayo
Published: April 2014

Plasmacytoid dendritic cells (PDCs) are defined in mice by a unique combination of markers: CD11c, B220, and Ly6C/G. We have reported previously that PDCs express Ly49Q, a lectin-type killer cell inhibitory receptor. We now find that different expression levels of Ly49Q define sequential developmental stages of PDCs in bone marrow. Although PDCs in spleen and lymph nodes express high levels of Ly49Q, a significant portion of CD11c+B220+ PDCs in bone marrow lack Ly49Q, as well as the CD4 and MHC II. Purified Ly49Q− marrow PDCs spontaneously up-regulate Ly49Q after overnight culture without cell proliferation and acquire most features of typical PDCs in spleen. When exposed to TLR ligands, such as CpG-oligodeoxynucleotide and hemagglutinating virus of Japan (Sendai virus), Ly49Q− PDCs increase CD86 and MHC class II expression but produce less IFN-αβ, IL-6, and IL-12p70 than Ly49Q+ PDCs, although they are able to produce comparable amounts of TNF-α. However, interestingly, Ly49Q− PDCs do not produce TNF-α in response to the TLR2 ligand, Pam3SCK4, whereas Ly49Q+ PDCs did. Therefore, Ly49Q is a new marker to identify a precursor form of PDCs that participates in innate immunity.
Alternative Splicing Generates Putative Soluble CD83 Proteins That Inhibit T Cell Proliferation
Authors: Dudziak Diana , Nimmerjahn Falk , Bornkamm Georg W. , Laux Gerhard
Published: April 2014

CD83 is expressed on mature dendritic cells and activated lymphocytes and has been implicated to play an important role during T cell development in the thymus. In contrast, not much is known about the function of CD83 in the periphery. Soluble forms of CD83 have been detected in the serum, but neither the function nor the mechanism of how these soluble forms of CD83 are generated are fully understood. In this study, we report the identification of four different transcripts of CD83 in unstimulated PBMCs. Sequence analysis demonstrated that the longest form codes for transmembrane CD83 (CD83-TM), whereas the smaller transcripts are splice variants of full-length CD83, coding for putative soluble CD83 proteins. Stimulation of PBMCs with PHA, TNF-α, or LPS leads to the up-regulation of the full-length CD83 transcript and to a strong down-regulation of two of the three smaller transcripts. The smallest CD83 splice product can be translated efficiently into protein, and recombinant soluble CD83 shows a strong inhibitory effect on T cell proliferation in MLRs. Our results suggest that the constitutive production of soluble forms of CD83 under steady-state conditions may have an important function in regulating immune homeostasis.
OX40 Ligand and CD30 Ligand Are Expressed on Adult but Not Neonatal CD4+CD3− Inducer Cells: Evidence That IL-7 Signals Regulate CD30 Ligand but Not OX40 Ligand Expression
Authors: Kim Mi-Yeon , Anderson Graham , White Andrea , Jenkinson Eric , Arlt Wiebke , Martensson Inga-Lill , Erlandsson Lena , Lane Peter J. L.
Published: April 2014

In this report, we have examined the expression of the T cell survival signals, OX40 ligand (OX40L) and CD30 ligand (CD30L) on CD4+CD3−CD11c−B220−IL-7Rα+ inducer cells from birth to adulthood in mice. We found that adult but not neonatal inducer cells expressed high levels of OX40L and CD30L, whereas their expression of TNF-related activation-induced cytokine (TRANCE) and receptor activator of NF-κB (RANK) was comparable. The failure of neonatal inducer cells to express the ligands that rescue T cells helps to explain why exposure to Ag in neonatal life induces tolerance rather than immunity. The expression of OX40L and CD30L on inducer cells increased gradually in the first few weeks of life achieving essentially normal levels around the time mice were weaned. We found that IL-7 signaling through the common cytokine receptor γ-chain was critical for the optimal expression of both TNF-related activation-induced cytokine and CD30L but not OX40L. Furthermore, glucocorticoids, which potently suppress T effector function, did not influence the expression of OX40L and CD30L in the presence of IL-7.
Carcinoembryonic Antigen (CEA) Inhibits NK Killing via Interaction with CEA-Related Cell Adhesion Molecule 1
Authors: Stern Noam , Markel Gal , Arnon Tal I. , Gruda Raizy , Wong Henry , Gray-Owen Scott D. , Mandelboim Ofer
Published: April 2014

The NK killing activity is regulated by activating and inhibitory NK receptors. All of the activating ligands identified so far are either viral or stress-induced proteins. The class I MHC proteins are the ligands for most of the inhibitory NK receptors. However, in the past few years, several receptors have been identified that are able to inhibit NK killing independently of class I MHC recognition. We have previously demonstrated the existence of a novel inhibitory mechanism of NK cell cytotoxicity mediated by the homophilic carcinoembryonic Ag (CEA)-related cell adhesion molecule 1 (CEACAM1) interactions. In this study, we demonstrate that CEACAM1 also interacts heterophilically with the CEA protein. Importantly, we show that these heterophilic interactions of CEA and CEACAM1 inhibit the killing by NK cells. Because CEA is expressed on a wide range of carcinomas and commonly used as tumor marker, these results represent a novel role for the CEA protein enabling the escape of tumor cells from NK-mediated killing. We further characterize, for the first time, the CEACAM1-CEA interactions. Using functional and binding assays, we demonstrate that the N domains of CEACAM1 and CEA are crucial but not sufficient for both the CEACAM1-CEACAM1 homophilic and CEACAM1-CEA heterophilic interactions. Finally, we suggest that the involvement of additional domains beside the N domain in the heterophilic and homophilic interactions is important for regulating the balance between cis and trans interactions.
Rapid and Long-Term Disappearance of CD4+ T Lymphocyte Responses Specific for Anaplasma Marginale Major Surface Protein-2 (MSP2) in MSP2 Vaccinates following Challenge with Live A. marginale
Authors: Abbott Jeffrey R. , Palmer Guy H. , Kegerreis Kimberly A. , Hetrick Peter F. , Howard Chris J. , Hope Jayne C. , Brown Wendy C.
Published: April 2014

In humans and ruminants infected with Anaplasma, the major surface protein 2 (MSP2) is immunodominant. Numerous CD4+ T cell epitopes in the hypervariable and conserved regions of MSP2 contribute to this immunodominance. Antigenic variation in MSP2 occurs throughout acute and persistent infection, and sequentially emerging variants are thought to be controlled by variant-specific Ab. This study tested the hypothesis that challenge of cattle with Anaplasma marginale expressing MSP2 variants to which the animals had been immunized, would stimulate variant epitope-specific recall CD4+ T cell and IgG responses and organism clearance. MSP2-specific T lymphocyte responses, determined by IFN-γ ELISPOT and proliferation assays, were strong before and for 3 wk postchallenge. Surprisingly, these responses became undetectable by the peak of rickettsemia, composed predominantly of organisms expressing the same MSP2 variants used for immunization. Immune responsiveness remained insignificant during subsequent persistent A. marginale infection up to 1 year. The suppressed response was specific for A. marginale, as responses to Clostridium vaccine Ag were consistently observed. CD4+CD25+ T cells and cytokines IL-10 and TGF-β1 did not increase after challenge. Furthermore, a suppressive effect of nonresponding cells was not observed. Lymphocyte proliferation and viability were lost in vitro in the presence of physiologically relevant numbers of A. marginale organisms. These results suggest that loss of memory T cell responses following A. marginale infection is due to a mechanism other than induction of T regulatory cells, such as peripheral deletion of MSP2-specific T cells.
Selective Expression of the Cre Recombinase in Late-Stage Thymocytes Using the Distal Promoter of the Lck Gene
Authors: Zhang Dong Ji , Wang Qi , Wei Jie , Baimukanova Gyulnar , Buchholz Frank , Stewart A. Francis , Mao Xiaohong , Killeen Nigel
Published: April 2014

Transgenic mouse lines were generated that express the Cre recombinase under the control of the distal promoter of the mouse Lck gene. Cre recombination in four of these lines of transgenic mice was characterized at the single cell level using ROSA26-regulated loxP-Stop-loxP-βgeo and loxP-Stop-loxP-YFP reporter mouse lines. Two of the lines showed T cell-restricted Cre recombination, whereas the other two also expressed Cre in B cells, NK cells, and monocytes. Cre recombination began at a late stage of T cell development (at or after up-regulation of the TCR during positive selection) in the two T cell-restricted lines. Lines of mice that express the Cre recombinase at late stages of thymocyte development are of value for determining the impact of mutations on T cell function in the absence of complicating effects on early thymocyte selection.
Impairment of Thymocyte Development by Dominant-Negative Kuzbanian (ADAM-10) Is Rescued by the Notch Ligand, Delta-1
Authors: Manilay Jennifer O. , Anderson Ana C. , Kang Chulho , Robey Ellen A.
Published: April 2014

Although Notch plays a crucial role in T cell development, regulation of Notch signaling in the thymus is not well understood. Kuzbanian, an ADAM protease, has been implicated in the cleavage of both Notch receptors and the Notch ligand, Delta. In this study we show that the expression of a dominant-negative form of Kuzbanian (dnKuz) leads to reduced TCRβ expression in double-negative thymocytes and to a partial block between the double-negative to double-positive stages of development. These defects were rescued by overexpression of Delta-1 on thymocytes. Mixed chimeras showed a cell-autonomous block by dnKuz, but non-cell-autonomous rescue by Delta-1. This suggests that dnKuz impairs Notch signaling in receiving cells, and increasing Delta-1 on sending cells overcomes this defect. Interestingly, the expression of an activated form of Notch-1 rescued some, but not all, the defects in dnKuz Tg mice. Our data suggest that multiple Notch-dependent steps in early thymocyte development require Kuzbanian, but differ in the involvement of other Notch signaling components.
Enhanced CD4 T Cell Responsiveness in the Absence of 4-1BB
Authors: Lee Seung-Woo , Vella Anthony T. , Kwon Byoung S. , Croft Michael
Published: April 2014

The 4-1BB (CD137) is a member of the TNFR superfamily, and is expressed on several cell types, including activated T cells. Although 4-1BB ligation by agonistic Ab or 4-1BB ligand-expressing APCs can costimulate T cells, the physiological significance of 4-1BB expression in vivo during T cell responses is still being elucidated. In this study, we have addressed the impact on CD4 T cell priming when 4-1BB is absent after gene targeting. Surprisingly, 4-1BB−/− mice generated more enhanced effector CD4 T cell responses to OVA protein in adjuvant, even though Ab responses in 4-1BB−/− mice were normal. Using an adoptive transfer system with OT-II TCR transgenic CD4 T cells, we found that 4-1BB−/− CD4 cells responding in a 4-1BB-sufficient environment had enhanced cell division compared with wild-type cells and displayed augmented clonal expansion during the primary response. This was not due to a developmental defect as 4-1BB-deficient CD4 cells could respond normally to Ag in vitro. These results demonstrate that the absence of 4-1BB can make CD4 T cells hyperresponsive to protein Ag in vivo, suggesting a new unappreciated negative regulatory role of 4-1BB when expressed on a T cell.
Leptin Promotes Differentiation and Survival of Human Dendritic Cells and Licenses Them for Th1 Priming
Authors: Mattioli Benedetta , Straface Elisabetta , Quaranta Maria Giovanna , Giordani Luciana , Viora Marina
Published: April 2014

Leptin is an adipocyte-derived hormone/cytokine that links nutrition, metabolism, and immune homeostasis. Leptin is capable of modulating several immune responses. However, the effect of leptin on dendritic cells (DCs) has not yet been recognized. Because DCs are instrumental in the development of immune responses, in this study, we evaluated the impact of leptin on DC activation. We demonstrated the presence of leptin receptor in human immature and mature DCs both at mRNA and protein level and its capacity to transduce leptin signaling leading to STAT-3 phosphorylation. We found no consistent modulation of DC surface molecules known to be critical for their APC function in response to leptin. In contrast, we found that leptin induces rearrangement of actin microfilaments, leading to uropod and ruffle formation. At a functional level, leptin up-regulates the IL-1β, IL-6, IL-12, TNF-α, and MIP-1α production. Coincident with this, leptin-treated DCs stimulate stronger heterologous T cell responses. Furthermore, we found that leptin down-regulates IL-10 production by DCs and drives naive T cell polarization toward Th1 phenotype. Finally, we found that leptin partly protects DCs from spontaneous and UVB-induced apoptosis. Consistent with the antiapoptotic effect of leptin, we observed the activation of NF-κB and a parallel up-regulation of bcl-2 and bcl-xL gene expression. These results provide new insights on the immunoregulatory function of leptin demonstrating its ability to improve DC functions and to promote DC survival. This is of relevance considering a potential application of leptin in immunotherapeutic approaches and its possible use as adjuvant in vaccination protocols.
Impaired Transporter Associated with Antigen Processing-Dependent Peptide Transport during Productive EBV Infection
Authors: Ressing Maaike E. , Keating Sinéad E. , van Leeuwen Daphne , Koppers-Lalic Danijela , Pappworth Isabel Y. , Wiertz Emmanuel J. H. J. , Rowe Martin
Published: April 2014

Human herpesviruses, including EBV, persist for life in infected individuals. During the lytic replicative cycle that is required for the production of infectious virus and transmission to another host, many viral Ags are expressed. Especially at this stage, immune evasion strategies are likely to be advantageous to avoid elimination of virus-producing cells. However, little is known about immune escape during productive EBV infection because no fully permissive infection model is available. In this study, we have developed a novel strategy to isolate populations of cells in an EBV lytic cycle based on the expression of a reporter gene under the control of an EBV early lytic cycle promoter. Thus, induction of the viral lytic cycle in transfected EBV+ B lymphoma cells resulted in concomitant reporter expression, allowing us, for the first time, to isolate highly purified cell populations in lytic cycle for biochemical and functional studies. Compared with latently infected B cells, cells supporting EBV lytic cycle displayed down-regulation of surface HLA class I, class II, and CD20, whereas expression levels of other surface markers remained unaffected. Moreover, during lytic cycle peptide transport into the endoplasmic reticulum, was reduced to <30% of levels found in latent infection. Because steady-state levels of TAP proteins were unaffected, these results point toward EBV-induced interference with TAP function as a specific mechanism contributing to the reduced levels of cell surface HLA class I. Our data implicate that EBV lytic cycle genes encode functions to evade T cell recognition, thereby creating a window for the generation of viral progeny.
A Mutant Cell with a Novel Defect in MHC Class I Quality Control
Authors: York Ian A. , Grant Ethan P. , Dahl A. Maria , Rock Kenneth L.
Published: April 2014

COS7 (African Green Monkey kidney) cells stably transfected with the mouse MHC class I allele H-2Kb were mutagenized, selected for low surface expression of endogenous MHC class I products, and subcloned. A mutant cell line, 4S8.12, expressing very low surface MHC class I (∼5% of parental levels) was identified. This cell line synthesized normal levels of the MHC class I H chain and β2-microglobulin, as well as normal levels of TAP, tapasin, GRP78, calnexin, calreticulin, ERp57, and protein disulfide isomerase. Full-length OVA was processed to generate presented H-2Kb-SIINFEKL complexes with equal efficiency in wild-type and mutant cells, demonstrating that proteasomes, as well as TAP and tapasin, functioned normally. Therefore, all the known components of the MHC class I Ag presentation pathway were intact. Nevertheless, primate (human and monkey) MHC class I H chain and β2-microglobulin failed to associate to form the normal peptide-receptive complex. In contrast, mouse H chains associated with β2-microglobulin normally and bound peptide at least as well as in wild-type cells. The 4S8.12 cells provide strong genetic evidence for a novel component in the MHC class I pathway. This as-yet unidentified gene is important in early assembly of primate, but not mouse, MHC class I complexes.
In Situ Sensory Adaptation of Tumor-Infiltrating T Lymphocytes to Peptide-MHC Levels Elicits Strong Antitumor Reactivity
Authors: Dorothée Guillaume , Vergnon Isabelle , El Hage Faten , Chansac Béatrice Le Maux , Ferrand Vincent , Lécluse Yann , Opolon Paule , Chouaib Salem , Bismuth Georges , Mami-Chouaib Fathia
Published: April 2014

We have isolated from tumor-infiltrating lymphocytes (TIL) and PBL of a lung carcinoma patient several tumor-specific T cell clones displaying similar peptide-MHC tetramer staining and expressing a unique TCR. Although these clones elicited identical functional avidity and similar cytolytic potential, only T cell clones derived from TIL efficiently lysed autologous tumor cells. Interestingly, all of these clones expressed the same T cell surface markers except for the TCR inhibitory molecule CD5, which was expressed at much lower levels in TIL than in PBL. Video-imaging recordings demonstrated that, although both T cell clones could form stable conjugates with tumor cells, the Ca2+ response occurred in TIL clones only. Significantly, analysis of a panel of circulating clones indicated that antitumor cytolytic activity was inversely proportional to CD5 expression levels. Importantly, CD5 levels in TIL appeared to parallel the signaling intensity of the TCR/peptide-MHC interaction. Thus, in situ regulation of CD5 expression may be a strategy used by CTL to adapt their sensitivity to intratumoral peptide-MHC levels.
CD4 T Cell-Dependent Conditioning of Dendritic Cells to Produce IL-12 Results in CD8-Mediated Graft Rejection and Avoidance of Tolerance
Authors: Filatenkov Alexander A. , Jacovetty Erica L. , Fischer Ursula B. , Curtsinger Julie M. , Mescher Matthew F. , Ingulli Elizabeth
Published: April 2014

Rejection of ectopic heart transplants expressing OVA requires OVA-specific CD4 and CD8 T cells. In the absence of CD4 T cells, OVA-specific CD8 T cells proliferate and migrate to the graft, but fail to develop cytolytic functions. With CD4 T cells present, clonal expansion of the CD8 T cells is only marginally increased but the cells now develop effector functions and mediate rapid graft rejection. In the presence of CD4 T cells, Ag and B7 levels do not increase on dendritic cells but IL-12 production is up-regulated, and this requires CD154 expression on the CD4 T cells. OVA-specific CD8 T cells lacking the IL-12 receptor fail to differentiate or mediate graft rejection even when CD4 T cells are present. Thus, CD4 T cells condition dendritic cells by inducing the production of IL-12, which is needed as the “third signal” for CD8 T cell differentiation and avoidance of tolerance.
B Cells from Mice Prematurely Expressing Human Complement Receptor Type 2 Are Unresponsive to T-Dependent Antigens
Authors: Birrell Louise , Kulik Liudmila , Morgan B. Paul , Holers V. Michael , Marchbank Kevin J.
Published: April 2014

Complement receptor type 2 (CR2/CD21), in association with CD19, plays an important role in enhancing mature B cell responses to opsonized Ags. We have shown that mice expressing a human CR2/CD21 (hCR2/CD21) transgene during the CD43+/CD25− late pro-B cell stage of B cell development demonstrate marked changes in subsequent B cell ontogeny. In the present study, we show that the humoral immune response to the T cell-dependent Ag, sheep RBC, is muted severely in a manner inversely proportional to B cell expression level of hCR2. Individual Ag-specific IgG isotypes vary in the degree to which they are affected but all are reduced while IgM titers are normal. A substantial reduction in germinal centers, both in size and frequency, in the spleens of immunized hCR2 transgenic mice demonstrates a failure to maintain germinal center reaction. However, both IgM expression levels and LPS-proliferative responses appear fully intact in B cells from hCR2-positive mice, suggesting that this alteration in B cell phenotype is different qualitatively from that of specific Ag-defined anergy models. These data suggest that the unresponsiveness to T-dependent Ags displayed by hCR2-positive B cells is linked to an increase in the level of stimulus required to propel the B cell into a fully activated state and thus a normal humoral immune response to Ags. We conclude that this phenotype and these mice may offer an additional means to dissect mechanisms underlying B cell tolerance and Ag responsiveness both in bone marrow and periphery.
Cathepsin-L Influences the Expression of Extracellular Matrix in Lymphoid Organs and Plays a Role in the Regulation of Thymic Output and of Peripheral T Cell Number
Authors: Lombardi Gabriela , Burzyn Dalia , Mundiñano Juliana , Berguer Paula , Bekinschtein Pedro , Costa Hector , Castillo Lilian Fedra , Goldman Alejandra , Meiss Roberto , Piazzon Isabel , Nepomnaschy Irene
Published: April 2014

Nackt mice, which are deficient in cathepsin-L (CTSL), show an early impairment during positive selection in the context of class II MHC molecules and as a consequence, the percentage and absolute number of CD4+ thymocytes are significantly decreased. In this study, we show that lymph nodes from nackt mice are hypertrophied, showing normal absolute numbers of CD4+ T cells and marked increases in the number of CD8+ T lymphocytes. Basal proliferative levels are increased in the CD4+ but not in the CD8+ population. Lymph node T cells show increases in the expression of α5, α6, and β1 integrin chains. These alterations correlate with increases in the expression of extracellular matrix (ECM) components in lymph nodes. Interestingly, laminin, fibronectin, and collagen I and IV are markedly decreased in nackt thymus which shows an augmented output of CD8+ cells. These results demonstrate that a mutation in the Ctsl gene influences the levels of ECM components in lymphoid organs, the thymic output, and the number of T cells in the periphery. They further raise the possibility that, by regulating the level of expression of ECM components in lymphoid organs, CTSL is able to broadly affect the immune system.
CD229 (Ly9) Lymphocyte Cell Surface Receptor Interacts Homophilically through Its N-Terminal Domain and Relocalizes to the Immunological Synapse
Authors: Romero Xavier , Zapater Nuria , Calvo María , Kalko Susana G. , de la Fuente Miguel Angel , Tovar Victoria , Ockeloen Charlotte , Pizcueta Pilar , Engel Pablo
Published: April 2014

CD229 is a member of the CD150 family of the Ig superfamily expressed on T and B cells. Receptors of this family regulate cytokine production and cytotoxicity of lymphocytes and NK cells. The cytoplasmic tail of CD229 binds to SAP, a protein that is defective in X-linked lymphoproliferative syndrome. To identify the CD229 ligand, we generated a soluble Ig fusion protein containing the two N-terminal extracellular domains of human CD229 (CD229-Ig). CD229-Ig bound to CD229-transfected cells, whereas no binding was detected on cells expressing other CD150 family receptors, showing that CD229 binds homophilically. Both human and mouse CD229 interacted with itself. Domain deletion mutants showed that the N-terminal Ig-domain mediates homophilic adhesion. CD229-CD229 binding was severely compromised when the charged amino acids E27 and E29 on the predicted B-C loop and R89 on the F-G loop of the N-terminal domain were mutated to alanine. In contrast, one mutation, R44A, enhanced the homophilic interaction. Confocal microscopy image analysis revealed relocalization of CD229 to the contact area of T and B cells during Ag-dependent immune synapse formation. Thus, CD229 is its own ligand and participates in the immunological synapse.
The Radioprotective 105/MD-1 Complex Links TLR2 and TLR4/MD-2 in Antibody Response to Microbial Membranes
Authors: Nagai Yoshinori , Kobayashi Toshihiko , Motoi Yuji , Ishiguro Kohtaroh , Akashi Sachiko , Saitoh Shin-ichiroh , Kusumoto Yutaka , Kaisho Tsuneyasu , Akira Shizuo , Matsumoto Mitsuru , Takatsu Kiyoshi , Miyake Kensuke
Published: April 2014

Low-affinity IgG3 Abs to microbial membranes are important for primary immune defense against microbes, but little is known about the importance of TLRs in their production. IgG3 levels were extremely low in mice lacking radioprotective 105 (RP105), a B cell surface molecule structurally related to TLRs. RP105−/− B cells proliferated poorly in response to not only the TLR4 ligand LPS but also TLR2 ligand lipoproteins, both of which mediate the immunostimulatory activity of microbial membranes. RP105−/− mice were severely impaired in hapten-specific Ab production against LPS or lipoproteins. CD138 (syndecan-1)-positive plasma cells were detected after lipid A injection in wild-type spleen but much less in RP105−/− spleen. RP105 ligation in vivo induced plasma cell differentiation. RP105 expression was ∼3-fold higher on marginal zone B cells than on follicular and B1 cells and was down-regulated on germinal center cells. These results demonstrate that a signal via RP105 is uniquely important for regulating TLR-dependent Ab production to microbial membranes.
Dendritic Cell Maturation Induced by Muramyl Dipeptide (MDP) Derivatives: Monoacylated MDP Confers TLR2/TLR4 Activation
Authors: Uehori Junji , Fukase Koichi , Akazawa Takashi , Uematsu Satoshi , Akira Shizuo , Funami Kenji , Shingai Masashi , Matsumoto Misako , Azuma Ichiro , Toyoshima Kumao , Kusumoto Shoichi , Seya Tsukasa
Published: April 2014

6-O-acyl-muramyldipeptides (MDP) with various lengths of fatty acid chains were examined for their dendritic cell (DC) maturation activity expressed through TLRs. Judging from anti-TLR mAb/inhibitor-blocking analysis, MDP derivatives with a single octanoyl or stearoyl fatty acid chain were found to activate TLR2 and TLR4 on human DCs, although intact and diacylated MDP expressed no ability to activate TLRs. Human DC activation profiles by the monoacylated MDP were essentially similar to those by Calmette-Guérin (BCG)-cell wall skeleton (CWS) and BCG-peptidoglycan (PGN) based on their ability to up-regulate costimulators, HLA-DR, β2-microglobulin, and allostimulatory MLR. Monoacylated MDP induced cytokines with similar profiles to BCG-CWS or -PGN, although their potency for induction of TNF-α, IL-12p40, and IL-6 was less than that of BCG-CWS or -PGN. The MDP derivatives initiated similar activation in normal mouse macrophages, but exhibited no effect on TLR2/4-deficient or MyD88-deficient mouse macrophages. Mutation of d-isoGln to l-isoGln in monoacylated MDP did not result in loss of the DC maturation activity, suggesting marginal participation of nucleotide-binding oligomerization domain 2, if any, in monoacyl MDP-dependent DC maturation. These results define the adjuvant activity of 6-O-acyl MDP compounds at the molecular level. They target TLR2/TLR4 and act through the MyD88-dependent pathway in DCs and macrophages. Hence, the unusual combined activation of TLR2 and TLR4 observed with Mycobacterium tuberculosis is in part reflected in the functional properties of monoacylated MDP compounds. These findings infer that the essential minimal requirement for TLR2/4-mediated adjuvancy of BCG lies within a modified MDP.
Differential Immunogenicity of Two Peptides Isolated by High Molecular Weight-Melanoma-Associated Antigen-Specific Monoclonal Antibodies with Different Affinities
Authors: Luo Wei , Hsu Jeff Chi-feng , Tsao Chun-Yen , Ko Eric , Wang Xinhui , Ferrone Soldano
Published: April 2014

Peptide mimics isolated from phage display peptide libraries by panning with self-tumor-associated Ag (TAA)-specific mAbs are being evaluated as immunogens to implement active specific immunotherapy. Although TAA-specific mAb are commonly used to isolate peptide mimics, no information is available regarding the Ab characteristics required to isolate immunogenic TAA peptide mimics. To address this question, we have used mAb 763.74 and mAb GH786, which recognize the same or spatially close antigenic determinant(s) of the human high m.w.-melanoma-associated Ag (HMW-MAA), although with different affinity. mAb 763.74 affinity is higher than that of mAb GH786. Panning of phage display peptide libraries with mAb 763.74 and mAb GH786 resulted in the isolation of peptides P763.74 and PGH786, respectively. When compared for their ability to induce HMW-MAA-specific immune responses in BALB/c mice, HMW-MAA-specific Ab titers were significantly higher in mice immunized with P763.74 than in those immunized with PGH786. The HMW-MAA-specific Ab titers were markedly increased by a booster with HMW-MAA-bearing melanoma cells, an effect that was significantly higher in mice primed with P763.74 than in those primed with PGH786. Lastly, P763.74, but not PGH786, induced a delayed-type hypersensitivity response to HMW-MAA-bearing melanoma cells. These findings suggest that affinity for TAA is a variable to take into account when selecting mAb to isolate peptide mimics from a phage display peptide library.
Transcription Factor Tfec Contributes to the IL-4-Inducible Expression of a Small Group of Genes in Mouse Macrophages Including the Granulocyte Colony-Stimulating Factor Receptor
Authors: Rehli Michael , Sulzbacher Sabine , Pape Sabine , Ravasi Timothy , Wells Christine A. , Heinz Sven , Söllner Liane , El Chartouni Carol , Krause Stefan W. , Steingrimsson Eirikur , Hume David A. , Andreesen Reinhard
Published: April 2014

Expression of the mouse transcription factor EC (Tfec) is restricted to the myeloid compartment, suggesting a function for Tfec in the development or function of these cells. However, mice lacking Tfec develop normally, indicating a redundant role for Tfec in myeloid cell development. We now report that Tfec is specifically induced in bone marrow-derived macrophages upon stimulation with the Th2 cytokines, IL-4 and IL-13, or LPS. LPS induced a rapid and transient up-regulation of Tfec mRNA expression and promoter activity, which was dependent on a functional NF-κB site. IL-4, however, induced a rapid, but long-lasting, increase in Tfec mRNA, which, in contrast to LPS stimulation, also resulted in detectable levels of Tfec protein. IL-4-induced transcription of Tfec was absent in macrophages lacking Stat6, and its promoter depended on two functional Stat6-binding sites. A global comparison of IL-4-induced genes in both wild-type and Tfec mutant macrophages revealed a surprisingly mild phenotype with only a few genes affected by Tfec deficiency. These included the G-CSFR (Csf3r) gene that was strongly up-regulated by IL-4 in wild-type macrophages and, to a lesser extent, in Tfec mutant macrophages. Our study also provides a general definition of the transcriptome in alternatively activated mouse macrophages and identifies a large number of novel genes characterizing this cell type.
Sex-Specific Effect of Insulin-Dependent Diabetes 4 on Regulation of Diabetes Pathogenesis in the Nonobese Diabetic Mouse
Authors: Ivakine Evgueni A. , Fox Casey J. , Paterson Andrew D. , Mortin-Toth Steven M. , Canty Angelo , Walton David S. , Aleksa Katarina , Ito Shinya , Danska Jayne S.
Published: April 2014

Many human autoimmune diseases are more frequent in females than males, and their clinical severity is affected by sex hormone levels. A strong female bias is also observed in the NOD mouse model of type I diabetes (T1D). In both NOD mice and humans, T1D displays complex polygenic inheritance and T cell-mediated autoimmune pathogenesis. The identities of many of the insulin-dependent diabetes (Idd) loci, their influence on specific stages of autoimmune pathogenesis, and sex-specific effects of Idd loci in the NOD model are not well understood. To address these questions, we analyzed cyclophosphamide-accelerated T1D (CY-T1D) that causes disease with high and similar frequencies in male and female NOD mice, but not in diabetes-resistant animals, including the nonobese diabetes-resistant (NOR) strain. In this study we show by genetic linkage analysis of (NOD × NOR) × NOD backcross mice that progression to severe islet inflammation after CY treatment was controlled by the Idd4 and Idd9 loci. Congenic strains on both the NOD and NOR backgrounds confirmed the roles of Idd4 and Idd9 in CY-T1D susceptibility and revealed the contribution of a third locus, Idd5. Importantly, we show that the three loci acted at distinct stages of islet inflammation and disease progression. Among these three loci, Idd4 alleles alone displayed striking sex-specific behavior in CY-accelerated disease. Additional studies will be required to address the question of whether a sex-specific effect of Idd4, observed in this study, is also present in the spontaneous model of the disease with striking female bias.
Dendritic Cell-Intrinsic Expression of NF-κB1 Is Required to Promote Optimal Th2 Cell Differentiation
Authors: Artis David , Kane Colleen M. , Fiore James , Zaph Colby , Shapira Sagi , Joyce Karen , MacDonald Andrew , Hunter Christopher , Scott Phillip , Pearce Edward J.
Published: April 2014

A number of receptors and signaling pathways can influence the ability of dendritic cells (DC) to promote CD4+ Th type 1 (Th1) responses. In contrast, the regulatory pathways and signaling events that govern the ability of DC to instruct Th2 cell differentiation remain poorly defined. In this report, we demonstrate that NF-κB1 expression within DC is required to promote optimal Th2 responses following exposure to Schistosoma mansoni eggs, a potent and natural Th2-inducing stimulus. Although injection of S. mansoni eggs induced production of IL-4, IL-5, and IL-13 in the draining lymph node of wild-type (WT) mice, NF-κB1−/− hosts failed to express Th2 cytokines and developed a polarized Ag-specific IFN-γ response. In an in vivo adoptive transfer model in which NF-κB-sufficient OVA-specific DO11.10 TCR transgenic T cells were injected into OVA-immunized WT or NF-κB1−/− hosts, NF-κB1−/− APCs efficiently promoted CD4+ T cell proliferation and IFN-γ responses, but failed to promote Ag-specific IL-4 production. Further, bone marrow-derived DC from NF-κB1−/− mice failed to promote OVA-specific Th2 cell differentiation in in vitro coculture studies. Last, S. mansoni egg Ag-pulsed NF-κB1−/− DC failed to prime for Th2 cytokine responses following injection into syngeneic WT hosts. Impaired Th2 priming by NF-κB1−/− DC was accompanied by a reduction in MAPK phosphorylation in Ag-pulsed DC. Taken together, these studies identify a novel requirement for DC-intrinsic expression of NF-κB1 in regulating the MAPK pathway and governing the competence of DC to instruct Th2 cell differentiation.
Neutralizing Antibodies to Adenovirus Serotype 5 Vaccine Vectors Are Directed Primarily against the Adenovirus Hexon Protein
Authors: Sumida Shawn M. , Truitt Diana M. , Lemckert Angelique A. C. , Vogels Ronald , Custers Jerome H. H. V. , Addo Marylyn M. , Lockman Shahin , Peter Trevor , Peyerl Fred W. , Kishko Michael G. , Jackson Shawn S. , Gorgone Darci A. , Lifton Michelle A. , Essex Myron , Walker Bruce D. , Goudsmit Jaap , Havenga Menzo J. E. , Barouch Dan H.
Published: April 2014

The utility of recombinant adenovirus serotype 5 (rAd5) vector-based vaccines for HIV-1 and other pathogens will likely be limited by the high prevalence of pre-existing Ad5-specific neutralizing Abs (NAbs) in human populations. However, the immunodominant targets of Ad5-specific NAbs in humans remain poorly characterized. In this study, we assess the titers and primary determinants of Ad5-specific NAbs in individuals from both the United States and the developing world. Importantly, median Ad5-specific NAb titers were >10-fold higher in sub-Saharan Africa compared with the United States. Moreover, hexon-specific NAb titers were 4- to 10-fold higher than fiber-specific NAb titers in these cohorts by virus neutralization assays using capsid chimeric viruses. We next performed adoptive transfer studies in mice to evaluate the functional capacity of hexon- and fiber-specific NAbs to suppress the immunogenicity of a prototype rAd5-Env vaccine. Hexon-specific NAbs were remarkably efficient at suppressing Env-specific immune responses elicited by the rAd5 vaccine. In contrast, fiber-specific NAbs exerted only minimal suppressive effects on rAd5 vaccine immunogenicity. These data demonstrate that functionally significant Ad5-specific NAbs are directed primarily against the Ad5 hexon protein in both humans and mice. These studies suggest a potential strategy for engineering novel Ad5 vectors to evade dominant Ad5-specific NAbs.
Up-Regulation of the JAK/STAT1 Signal Pathway during Chlamydia trachomatis Infection
Authors: Lad Sonya P. , Fukuda Elaine Y. , Li Jiali , de la Maza Luis M. , Li Erguang
Published: April 2014

Chlamydia trachomatis infection is the most common cause of sexually transmitted disease, leading to female pelvic inflammatory disease and infertility. The disease process has been linked to cellular response to this bacterial pathogen. This obligate intracellular pathogen infects macrophages, fibroblast cells, and epithelial and endothelial cells. We show in this study that infection of cervical epithelial cells, the primary target of Chlamydia trachomatis, leads to up-regulation and activation of the JAK/STAT signal pathway. Specifically, Chlamydia trachomatis infection of HeLa 229 cells selectively induces STAT1, STAT2, and IFN-stimulated transcription factor 3γ expression and promotes STAT1 activation. The up-regulation of STAT1 is dependent on bacterial replication, because treatment of infected cells with antibiotics prevents STAT1 up-regulation. By analysis of the gene transcriptional and cytokine expression profiles of host cells combined with the use of neutralizing Abs, we show that IFN-β production is critical for STAT1 induction in epithelial cells. Finally, we demonstrate that the host up-regulates STAT1 to restrict bacterial infection, because Chlamydia propagates more efficiently in STAT1-null or STAT1 knockdown cells, whereas Chlamydia growth is inhibited in cells with up-regulated STAT1 expression. This study demonstrates that the infected cells up-regulate the host innate antimicrobial response to chlamydial infection. It also highlights the importance of cellular response by nonimmune cells in host clearance of chlamydial infection.
Immune-Reconstituted Influenza Virosome Containing CD40L Gene Enhances the Immunological and Protective Activity of a Carcinoembryonic Antigen Anticancer Vaccine
Authors: Cusi Maria Grazia , Del Vecchio Maria Teresa , Terrosi Chiara , Savellini Gianni Gori , Di Genova Giuseppa , La Placa Marco , Fallarino Francesca , Moser Christian , Cardone Concetta , Giorgi Giorgio , Francini Guido , Correale Pierpaolo
Published: April 2014

The correct interaction of a costimulatory molecule such as CD40L with its contrareceptor CD40 expressed on the membrane of professional APCs, provides transmembrane signaling that leads to APC activation. This process can be exploited to significantly improve the efficacy of cancer vaccines and the outcome of a possible cancer vaccine-induced, Ag-specific CTL response. Therefore, we investigated whether a novel intranasal delivery of immune-reconstituted influenza virosomes (IRIV), assembled with the CD40L gene (CD40L/IRIV), could be used to improve protective immunity and the Ag-specific CTL response against carcinoembryonic Ag (CEA) generated with a novel vaccine constituted of IRIV assembled with the CEA gene (CEA/IRIV). Our results suggest that CD40L/IRIV was able to augment CEA-specific CTL activity and CEA-specific protective immunity induced by CEA/IRIV most likely through the induction of a CTL response associated with a Th1 phenotype. In conclusion, we provide evidence that CD40L/IRIV, by acting through the CD40L/CD40 signaling pathway, acts as an immune-adjuvant that could increase the efficacy of a CEA-specific cancer vaccine, which could provide an efficacious new strategy for cancer therapy.
A Lymphotoxin-IFN-β Axis Essential for Lymphocyte Survival Revealed during Cytomegalovirus Infection
Authors: Banks Theresa A. , Rickert Sandra , Benedict Chris A. , Ma Lisa , Ko Mira , Meier Joshua , Ha Won , Schneider Kirsten , Granger Steven W. , Turovskaya Olga , Elewaut Dirk , Otero Dennis , French Anthony R. , Henry Stanley C. , Hamilton John D. , Scheu Stefanie , Pfeffer Klaus , Ware Carl F.
Published: April 2014

The importance of lymphotoxin (LT) βR (LTβR) as a regulator of lymphoid organogenesis is well established, but its role in host defense has yet to be fully defined. In this study, we report that mice deficient in LTβR signaling were highly susceptible to infection with murine CMV (MCMV) and early during infection exhibited a catastrophic loss of T and B lymphocytes, although the majority of lymphocytes were themselves not directly infected. Moreover, bone marrow chimeras revealed that lymphocyte survival required LTα expression by hemopoietic cells, independent of developmental defects in lymphoid tissue, whereas LTβR expression by both stromal and hemopoietic cells was needed to prevent apoptosis. The induction of IFN-β was also severely impaired in MCMV-infected LTα−/− mice, but immunotherapy with an agonist LTβR Ab restored IFN-β levels, prevented lymphocyte death, and enhanced the survival of these mice. IFN-αβR−/− mice were also found to exhibit profound lymphocyte death during MCMV infection, thus providing a potential mechanistic link between type 1 IFN induction and lymphocyte survival through a LTαβ-dependent pathway important for MCMV host defense.