bluuebunny/crossref_metadata_2025 huggingface dataset:
Blood‐ and skin‐derived monocytes/macrophages respond to C3a but not to C3a(desArg) with a transient release of calcium via a pertussis toxin‐sensitive signal transduction pathway
Authors: Zwirner Jörg , Götze Otto , Moser Alexander , Sieber Anja , Begemann Gabriele , Kapp Alexander , Elsner Jörn , Werfel Thomas
Published: March 2007

Controversial results have been published in the past regarding the functional reactivity of monocytes (Mo) and macrophages (Mϕ) to the anaphylatoxin C3a and its degradation product C3a(desArg). In this study we performed binding and calcium mobilization experiments with recombinant human C3a (rC3a) and rC3a(desArg). Blood Mo displayed non‐inhibitable binding of FITC‐labeled rC3a (rC3aFITC) but responded to rC3a with a transient release of the intracellular calcium concentration ([Ca2+]i), whereas rC3a(desArg) was completely inactive. In contrast, binding of rC3aFITC to eosinophilic granulocytes and the mast cell line HMC‐1 which have been shown previously to express C3a binding sites could be blocked by a monoclonal anti‐C3a antibody. The rC3a‐induced [Ca2+]i release in blood Mo was pertussis toxin (PTX)‐sensitive suggesting the involvement of G‐proteins in the signal transduction pathway. Skin‐derived Mo/Mϕ reacted similarly to blood Mo as no specific binding of rC3aFITC to these cells could be demonstrated, whereas an intracellular release of calcium ions in response to the anaphylatoxin was observed. Homologous desensitization to rC3a but not heterologous desensitization to rC5a was detected in further experiments. The functional effect of C3a, but not the unspecific binding of rC3aFITC blood Mo and skin‐derived Mo/Mϕ could be blocked by the monoclonal anti‐C3a antibody. These results suggest the expression of the recently cloned G‐protein‐coupled receptor for C3a on human blood Mo and skin‐derived Mo/Mϕ. However, the total number of specific C3a binding sites on these cells is distinctly lower as compared to eosinophilic granulocytes and cells of the mast cell line HMC‐1. The small number of C3a receptors on Mo/Mϕ may be masked by a pronounced non‐inhibitable binding of rC3aFITC. This binding, however, may contribute to the recently described biological effects of C3a(desArg) on Mo.
Deviation of pancreas‐infiltrating cells to Th2 by interleukin‐12 antagonist administration inhibits autoimmune diabetes
Authors: Trembleau Sylvie , Penna Giuseppe , Gregori Silvia , Gately Maurice K. , Adorini Luciano
Published: March 2007

Nonobese diabetic (NOD) mice develop spontaneous insulin‐dependent diabetes mellitus (IDDM), and the pancreas‐infiltrating T cells invariably show a Th1 phenotype. We demonstrated here that the interleukin (IL)‐12 antagonist (p40)2 can deviate the default Th1 development of naive T cell receptor (TCR)‐transgenic CD4+ cells to the Th2 pathway in vitro. Although (p40)2 does not modify the cytokine profile of polarized Th1 cells, it prevents further recruitment of CD4+ cells into the Th1 subset. To study the involvement of Th1 and Th2 cells in the initiation and progression of IDDM, we targeted endogenous IL‐12 by administration of (p40)2 in NOD mice. (p40)2 administration to NOD mice inhibits interferon‐γ but not IL‐10 production in response to lipopolysaccharide (LPS) or to the putative autoantigen IA‐2. Serum immunoglobulin isotypes determined after (p40)2 treatment indicate an increase in Th2 and a decrease in Th1 helper activity. Administration of (p40)2 from 3 weeks of age onwards, before the onset of insulitis, results in the deviation of pancreas‐infiltrating CD4+ but not CD8+ cells to the Th2 phenotype as well as in the reduction of spontaneous and cyclophosphamide‐accelerated IDDM. After treating NOD mice with (p40)2 from 9 weeks of age, when insulitis is well established, few Th2 and a reduced percentage of Th1 cells are found in the pancreas. This is associated with a slightly decreased incidence of spontaneous IDDM, but no protection from cyclophosphamide‐accelerated IDDM. In conclusion, deviation of pancreas‐infiltrating CD4+ cells to Th2 is associated with protection from IDDM. However, targeting IL‐12 after the onset of insulitis, when the pancreas contains polarized Th1 cells, is not sufficient to induce an effective immune deviation able to significantly modify the course of disease.
Presentation of a viral peptide assembled on the carbohydrate moieties of immunoglobulin does not require processing
Authors: Brumeanu Teodor‐D. , Casares Sofia , Dehazya Philip , Bot Simona , Bona Constantin A.
Published: March 2007

We have previously demonstrated that an immunodominant CD4 T cell epitope, HA110‐120 of the hemagglutinin (HA) of the A/PR/8/34 influenza virus, enzymatically assembled on the carbohydrate moieties of self immunoglobulins (Ig) primed the precursors of peptide‐specific T cells and induced efficient proliferation in vivo of naive lymphocytes from transgenic mice expressing the peptide‐specific T cell receptor. Here, we show that an immuno‐galacto‐peptide construct, IgG‐gal‐HA, does not require intracellular or extracellular processing to present the peptide to the specific T cells. The presentation occurs following the binding of the IgG‐gal‐HA construct to Fcγ receptor on the surface of antigen‐presenting cells (APC), with concurrent interaction of the peptides to their neighboring major histocompatibility complex class II molecules. This mechanism of peptide presentation may harness the immune response in vivo by the engagement of APC with a low capacity of antigen processing, such as neonatal B cells. In addition, the enzymatic method of assembling various aminated compounds on the sugar moieties of Ig may offer novel perspectives on immunotargeting of antagonist peptides, cytostatic drugs, and biologically active ligands of therapeutic use.
The mannose receptor functions as a high capacity and broad specificity antigen receptor in human dendritic cells
Authors: Engering Anneke J. , Cella Marina , Fluitsma Donna , Brockhaus Manfred , Hoefsmit Elizabeth C. M. , Lanzavecchia Antonio , Pieters Jean
Published: March 2007

Dendritic cells, in contrast to B lymphocytes, must be able to efficiently internalize a diverse array of antigens for processing and loading onto major histo‐compatibility complex (MHC) class II molecules. Here we characterize the mannose receptor pathway in dendritic cells and show that mannose receptor‐mediated uptake of antigens results in a ∼ 100‐fold more efficient presentation to T cells, as compared to antigens internalized via fluid phase. Immunocytochemistry as well as subcellular fractionation revealed the localization of the mannose receptor and MHC class II molecules in distinct subcellular compartments. The mannose receptor thus functions in rapid internalization and concentration of a variety of glycosylated antigens that become available for processing and presentation. This may contribute to the unique capacity of dendritic cells to generate primary T cell responses against infectious agents.
Identification and analysis of a novel member of the ubiquitin family expressed in dendritic cells and mature B cells
Authors: Bates Elizabeth E. M. , Ravel Odile , Dieu Marie‐Caroline , Ho Stephen , Guret Christiane , Bridon Jean‐Michel , Ait‐Yahia Smina , Brière Francine , Caux Christophe , Banchereau Jacques , Lebecque Serge
Published: March 2007

Using a cDNA subtraction technique, a novel member of the ubiquitin family was isolated from human dendritic cells. This gene encodes a diubiquitin protein containing tandem head to tail ubiquitin‐like domains, with the conservation of key functional residues. Expression of this 777‐bp mRNA was restricted to dendritic cells and B cells, with strong expression in mature B cells. Southern blot analysis indicated that a single copy of this gene is present. In situ hybridization on tonsillar tissue showed expression in epithelial cells and isolated cells within the germinal center. With respect to an expressed‐sequence tag (EST) this cDNA could be localized to the major histocompatibility complex class I region of chromosome 6. Comparative analysis and the expression pattern of this gene suggests a function in antigen processing and presentation.
Biochemical characterization of the human diabetes‐associated HLA‐DQ8 allelic product: Similarity to the major histocompatibility complex class II I‐Ag7 protein of non‐obese diabetic mice
Authors: Reizis Boris , Altmann Daniel M. , Cohen Irun R.
Published: March 2007

The human HLA‐DQ8 (A1*0301/B1*0302) allelic product manifests a strong association with insulin‐dependent diabetes mellitus (IDDM). Previous biochemical studies of the major histocompatibility complex (MHC) class II I‐Ag7 protein of IDDM‐prone non‐obese diabetic mice produced controversial results. To better define the biochemical properties of IDDM‐associated MHC class II molecules, we analyzed DQ8 proteins, in comparison to other DQ allelic products, by partially denaturing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE). We now report that DQ8 proteins have a normal peptide occupancy and lifespan in cells. Similar to I‐Ag7, DQ8 proteins formed only a minor fraction of SDS‐stable complexes with peptides. Although this phenotype was not unique to DQ8, some DQ allelic products such as IDDM‐protective DQ6 proteins were SDS resistant. The DQ9 allelic product, differing from DQ8 only at position (P) β57, was SDS stable, suggesting that non‐Asp residues at β57 might decrease the SDS stability of DQ proteins. We identified a single peptide which specifically induced an SDS‐stable conformation in DQ8 as well as in I‐Ag7 molecules. The residues at anchor P1 in this peptide were found to influence the SDS stability of both molecules. Together with our previous observation of similar binding motifs of I‐Ag7 and DQ8, these results demonstrate an overall biochemical similarity of mouse and human diabetes‐associated MHC class II molecules. This similarity might contribute to a common immunological mechanism of IDDM in both species.
Anterior chamber inoculation of splenocytes without Fas/Fas‐ligand interaction primes for a delayed‐type hypersensitivity response rather than inducing anterior chamber‐associated immune deviation
Authors: Kawashima Hidetoshi , Yamagami Satoru , Tsuru Tadahiko , Gregerson Dale S.
Published: March 2007

The inoculation of antigens into the anterior chamber (AC) of the eye induces an antigen‐specific immune response that inhibits delayed‐type hypersensitivity (DTH). This regulatory response is known as anterior chamber‐associated immune deviation (ACAID). The ACAID response appears to be complex, as it can be elicited by a wide variety of soluble and cell‐associated antigens, including foreign, self, tumor, and alloantigens. To evaluate the contribution of Fas/Fas ligand (FasL) interaction to the induction of ACAID to alloantigens, gld and lpr mutant mice were used in conjunction with normal C3H, MRL, and BALB/c mice. ACAID was induced by inoculation of non‐irradiated splenocytes from donor mice into the AC of various recipients. After 1 week, recipients were primed intradermally with donor splenocytes. One week later DTH was measured by ear swelling. C3Hgld mutants lacking functional FasL did not develop ACAID after the AC inoculation of BALB/c splenocytes. Conversely, the AC inoculation sensitized these mutants. MRLlpr mutants, which lack Fas, developed ACAID following inoculation of BALB/c cells. AC inoculation of lpr splenocytes did not induce ACAID, but sensitized C3H recipients. Treatment of the AC inoculum with an anti‐Fas antibody blocked ACAID induction in a transient manner, as the recipients developed ACAID later. These results show that interaction of the Fas and FasL is required to induce ACAID to allogeneic cells. In the absence of Fas expression on donor splenocytes, or FasL expression by the recipient, AC inoculation primes for a DTH response rather than inducing ACAID.
Neutrophil Fcγ and complement receptors involved in binding soluble IgG immune complexes and in specific granule release induced by soluble IgG immune complexes
Authors: Voice Julia Kate , Lachmann Peter Julius
Published: March 2007

We examined the effect of soluble IgG immune complex (IC) characteristics on the binding of IC to human neutrophils and IC‐induced specific granule release of neutrophils via Fcγ receptors (CD16 and CD32) and complement receptors (CR1 and CR3). A set of soluble IgG IC varying in size, IgG subclass, antigen epitope density and complement (C) incorporation were formed between 5‐iodo‐4‐hydroxy‐3‐nitrophenacetyl (NIP) coupled to bovine serum albumin (BSA) and chimeric mouse‐human anti‐NIP monoclonal antibodies (mAb) of all four IgG subclasses. High and low epitope density IC of all four IgG subclasses induced specific granule release with C, but in the absence of C only IgG1 and IgG3 IC were functionally active. The Fcγ and C receptors responsible for IgG IC‐induced specific granule release and IC binding were determined using mAb specific for the ligand binding sites of CD16, CD32 and CR3, and recombinant soluble CR1. Each defined IC displayed a unique pattern of receptor preference, dependent upon subclass and antigenic epitope density. IC binding and IC‐induced specific granule release was not mediated by the same receptor, or combination of receptors. High and low epitope density IgG3 IC binding and induction of specific granule release was mediated predominantly via CD16. Other IC subclasses bound differently, i.e. IgG1 IC used CD16 and CR3; IgG2 and IgG4 predominantly used complement receptors; but all three induced specific granule release via CD32. In vivo these results may translate into differential activation of neutrophils by soluble IC dependent upon their characteristics, leading to subtle nuances in the etiology, pathology and control of the immune response in IC‐related diseases.
Homotypic interaction of the heat‐stable antigen is not responsible for its co‐stimulatory activity for T cell clonal expansion
Authors: Zhou Qunmin , Wu Yan , Nielsen Peter J. , Liu Yang
Published: March 2007

The heat‐stable antigen (HSA) is an important co‐stimulatory molecule on antigen‐presenting cells (APC). However, the receptor on T cells that receives the co‐stimulatory signal from HSA has not been identified. Because the HSA is transiently expressed on T cells after the T cell receptor/CD3 complex is engaged, and because it can bind to itself in a homotypic fashion, it has been proposed that homotypic interaction of HSA is responsible for its co‐stimulatory activity. Here we test this hypothesis using mice that have a targeted mutation of the HSA gene, as well as novel transgenic mice that constitutively express HSA on T cells. We show that HSA‐deficient T cells remain responsive to co‐stimulation by HSA. Furthermore, constitutive expression of HSA does not enhance T cell response to co‐stimulatory by HSA. Taken together, our results demonstrate that homotypic interaction of HSA is not responsible for co‐stimulation mediated by HSA expressed on APC.
The mast cell function‐associated antigen exhibits saccharide binding capacity
Authors: Binsack Ralf , Pecht Israel
Published: March 2007

The mast cell function‐associated antigen (MAFA) is a membrane glycoprotein first identified on rat mucosal type mast cells (line RBL‐2H3) and known to inhibit the FcεRI‐mediated secretory response. In its extracellular domain, an amino acid stretch homologous to the carbohydrate binding domain of calcium‐dependent animal lectins has been found. To investigate its carbohydrate binding capacity, the MAFA has been expressed in the Spodoptera frugiperda insect cell line (Sf9) using the baculovirus expression system. Analysis by flow cytometry and surface labeling with 125I showed that the recombinant MAFA (rMAFA) was expressed as a monomeric and disulfide‐linked homodimeric glycoprotein in the membrane of the insect cells, and both forms exhibited the same epitopes as the protein isolated from RBL‐2H3 cells. Immunoaffinity‐purified rMAFA was then employed for studies of its saccharide binding capacity by using different neoglycans and glycoproteins. The rMAFA was found to bind specifically terminal mannose residues in a Ca2+‐dependent manner. These results support the notion that the extracellular domain of the MAFA is indeed able to bind ligands, which may be modulatory for the mast cell response.
MUC1 peptide epitopes associated with five different H‐2 class I molecules
Authors: Apostolopoulos Vasso , Haurum John S. , McKenzie Ian F. C.
Published: March 2007

We have previously described the induction of murine CD8+ major histocompatibility complex (MHC) class I‐restricted cytotoxic T cells (CTL) recognizing the 20‐amino acid repeat region of the human mucin 1 (MUC1) variable number of tandem repeats region (VNTR), a mucin greatly increased in expression in breast cancer and proposed as a target for immunotherapy. In that study, CTL could detect MUC1 peptides associated with the MHC of all nine strains examined, and we now report the different epitopes presented by five different MHC class I molecules. The epitopes were defined in CTL assays using peptide‐pulsed phytohemagglutinin blasts or MHC class I‐transfected L cells as targets; in addition, peptide binding assays and T cell proliferation studies were performed. Within the 20‐amino acid VNTR, nine potential epitopes could be defined. The epitopes for the four MHC class I molecules [Kb (three epitopes), Dd, Ld and Kk] were closely related, all containing the amino acids PDTRPAP. For Db, three epitopes were identified, all containing APGSTAP. Most of the epitopes did not contain a consensus motif for the particular MHC class I allele, and bound with low ‘affinity’, compared with known high‐affinity peptides. CD8+ T cell proliferation also occurred to the same MHC class I‐presented epitopes. Finally, when conventional anchor residues were introduced into the peptides, peptide binding increased, whereas CTL recognition was either retained (Kb) or lost (Db) depending on the epitope.
Down‐regulation of the major circulating precursors of proteins deposited in secondary amyloidosis by a recombinant mouse interleukin‐1 receptor antagonist
Authors: Grehan Sharon , Herbert Jeff , Whitehead Alexander S.
Published: March 2007

An inflammatory response was induced in C57BL/6 mice using silver nitrate. Co‐administration of a recombinant mouse interleukin‐1 receptor antagonist (rmIL‐1ra) significantly reduced the magnitude of hepatic induction of the mRNA specifying the serum amyloid A (A‐SAA) isoforms A‐SAA1 and A‐SAA2 for up to 24 h. In relative terms, the amount by which the induction of serum A‐SAA protein levels could be countered by the antagonist was less, probably reflecting extrahepatic A‐SAA synthesis that is regulated independently of IL‐1. Induction of hepatic serum amyloid P component (SAP) mRNA and other acute‐phase reactant (APR) mRNA were all partially blocked by rmIL‐1ra for up to 24 h, indicating that induction of these APR mRNA involves both IL‐1 and additional factors acting independently of IL‐1. Hepatic mRNA levels of the negative APR apolipoprotein A‐I (apo A‐I) and serum albumin were down‐regulated by silver nitrate treatment; rmIL‐1ra partially restored serum albumin mRNA levels but not those of apo A‐I. The IL‐1ra‐mediated reduction in inflammation‐induced hepatic mRNA and serum protein concentrations of A‐SAA and SAP (the precursors of the main protein components of amyloid deposits in secondary amyloidosis) was, however, not sufficient to prevent or delay early amyloid deposition in the silver nitrate/amyloid enhancing factor model of accelerated amyloidosis. The rmIL‐1ra may be a useful component in future therapies to control inflammation and secondary amyloidosis; in addition, it will be a useful tool for the detailed analysis of the IL‐1‐driven aspects of inflammation per se.
Human recombinant interferon‐β influences T helper subset differentiation by regulating cytokine secretion pattern and expression of homing receptors
Authors: McRae Bradford L. , Picker Louis J. , van Seventer Gijs A.
Published: March 2007

Type I interferons (IFN) are important regulators of both innate and acquired immunity. We have used an in vitro system of human CD4+ T cell differentiation to determine how IFN‐β influences development of T helper (Th) subsets and homing receptor expression. IFN‐β promoted differentiation of CD4+ T cells that produce low levels of both IFN‐γ and lymphotoxin compared to interleukin (IL)‐12‐derived Th1 CD4+ T cells. IFN‐β inhibited production of Th2 cytokines (IL‐5 and IL‐13) and augmented IL‐12‐mediated IL‐10 secretion. In addition, IFN‐β significantly enhanced L‐selectin expression on CD4+ T cells and synergized with IL‐12 to induce expression of cutaneous lymphocyte‐associated antigen (CLA). This Th1 L‐selectin+, CLA+ phenotype is characteristic of T cells found in normal human skin and suggests a role for type I IFN in the regulation of Th subset differentiation and tissue‐specific homing receptors.
Interleukin‐12 up‐regulates the induction of an antigen‐specific antibody response in cultures of human lymphocytes
Authors: Luzzati Alma L. , Giordani Luciana , Giacomini Elena
Published: March 2007

The influence of interleukin‐12 (IL‐12) on the induction of a specific antibody response to the T‐dependent antigen sheep erythrocytes (SRBC) in cultures of human blood lymphocytes was investigated. The response, evaluated as number of antigen‐induced antibody‐producing cells, was greatly increased in the presence of IL‐12. When a two‐stage limiting dilution culture system was used, the plot of the number of seeded cells versus the logarithm of the fraction of negative cultures deviated from linearity in antigen‐ and IL‐12‐stimulated cultures. However, linearity was reached when IL‐2 was added in the second stage. Under these latter conditions, since single‐hit criteria were fulfilled, it was possible to estimate the frequency of SRBC‐specific B cell precursors able to respond to the antigen and to show that such frequency was increased upon addition of IL‐12. Thus, the enhancing effect of IL‐12 may be based on an increased frequency of responding precursor cells. The results here presented demonstrate, to our knowledge for the first time, a definite role of IL‐12 in the induction of a specific antibody response in human cells. Further, they stress the importance for such studies of appropriate in vitro systems. Finally, they show that the induction of primary immune responses in cultures of human peripheral blood lymphocytes mostly depends on the proper cytokine balance at different time points.
Genetically modified bone marrow‐derived dendritic cells expressing tumor‐associated viral or “self” antigens induce antitumor immunity in vivo
Authors: Tüting Thomas , Deleo Albert B. , Lotze Michael T. , Storkus Walter J.
Published: March 2007

The clinical application of synthetic tumor peptide‐based vaccines is currently limited to patients with specified major histocompatibility complex (MHC) class I alleles. Such logistic limitations may be overcome using tumor gene‐based approaches. Here we describe the effective generation of dendritic cells (DC) expressing tumor peptide‐MHC complexes as a result of particle‐mediated transfer of genes encoding tumor‐associated antigens (TAA). Bone marrow‐derived DC were transfected with plasmid DNA encoding the tumor‐associated viral antigen E7 derived from human papilloma virus (HPV) 16. When applied as a vaccine, these genetically modified DC induced antigen‐specific CD8+ cyto‐toxic T lymphocytes (CTL) in vivo and promoted the rejection of a subsequent, normally lethal challenge with an HPV 16‐transformed tumor cell line. Of greatest interest, immunization of mice with syngeneic DC genetically modified to enhance their presentation of a constitutive “self” epitope derived from the tumor‐suppressor gene product p53 caused a significant reduction in the in vivo growth of a chemically induced p53‐positive sarcoma. These results suggest that cancer vaccines consisting of DC genetically modified to express TAA of viral or “self” origin effectively induce antitumor immunity in vivo.
Granulocyte‐macrophage colony‐stimulating factor induces a unique set of STAT factors in murine dendritic cells
Authors: Welte Thomas , Koch Franz , Schuler Gerold , Lechner Judith , Doppler Wolfgang , Heufler Christine
Published: March 2007

Cytokine‐mediated signaling pathways were studied in mouse dendritic cells (DC) by analysis of the activation pattern of STAT factors. Electrophoretic mobility shift assays were performed to detect STAT isoform‐specific complexes. Granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) simultaneously induced complexes containing STAT1, STAT3, STAT5A, STAT5B and STAT6. In non‐DC, a similar broad activation pattern of STAT factors by GM‐CSF or other cytokines has not been observed so far. By comparison, in peritoneal macrophages, GM‐CSF induced a complex with the properties of a truncated form of STAT5. Other cytokines tested on DC either failed to induce STAT factors [interleukin (IL)‐1β, IL‐2, IL‐15], or activated the same STAT factors as observed in peritoneal macrophages (IL‐4, IFN‐γ). Our results implicate a specific effect of GM‐CSF on STAT signaling in DC which might account for the cell type‐specific effect of this cytokine on development and function.
In vitro cell death of activated lymphocytes in Omenn's syndrome
Authors: Brugnoni Duilio , Airò Paolo , Facchetti Fabio , Blanzuoli Laura , Ugazio Alberto G. , Cattaneo Roberto , Notarangelo Luigi D.
Published: March 2007

Omenn's syndrome (OS) is characterized by erythrodermia, hepatosplenomegaly, lymphadenopathy, hypereosinophilia and elevated IgE levels associated with increased susceptibility to severe infections. Peripheral blood T cells, though usually present in normal number, show an activated phenotype (including an increased expression of CD95/Fas), a Th2 pattern of cytokine secretion and defective proliferative response to mitogens. In this report, we demonstrate that T cells from patients with OS undergo an excessive cell death in vitro resulting from two mechanisms. First, a substantial number of peripheral blood lymphocytes from OS patients die in unstimulated cultures (p = 0.009 vs. healthy controls). This spontaneous apoptosis is associated with reduced expression of bcl‐2 gene product (p < 0.05) and can be prevented by addition of interleukin (IL)‐2 (which also prevents down‐modulation of bcl‐2), while is independent from CD95 signaling. Second, lymphocytes from OS patients are highly susceptible to activation‐induced cell death (AICD) induced with mitogens. This mechanism is largely independent from IL‐2, while it can be significantly inhibited blocking CD95 with an IgG2b monoclonal antibody (mAb). The dependence of AICD from signals transduced via CD95 was confirmed showing that cross‐linking CD95 with an IgM mAb induces a higher cell death in purified CD4+ CD45RO+ cells from OS patients than in controls (comparable for CD95 expression). Both mechanisms of cell death observed in this study result from lymphocyte hyperactivation occurring in vivo in these patients and may contribute to functional T cell defects of OS.
Control of self‐reactive cytotoxic T lymphocytes expressing γδ T cell receptors by natural killer inhibitory receptors
Authors: Halary Franck , Peyrat Marie‐Alix , Champagne Eric , Lopez‐Botet Miguel , Moretta Alessandro , Moretta Lorenzo , Vié Henri , Fournié Jean‐Jacques , Bonneville Marc
Published: March 2007

The majority of peripheral blood γδ T cells in human adults expresses T cell receptors (TCR) with identical V regions (Vγ9 and Vδ2). These Vγ9Vδ2 T cells recognize the major histocompatibility complex (MHC) class I‐deficient B cell line Daudi and broadly distributed nonpeptidic antigens present in bacteria and parasites. Here we show that unlike αβ or Vγ9− γδ T cells, the majority of Vγ9Vδ2T cells harbor natural killer inhibitory receptors (KIR) (mainly CD94/NKG2A heterodimers), which are known to deliver inhibitory signals upon interaction with MHC class I molecules. Within Vγ9δ2 T cells, KIR were mainly expressed by clones exhibiting a strong lytic activity against Daudi cells. In stark contrast, almost all Vγ9Vδ2 T cell clones devoid of killing activity were KIR−, thus suggesting a coordinate acquisition of KIR and cytotoxic activity within Vγ9Vδ2 T cells. In functional terms, KIR inhibited lysis of MHC class I‐positive tumor B cell lines by Vγ9Vδ2 cytotoxic T lymphocytes (CTL) and raised their threshold of activation by microbial antigens presented by MHC class I‐positive cells. Furthermore, masking KIR or MHC class I molecules revealed a TCR‐dependent recognition by Vγ9Vδ2 CTL of ligands expressed by activated T lymphocytes, including the effector cells themselves. Taken together, these results suggest a general implication of Vγ9Vδ2 T cells in immune response regulation and a central role of KIR in the control of self‐reactive γδ CTL.
Cloning of NKG2‐F, a new member of the NKG2 family of human natural killer cell receptor genes
Authors: Plougastel Béatrice , Trowsdale John
Published: March 2007

The NKG2 family of genes encodes at least four different type II transmembrane molecules (NKG2‐A, NKG2‐B, NKG2‐C and NKG2‐E) which contain a C‐lectin domain. These proteins have been shown to be covalently associated with CD94, another C‐type lectin member. The heterodimers are involved in natural killer cell‐mediated recognition of different HLA‐allotypes. Here we describe the cloning of a new NKG2‐related gene, termed NKG2‐F, localized 25 kb from NKG2‐A as well as its relationship with the previously described NKG2‐D cDNA. Despite the similarities with the other NKG2 genes, NKG2‐F encodes a putative protein which does not contain any lectin domain. However, a conserved 24‐amino acid sequence, present in all members of the NKG2 family, suggests that NKG2‐F is also able to form heterodimers with CD94.
Influence of complement on the allospecific antibody response to a primary vascularized organ graft
Authors: Pratt Julian R. , Harmer Andrea W. , Levin James , Sacks Steven H.
Published: March 2007

The induction of antibody responses against T cell‐dependent antigens has been reported to be influenced by complement. We therefore asked if the primary induction of alloantibodies against transplantation antigens, an important determinant of transplant outcome, is complement sensitive and whether this has functional implications. We transplanted rat kidney allografts into fully major histocompatibility complex‐mismatched recipients, in which complement activation was inhibited by daily injection of soluble recombinant human complement receptor type 1 (sCR1). Control allograft recipients were injected with saline. Animals in the control group showed a marked antibody response against donor‐specific antigens and an increase in the proportion of activated B and T splenocytes by day 5 after transplantation. Complement‐inhibited rats showed a reduced level of antibody binding on target cells sharing the same histocompatibility antigens as the donor strain (p< 0.001), and a reduced level of activated splenic B (p< 0.01) and T (p< 0.01) cells. In a functional assay, the plasma of complement‐inhibited rats showed reduced cytotoxic activity against donor‐specific cells, and their grafts contained less bound antibody than controls. Analysis beyond 6 days was obscured due to the development of antibodies against sCR1. We conclude that complement activation facilitates the induction of the alloantibody response. Sparing of vascular injury and prolongation of graft survival, previously reported in complement‐inhibited rats (Pratt J. R. et al.,Am. J. Path.1996,149: 2055), could therefore be due to down‐regulation of the B cell response as well as reduced complement‐dependent cytotoxicity. Inhibition of complement may provide an ancillary approach to the prevention of allospecific antibody formation and the prolongation of allograft survival in primary kidney grafting.
T helper cell priming of mice to Borrelia burgdorferi Osp A leads to induction of protective antibodies following experimental but not tickborne infection
Authors: Zhong Weimin , Gern Lise , Kramer Michael , Wallich Reinhard , Simon Markus M.
Published: March 2007

Antibodies to the outer surface lipoprotein A (Osp A) of Borrelia burgdorferi confer protection to SCID mice against subsequent tick‐borne or experimental infection. However, Osp A‐specific antibodies are hardly detectable in naturally infected humans, dogs, hamsters and mice. This is most probably due to limited expression of Osp A on spirochetes transmitted from the vector to the host. Here we have tested whether T cell priming of mice would lead to the induction of protective Osp A‐specific antibodies upon infection. It is shown that AKR/N mice, previously immunized with either a single T helper cell peptide of Osp A, or a mixture of 27 peptides spanning the entire molecule, develop Osp A‐specific IgM or IgG antibodies, including those to a prominent protective B cell epitope of Osp A, LA‐2, within 7 days of infection with low doses (103) of culture‐derived spirochetes. In marked contrast, the same groups of pre‐sensitized mice failed to generate any detectable Osp A‐specific antibodies after tick‐borne infection for more than 40 days after infection. All mice, irrespective of their state of T cell immunity to OspA or the mode of infection, produced similar levels of Osp C‐specific IgM and IgG antibodies as early as day 14 after infection. None of the mice previously immunized with Osp A peptides were protected against experimental infection, in spite of the appearance of protective antibodies. It is clear from these data that, in contrast to culture‐derived spirochetes, the naturally transmitted pathogen fails to express Osp A within the mammalian host at levels sufficient for induction of B cell responses, even in the presence of pre‐activated T helper cells. Together with the fact that Osp A‐specific antibodies are mainly operative by eliminating spirochetes from the vector during infestation, the data suggest that Osp A‐vaccination for T helper cell immunity alone is not sufficient to prevent Lyme disease.
Separately expressed T cell receptor α and β chain transgenes exert opposite effects on T cell differentiation and neoplastic transformation
Authors: Brabb Thea , Rubicz Rohina , Mannikko Valerie , Goverman Joan
Published: March 2007

Two aspects of T cell differentiation in T cell receptor (TCR)‐transgenic mice, the generation of an unusual population of CD4−CD8−TCR+ thymocytes and the absence of γδ cells, have been the focus of extensive investigation. To examine the basis for these phenomena, we investigated the effects of separate expression of a transgenic TCR α chain and a transgenic TCR β chain on thymocyte differentiation. Our data indicate that expression of a transgenic TCR α chain causes thymocytes to differentiate into a CD4−CD8−TCR+ lineage at an early developmental stage, depleting the number of thymocytes that differentiate into the αβ lineage. Surprisingly, expression of the TCR α chain transgene is also associated with the development of T cell lymphosarcoma. In contrast, expression of the transgenic TCR β chain causes immature T cells to accelerate differentiation into the αβ lineage and thus inhibits the generation of γδ cells. Our observations provide a model for understanding T cell differentiation in TCR‐transgenic mice.
A T cell receptor (TCR) antagonist competitively inhibits serial TCR triggering by low‐affinity ligands, but does not affect triggering by high‐affinity anti‐CD3 antibodies
Authors: Viola Antonella , Linkert Susanne , Lanzavecchia Antonio
Published: March 2007

It has been demonstrated that modified peptides which fail to induce detectable T cell responses can act as T cell receptor (TCR) antagonists when presented together with agonist by the same antigen‐presenting cell (APC). We report that a TCR antagonist competitively inhibits TCR triggering induced by low‐affinity ligands such as agonistic peptides or bacterial superantigens. However, the same antagonist cannot inhibit TCR triggering and T cell activation induced by high‐affinity anti‐CD3 antibodies that engage most TCR at once. These results indicate that TCR antagonists inhibit T cell responses by interfering with the ongoing process of serial triggering, rather than by delivering an inhibitory signal to T cells.
Trypanosoma cruzi‐infected macrophages are defective in major histocompatibility complex class II antigen presentation
Authors: La Flamme Anne C. , Kahn Stuart J. , Rudensky Alexander Y. , Van Voorhis Wesley C.
Published: March 2007

Trypanosoma cruzi, the intracellular protozoan parasite that causes Chagas' disease, interferes with the host immune response to establish a persistent infection. In this report, we demonstrate that macrophages infected with T. cruzi are unable to effectively present antigens to CD4 T cells. The interference is due to defective antigen‐presenting cell (APC) function, as antigen‐independent stimulation of the T cell in the presence of infected macrophages is not affected. The defect is distal to antigen processing and is not due to decreased major histocompatibility complex (MHC) class II expression, decreased viability, defective peptide loading in the infected macrophages, nor absence of CD28 co‐stimulation. There was a role for gp39:CD40 co‐stimulation during antigen presentation to the T cells we studied, but the expression of CD40 on T. cruzi‐infected macrophages was not decreased. Antigen‐specific adhesion between macrophages and T cells was reduced by infection. Equivalent levels of the adhesion molecules lymphocyte function‐associated antigen‐1, intercellular adhesion molecule‐1, vascular cell adhesion molecule‐1 or very late antigen‐4 are found on infected and uninfected APC, suggesting that reduced expression of these adhesion molecules was not responsible for the defect in antigen‐specific adhesion. The defective T cell:macrophage adhesion may be due to the reduced expression of other adhesion molecules or other changes in the cell induced by infection. Interfering with MHC class II antigen presentation in infected macrophages may help T. cruzi to blunt the immune response by the host.
Fetal and neonatal NK1.1+ Ly‐49− cells can distinguish between major histocompatibility complex class Ihi and class Ilo target cells: Evidence for a Ly‐49‐independent negative signaling receptor
Authors: Sivakumar Pallavur V. , Bennett Michael , Kumar Vinay
Published: March 2007

Natural killer (NK) cell function is regulated by both positive and negative signaling receptors. In adult splenic NK cells, negative signaling has been shown to be mediated by the Ly‐49 family receptors. NK1.1+ 2B4+ CD3− cells that are phenotypically and functionally similar to adult splenic NK cells can be derived from murine fetal liver and thymus. These cells do not express any known Ly‐49 molecules on their surface nor do they contain the known Ly‐49 transcripts. Surface expression of Ly‐49 molecules is first detected on splenic NK1.1+ cells 4–6 days after birth. Despite the absence of these negative signaling receptors, fetal and neonatal Ly‐49− NK cells lyse TAP−/−, major histocompatibility complex (MHC) class Ilo but not TAP+/+, MHC class Ihi target cells. This suggests that fetal and neonatal NK cells express negative signaling receptors other than Ly‐49 molecules.
Polymerase chain reaction‐based identification of a novel serpin from human dendritic cells
Authors: Mueller Chris G. F. , Ho Steve , Massacrier Catherine , Lebecque Serge , Liu Yong‐Jun
Published: March 2007

A subtraction library of CD40‐stimulated human tonsil dendritic cells has been constructed using a polymerase chain reaction approach adapted for low numbers of cells. From this library we identified a cDNA for a serine protease inhibitor, a serpin, which is absent from monocytes, B cells and T cells but expressed in CD40‐activated monocyte‐ and progenitor cell‐generated dendritic cells. In addition, the serpin is expressed in a lung fibroblast cell line and keratinocytes. Its mRNA is detected only in tonsil and thymus. The serpin described here reportedly functions as a megakaryocyte maturation factor in the presence of interleukin (IL)‐3 and IL‐11. This suggests that dendritic cells may promote the immune response by protecting IL‐3 and IL‐11 or other essential proteins from degradation.
Blockade of CD40‐CD40 ligand pathway induces tolerance in murine contact hypersensitivity
Authors: Tang Aimin , Judge Thomas A. , Turka Laurence A.
Published: March 2007

Interactions between CD40 on antigen‐presenting cells and its ligand (CD40L) on T cells has been implicated in T cell‐mediated immune responses. Previously, we have shown that contact hypersensitivity (CHS), a cell‐mediated cutaneous immune response in reaction to haptens, could be subclassified based on whether the hapten primed for Th1 or Th2 cytokines in cells isolated from draining lymph nodes. We also found that tolerance to a Th2‐priming hapten could be induced only by simultane blockade of the CD40‐CD40L and B7‐CD28 at the time of sensitization. Here we demonstrate that blockade of CD40‐CD40L signaling alone induces long‐lasting unresponsiveness to the Th1 hapten 2,4‐dinitrofluorobenzene (DNFB), and inhibits antigen‐specific T cell proliferation in vitro. We find that CD40‐CD40L signaling is required in the sensitization but not elicitation phase of DNFB‐induced CHS, as treatment of mice with anti‐CD40L monoclonal antibody (mAb) does not affect the response to hapten challenge in previously sensitized and untreated animals. Examination of cytokine production shows that anti‐CD40L mAb decreases interferon‐γ production by draining lymph node cells from DNFB‐sensitized mice, and reciprocally increases interleukin (IL)‐4 production. Consistent with this Th1 to Th2 immune deviation, anti‐CD40L mAb prevents the induction of IL‐12 mRNA in regional lymph nodes, an event which is normally seen within 12 h following hapten sensitization. In contrast, suppression of CHS by CTLA4Ig decreased the production of all cytokines by draining lymph node cells. Together, these data show that blockade of the CD40‐CD40L pathway by itself is sufficient to induce tolerance to DNFB‐induced CHS, and that this is associated with blockade of IL‐12 induction and Th1 to Th2 immune deviation.
Anergic T cells effect linked suppression
Authors: Frasca Loredana , Carmichael Paul , Lechler Robert , Lombardi Giovanna
Published: March 2007

Although the phenomenon of T cell‐mediated suppression is well established, particularly in experimental models of transplantation, the mechanisms involved in this form of immunoregulation remain controversial. We have recently demonstrated, using an in vitro system, that anergic T cells can act as suppressor cells by competing for the membrane of the antigen‐presenting cell (APC) and for locally produced interleukin‐2. In the experiments described here we have explored the ability of anergic T cells to effect linked suppression in antigen‐specific and allospecific responses. We observed that anergic antigen‐specific CD4+ T cells can inhibit T cells restricted by a different major histocompatibility complex (MHC) class II molecule provided that both restriction elements are expressed by the same APC. In addition, anergic allospecific clones could also effect linked suppression since they could regulate not only T cells specific for the same alloantigen but also responder T cells with direct allospecificity for a second allogeneic MHC molecule or with indirect, self MHC‐restricted allospecificity for a processed MHC class I alloantigen. Furthermore, the regulatory effect of the anergic T cells was dependent on cell contact, was not dependent upon irradiation, and was maintained during in vitro culture. These data demonstrate that linked suppression can be effected by anergic T cells in vitro. In the clinical context this raises the possibility that induction of tolerance to a single alloantigen could serve to regulate the immune response to an allograft carrying several MHC and minor antigen differences.
CDw78 — a determinant on a major histocompatibility complex class II subpopulation that can be induced to associate with the cytoskeleton
Authors: Rasmussen Anne‐Marie , Hořejši Václav , Levy Finn Olav , Blomhoff Heidi Kiil , Smeland Erlend B. , Beiske Klaus , Michaelsen Terje E. , Gaudernack Gustav , Funderud Steinar
Published: March 2007

In the present study we demonstrate that CDw78 monoclonal antibody (mAb) recognizes a distinct subpopulation of major histocompatibility complex (MHC) class II molecules. We show that the CDw78 epitope is present on less than 10 % of the total number of MHC class II molecules expressed on different cells, is not linked to a single isotype, and exhibits a characteristic expression pattern in tonsils. While mAb against MHC class II (DR, DP and DQ) stained the majority of cells both in the mantle zone and in germinal centers, the CDw78 staining was more heterogeneous with the strongest reactivity and the highest number of positive cells in the mantle zone and in the light centrocyte‐rich part of the germinal centers. Antibodies to this MHC class II subpopulation (e.g. FN1) induced association with the cytoskeleton and a subsequent capping in more than 90 % of peripheral blood B cells. In contrast, mAb against MHC class II (DR, DP and DQ) did not induce association with the cytoskeleton and only 10–20 % of B cells were induced to cap, suggesting that CDw78 defines a population of MHC class II molecules functionally different from the majority of these antigens. Scatchard plot analysis indicates that FN1 mAb is of relatively low affinity (Ka = 1.5 × 108M−1) and monovalent Fab fragments fail to bind to the cell surface with measurable affinity. Our data seen in the context of the ability of FN1 to co‐stimulate B cells with a suboptimal dose of anti‐μ suggest that CDw78 mAb might recognize a functional important subpopulation of MHC class II molecules so far not described. It seems likely that this subpopulation represents dimerized or aggregated MHC class II molecules that can selectively bind this low‐affinity mAb.
Enhanced follicular dendritic cell function in lymph nodes of simian immunodeficiency virus‐infected macaques: Consequences for pathogenesis
Authors: Rosenberg Yvonne J. , Lewis Mark G. , Greenhouse Jack J. , Cafaro Aurelio , Leon Enrique C. , Brown Charles R. , Bieg Kyle E. , Kosco‐Vilbois Marie H.
Published: March 2007

HIV and simian immunodeficiency virus (SIV) infections are characterized by several abnormalities in B cell function. Pathogenesis is also associated with marked changes within germinal centers (GC) including hypertrophy and degeneration of follicular dendritic cells (FDC) and accumulation of both viral antigen and activated CD45RO+CD8+ cells. Since FDC are critical to the generation of antibody‐forming cells and specific B cell memory, the simplest assumption is that such B cell defects directly result from virus‐induced changes in the GC environment. The present study examined FDC‐enriched mesenteric lymph node lymphocyte preparations from early and late stage SIV‐infected and uninfected macaques for their ability to support GC reactions in vitro. The results indicate that FDC function as measured by cluster formation, B cell proliferation and SIV‐specific antibody production is enhanced in SIV‐infected macaques suggesting that, despite FDC atrophy, virus accumulation induces increased FDC‐B cell interactions resulting in B cell hyperactivity. The activation and proliferation of CD8+ cells in FDC‐enriched cultures further suggest that the infiltrating CD8+ population observed in situ in GC of late‐stage SIV/HIV‐infected individuals may also benefit from FDC‐derived growth signals. Thus, in addition to enhanced B cell proliferation and antibody production, hyperactivity of FDC may potentially promote their own self destruction via the infiltrating CD8+ cells. The increased B cell responsiveness may further exacerbate the disease process due to an overall decrease in the affinity of anti‐HIV/SIV antibody, a loss of crucial protective antibodies to other infectious agents and the creation of an environment in which increased trapping of virions facilitates more extensive infection of CD4+ T cells.