PubMed Health⌕ Search

Biomedical subjects

Derry C Roopenian

Publications and source records attributed to Derry C Roopenian.

At least 19 recordsLinked to original sources
PubMed2006

Enhanced half-life of genetically engineered human IgG1 antibodies in a humanized FcRn mouse model: potential application in humorally mediated autoimmune disease.

The MHC class I-like Fc receptor FcRn plays an essential role in extending the half-life (t(1/2)) of IgG antibodies and IgG-Fc-based therapeutics in the circulation. The goal of this study was to analyze the effect of human IgG1 (hIgG1) antibodies with enhanced in vitro binding to FcRn on their in vivo t(1/2) in mice expressing human FcRn (hFcRn). Mutants of the humanized monoclonal Herceptin antibody (Hu4D5-IgG1), directed against human epidermal growth factor receptor 2 (p185 (HER2)), show altered pH-dependent binding to hFcRn in vitro. Two engineered IgG1 mutants (N434A and T307A/E380A/N434A) showed a considerably extended t(1/2) in vivo compared with wild-type antibody in mice expressing an hFcRn transgene (Tg) but not in mice expressing the endogenous mouse FcRn. The efficiency of hFcRn-mediated protection was dependent on hFcRn Tg copy number. Moreover, when injected into FcRn-humanized mice at a concentration sufficient to partially saturate hFcRn, the engineered IgG1 mutants with an extended serum t(1/2) were most effective in reducing the t(1/2) of a tracer hIgG1 antibody. Finally, administration of mutant with high binding to hFcRn ameliorated arthritis induced by passive transfer with human pathogenic plasma. These results indicate that Fc regions modified for high binding affinity to hFcRn increases serum persistence of therapeutic antibodies, that the same approach can be exploited as an anti-autoimmune therapy to promote the clearance of endogenous pathogenic IgG and that FcRn-humanized mice are a promising surrogate for hIgG therapeutic development.

Animals↗
PubMed2006

In vivo role of ER-associated peptidase activity in tailoring peptides for presentation by MHC class Ia and class Ib molecules.

Endoplasmic reticulum (ER)-associated aminopeptidase (ERAP)1 has been implicated in the final proteolytic processing of peptides presented by major histocompatibility complex (MHC) class I molecules. To evaluate the in vivo role of ERAP1, we have generated ERAP1-deficient mice. Cell surface expression of the class Ia molecules H-2Kb and H-2Db and of the class Ib molecule Qa-2 was significantly reduced in these animals. Although cells from mutant animals exhibited reduced capacity to present several self- and foreign antigens to Kb-, Db-, or Qa-1b-restricted CD8+ cytotoxic T cells, presentation of some antigens was unaffected or significantly enhanced. Consistent with these findings, mice generated defective CD8+ T cell responses against class I-presented antigens. These findings reveal an important in vivo role of ER-associated peptidase activity in tailoring peptides for presentation by MHC class Ia and class Ib molecules.

Aminopeptidases↗
PubMed2006

Human antibodies induce arthritis in mice deficient in the low-affinity inhibitory IgG receptor Fc gamma RIIB.

Rheumatoid arthritis (RA) is a complex autoimmune disease with a poorly understood pathogenesis. The disease is associated with polyclonal B cell activation and the production of autoantibodies (autoAbs), but there is a longstanding controversy as to whether such Abs contribute to, or are secondary to, the pathogenesis of RA. To address the potential pathogenicity of human RA-associated Abs, we developed a passive transfer model involving mice deficient in the low-affinity inhibitory Fc receptor, FcgammaRIIB. We report that plasma or serum from patients with active RA can induce inflammation and histological lesions in FcgammaRIIB-/- mice consistent with arthritis, and that this pathogenic activity is caused by the immunoglobulin G-rich fraction. Our results suggest that humoral autoimmunity can contribute directly to autoimmune arthritis, and that FcgammaRIIB-/- mice are a promising model to evaluate the arthritogenic potential of human autoAbs.

Animals↗
PubMed2006

Neonatal Fc receptor for IgG regulates mucosal immune responses to luminal bacteria.

The neonatal Fc receptor for IgG (FcRn) plays a major role in regulating host IgG levels and transporting IgG and associated antigens across polarized epithelial barriers. Selective expression of FcRn in the epithelium is shown here to be associated with secretion of IgG into the lumen that allows for defense against an epithelium-associated pathogen (Citrobacter rodentium). This pathway of host resistance to a bacterial pathogen as mediated by FcRn involves retrieval of bacterial antigens from the lumen and initiation of adaptive immune responses in regional lymphoid structures. Epithelial-associated FcRn, through its ability to secrete and absorb IgG, may thus integrate luminal antigen encounters with systemic immune compartments and as such provide essential host defense and immunoregulatory functions at the mucosal surfaces.

Animals↗
PubMed2005

Generation and characterization of a novel tetravalent anti-CD22 antibody with improved antitumor activity and pharmacokinetics.

The purpose of this study was to prepare a tetravalent anti-human CD22 recombinant antibody with improved antitumor activity and a half life longer than that of its divalent counterpart. We compared the ability of tetravalent vs. divalent antibody to associate/dissociate to/from CD22-positive Daudi cells, to interact with murine and human Fcgamma receptors (FcgammaR), to bind human complement component C1q, to inhibit the growth of tumor cells, to diffuse into various tissues, to be internalized by Daudi cells, to react with human neonatal Fc receptors (FcRn), and to persist in the circulation of normal mice. As compared to the murine or chimeric divalent antibodies, the chimeric tetravalent counterpart has a longer half life in mice. It also has an affinity for FcRns that is identical to that of human IgG. The tetravalent antibody has increased antitumor activity in vitro and completely conserved effector functions (binding to FcgammaR-positive cells and to C1q) in vitro. Despite its 33% higher molecular weight, it penetrates mouse tissues as well as its divalent antibody counterpart. Based on the improved in vitro performance and pharmacokinetics of the tetravalent antibody it will now be tested for its antitumor activity in vivo.

Animals↗
PubMed2005

Complete FcRn dependence for intravenous Ig therapy in autoimmune skin blistering diseases.

Numerous mechanisms of action have been proposed for intravenous Ig (IVIG). In this study, we used IgG passive transfer murine models of bullous pemphigoid (BP), pemphigus foliaceus (PF), and pemphigus vulgaris (PV) to test the hypothesis that the effect of IVIG in autoantibody-mediated cutaneous bullous diseases is to accelerate the degradation of pathogenic IgG by saturation of the MHC-like Fc receptor neonatal Fc receptor (FcRn). BP, PF, and PV are organ-specific antibody-mediated diseases in which autoantibodies target the hemidesmosomal antigen BP180 and desmosomal antigens Dsg1 and Dsg3, respectively. Antibodies against BP180, Dsg1, and Dsg3, when injected into neonatal mice, induce the BP, PF, and PV disease phenotypes, respectively. We found that FcRn-deficient mice were resistant to experimental BP, PF, and PV. Circulating levels of pathogenic IgG in FcRn-deficient mice were significantly reduced compared with those in WT mice. Administration of high-dose human IgG (HDIG) to WT mice also drastically reduced circulating pathogenic IgG levels and prevented blistering. In FcRn-deficient mice, no additional protective effect with HDIG was realized. These data demonstrate that the therapeutic efficacy of HDIG treatment in the pemphigus and pemphigoid models is dependent on FcRn. Thus, FcRn is a promising therapeutic target for treating such IgG-mediated autoimmune diseases.

Animals↗
PubMed2005

Albumin turnover: FcRn-mediated recycling saves as much albumin from degradation as the liver produces.

It is now understood that the nonclassical major histocompatibility complex-I molecule FcRn binds albumin and retrieves it from an intracellular degradative fate. Whether FcRn in the liver modulates albumin turnover through effects on biosynthesis and production is not known. Thus we quantified the appearance of biosynthetically labeled albumin in plasma after an intravenous bolus injection of [(3)H]leucine in FcRn-deficient mice. The production rates for both albumin (FcRn substrate) and transferrin (nonsubstrate) are increased by approximately 20% in FcRn-deficient mice compared with normal mice, likely compensating for the lowered plasma oncotic pressure caused by hypoalbuminemia in FcRn-deficient mice. Determining the magnitude of FcRn-mediated effects on albumin turnover, we then measured the steady-state plasma concentrations of biosynthetically labeled albumin and transferrin during [(3)H]leucine infusion. The concentration of albumin was approximately 40% lower in FcRn-deficient mice compared with normal mice. Furthermore, the approximately 40% lower plasma albumin concentration in FcRn-deficient mice along with the approximately 20% increase in albumin production indicate, by the mass-balance equation, that albumin degradation in FcRn-deficient mice is twice that of normal mice. These studies of biosynthetically labeled, and thus native, albumin support our previous finding that FcRn protects albumin from degradation. Permitting quantification of the magnitude of FcRn-mediated recycling, they further indicate that FcRn has extraordinary capacity: the amount of albumin saved from degradation by FcRn-mediated recycling is the same as that produced by the liver.

Albumins↗
PubMed2005

Searching QTL by gene expression: analysis of diabesity.

BACKGROUND: Recent developments in sequence databases provide the opportunity to relate the expression pattern of genes to their genomic position, thus creating a transcriptome map. Quantitative trait loci (QTL) are phenotypically-defined chromosomal regions that contribute to allelically variant biological traits, and by overlaying QTL on the transcriptome, the search for candidate genes becomes extremely focused. RESULTS: We used our novel data mining tool, ExQuest, to select genes within known diabesity QTL showing enriched expression in primary diabesity affected tissues. We then quantified transcripts in adipose, pancreas, and liver tissue from Tally Ho mice, a multigenic model for Type II diabetes (T2D), and from diabesity-resistant C57BL/6J controls. Analysis of the resulting quantitative PCR data using the Global Pattern Recognition analytical algorithm identified a number of genes whose expression is altered, and thus are novel candidates for diabesity QTL and/or pathways associated with diabesity. CONCLUSION: Transcription-based data mining of genes in QTL-limited intervals followed by efficient quantitative PCR methods is an effective strategy for identifying genes that may contribute to complex pathophysiological processes.

Algorithms↗
PubMed2005

Accelerated wound healing of alkali-burned corneas in MRL mice is associated with a reduced inflammatory signature.

PURPOSE: The present study was conducted to investigate healing of alkali-burned corneas in MRL/MpJ (MRL) mice. METHODS: Gross, clinical, and histologic criteria were used to compare healing of alkali-burned corneas in MRL and control C57BL/6J (B6) mice. Effects of neutrophil depletion of B6 mice and allogeneic reconstitution of B6 mice with MRL bone marrow on wound healing were evaluated. Gene expression patterns in normal and wounded corneas were surveyed with array-based quantitative real-time RT-PCR (AQPCR). RESULTS: MRL mice showed accelerated reepithelialization and decreased corneal opacity compared with B6 mice after alkali wounding. Marked inflammatory cell infiltration and fibrosis were evident in the corneas and anterior chambers of B6 mice. MRL mice showed less severe lesions, except for stromal edema. Rapid reepithelialization and reduced keratitis/iritis were also observed in neutrophil-depleted B6 mice, but not in B6 mice reconstituted with MRL bone marrow. AQPCR showed transcriptional changes of fewer genes associated with inflammation and corneal tissue homeostasis in alkali-burned corneas from MRL mice. Increased expression of an anti-inflammatory gene, Socs1, and a gene associated with healing, Mmp1a, were evident in MRL corneas. CONCLUSIONS: Alkali-burned corneas heal faster and more completely in MRL mice than in B6 mice, by means of rapid reepithelialization, reduced inflammation, and reduced fibrosis. Reduced inflammation, including decreased neutrophil infiltrates and the lack of a robust proinflammatory gene expression signature correlates with the rapid healing. However, the rapid-healing phenotype is not intrinsic to MRL hematopoietic progenitor cells.

Animals↗
PubMed2004

Evidence for selective transformation of autoreactive immature plasma cells in mice deficient in Fasl.

Germline mutations in Fas and Fasl induce nonmalignant T cell hyperplasia and systemic autoimmunity and also greatly increase the risk of B cell neoplasms. B lymphomas occurring in Fasl mutant (gld) mice usually are immunoglobulin (Ig) isotype switched, secrete Ig, and are plasmacytoid in appearance but lack Myc translocations characteristic of other plasma cell (PC) neoplasms. Here, we explore the relationship between B cell autoreactivity and transformation and use gene expression profiling to further classify gld plasmacytoid lymphomas (PLs) and to identify genes of potential importance in transformation. We found that the majority of PLs derive from antigen-experienced autoreactive B cells producing antinuclear antibody or rheumatoid factor and exhibit the skewed Ig V gene repertoire and Ig gene rearrangement patterns associated with these specificities. Gene expression profiling revealed that both primary and transplanted PLs share a transcriptional profile that places them at an early stage in PC differentiation and distinguishes them from other B cell neoplasms. In addition, genes were identified whose altered expression might be relevant in lymphomagenesis. Our findings provide a strong case for targeted transformation of autoreactive B cells in gld mice and establish a valuable model for understanding the relationship between systemic autoimmunity and B cell neoplasia.

Animals↗
PubMed2004

Regulation of B cell differentiation and plasma cell generation by IL-21, a novel inducer of Blimp-1 and Bcl-6.

IL-21 is a type I cytokine whose receptor is expressed on T, B, and NK cells. Within the B cell lineage, IL-21 regulates IgG1 production and cooperates with IL-4 for the production of multiple Ab classes in vivo. Using IL-21-transgenic mice and hydrodynamics-based gene delivery of IL-21 plasmid DNA into wild-type mice as well as in vitro studies, we demonstrate that although IL-21 induces death of resting B cells, it promotes differentiation of B cells into postswitch and plasma cells. Thus, IL-21 differentially influences B cell fate depending on the signaling context, explaining how IL-21 can be proapoptotic for B cells in vitro yet critical for Ag-specific Ig production in vivo. Moreover, we demonstrate that IL-21 unexpectedly induces expression of both Blimp-1 and Bcl-6, indicating mechanisms as to how IL-21 can serve as a complex regulator of B cell maturation and terminal differentiation. Finally, BXSB-Yaa mice, which develop a systemic lupus erythematosus-like disease, have greatly elevated IL-21, suggesting a role for IL-21 in the development of autoimmune disease.

Animals↗
PubMed2004

Duration of alloantigen presentation and avidity of T cell antigen recognition correlate with immunodominance of CTL response to minor histocompatibility antigens.

CD8 T lymphocytes (CTL) responsive to immunodominant minor histocompatibility (minor H) Ags are thought to play a disproportionate role in allograft rejection in MHC-identical solid and bone marrow transplant settings. Although many studies have addressed the mechanisms underlying immunodominance in models of infectious diseases, cancer immunotherapy, and allograft immunity, key issues regarding the molecular basis of immunodominance remain poorly understood. In this study, we exploit the minor H Ag system to understand the relationship of the various biochemical parameters of Ag presentation and recognition to immunodominance. We show that the duration of individual minor H Ag presentation and the avidity of T cell Ag recognition influence the magnitude and, hence, the immunodominance of the CTL response to minor H Ags. These properties of CTL Ag presentation and recognition that contribute to immunodominance have implications not only for tissue transplantation, but also for autoimmunity and tumor vaccine design.

Animals↗
PubMed2004

Human neonatal Fc receptor mediates transport of IgG into luminal secretions for delivery of antigens to mucosal dendritic cells.

Mucosal secretions of the human gastrointestinal, respiratory, and genital tracts contain significant quantities of IgG. The mechanism by which IgG reaches luminal secretions and the function of IgG in these locations are unknown. Here, we find that the human neonatal Fc receptor (FcRn) is the vehicle that transports IgG across the intestinal epithelial barrier into the lumen where the IgG can bind cognate antigen. The FcRn can then recycle the IgG/antigen complex back across the intestinal barrier into the lamina propria for processing by dendritic cells and presentation to CD4(+) T cells in regional organized lymphoid structures. These results explain how IgG is secreted onto mucosal surfaces and scavenges luminal antigens for recognition by the immune system.

Adoptive Transfer↗
PubMed2004

ExQuest, a novel method for displaying quantitative gene expression from ESTs.

There is a pressing need for interactive bioinformatics tools that empower investigators with the means to extract information and organize it in a simplified but meaningful format. A wealth of mammalian gene expression data is readily accessible, much of which is based on expressed sequence tags (ESTs). Many mammalian ESTs are derived from tissue-specific cDNA libraries in which the number of ESTs representing a specific gene approximates the transcriptional expression level in the source tissue. Our program ExQuest (Expressional Quantification of ESTs) organizes the public EST database (dbEST) into hierarchical tissue classes and reports tissue or developmental gene expression patterns for both mRNA and genomic sequences. ExQuest also displays tissue expression patterns of genes in the context of assembled chromosomes. These interactive "transcriptome" maps provide a novel tool for investigating the genomic basis of gene expression as well as prioritizing candidate genes within genetically mapped mutant and quantitative trait loci.

Animals↗
PubMed2003

Another view of T cell antigen recognition: cooperative engagement of glycolipid antigens by Va14Ja18 natural T(iNKT) cell receptor [corrected].

Va14Ja18 natural T (iNKT) cells rapidly elicit a robust effector response to different glycolipid Ags, with distinct functional outcomes. Biochemical parameters controlling iNKT cell function are partly defined. However, the impact of iNKT cell receptor beta-chain repertoire and how alpha-galactosylceramide (alpha-GalCer) analogues induce distinct functional responses have remained elusive. Using altered glycolipid ligands, we discovered that the Vb repertoire of iNKT cells impacts recognition and Ag avidity, and that stimulation with suboptimal avidity Ag results in preferential expansion of high-affinity iNKT cells. iNKT cell proliferation and cytokine secretion, which correlate with iNKT cell receptor down-regulation, are induced within narrow biochemical thresholds. Multimers of CD1d1-alphaGalCer- and alphaGalCer analogue-loaded complexes demonstrate cooperative engagement of the Va14Ja18 iNKT cell receptor whose structure and/or organization appear distinct from conventional alphabeta TCR. Our findings demonstrate that iNKT cell functions are controlled by affinity thresholds for glycolipid Ags and reveal a novel property of their Ag receptor apparatus that may have an important role in iNKT cell activation.

Animals↗
PubMed2003

A single nucleotide polymorphism in the Emp3 gene defines the H4 minor histocompatibility antigen.

Minor histocompatibility antigens (minor H antigen) elicit strong T-cell-mediated responses during both graft rejection and graft versus leukemia (GvL) among MHC-matched individuals (where MHC is major histocompatibility complex). Employing expression-cloning methodology, we have identified a cDNA clone, MI-35, encoding the immunodominant H4b minor H antigen within the classical mouse H4 complex. The minimal antigenic epitope derived from H4b presented on Kb class I MHC is SGIVYIHL (SYL8) and the polymorphism is due to C-->T nucleotide modification in p3 resulting in the change of threonine (ACT) to isoleucine (ATT). The results presented here demonstrate that amino acid variation in the allelic epitopes results in the low abundance of H4a peptide. The differential peptide copy number resulted in an immunodominant cytotoxic T cells (CTL) response directed against H4b while the anti-B6 response directed against H4a was easily dominated. These results provide a molecular mechanism for the H4 minor H antigen and suggest a novel mechanism by which alloantigenic disparity caused by conservative amino acid changes can be augmented by posttranslational antigen processing events.

Amino Acid Sequence↗
PubMed2003

The H4b minor histocompatibility antigen is caused by a combination of genetically determined and posttranslational modifications.

Minor histocompatibility (H) Ag disparities result in graft-vs-host disease and chronic solid allograft rejection in MHC-identical donor-recipient combinations. Minor H Ags are self protein-derived peptides presented by MHC class I molecules. Most arise as a consequence of allelic variation in the bound peptide (p) that results in TCR recognizing the p/MHC as foreign. We used a combinational peptide screening approach to identify the immune dominant H2K(b)-restricted epitope defining the mouse H4(b) minor H Ag. H4(b) is a consequence of a P3 threonine to isoleucine change in the MHC-bound peptide derived from epithelial membrane protein-3. This allelic variation also leads to phosphorylation of the H4(b) but not the H4(a) epitope. Further, ex vivo CD8(+) T lymphocytes bind phosphorylated Ag tetramers with high efficiency. Although we document the above process in the minor H Ag system, posttranslational modifications made possible by subtle amino acid changes could also contribute to immunogenicity and immune dominance in tumor immunotherapeutic settings.

Amino Acid Substitution↗