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Effector Mechanisms (effector + mechanism)
Selected AbstractsCross-linking tumor cells with effector cells via CD55 with a bispecific mAb induces ,-glucan-dependent CR3-dependent cellular cytotoxicityEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 4 2006Abstract Complement (C) regulatory proteins decrease the effectiveness of immunotherapeutic anti-cancer antibodies. Bispecific mAb (bi-mAb) that target a tumor antigen and simultaneously inhibit a C regulator increase the effectiveness of such a therapy. Here we investigated the mechanism by which bi-mAb increase tumor cell lysis. Apart from C-dependent cytotoxicity, C activation can lead to complement receptor 3 (CR3)-dependent cellular cytotoxicity (CR3-DCC) by CR3-positive effector cells in the presence of ,-glucan. Here we show that an anti-Ep-CAM*anti-CD55 bi-mAb induced more than threefold higher CR3-DCC (71%) of human colorectal cancer cells compared with anti-Ep-CAM alone (20%). This CR3-DCC was dependent on the binding of the anti-CD55 arm of tumor-bound anti-Ep-CAM*anti-CD55 bi-mAb to effector cell CD55, CR3 priming by ,-glucan and the presence of iC3b on the target cell. Comparable lysis could be obtained in the absence of iC3b, when CR3 and CD55 were cross-linked on the effector cells, suggesting cooperation between CD55 and CR3 in signal transduction. Tumor cells with low antigen expression were effectively lysed via this mechanism in contrast to direct C-dependent cytotoxicity. These data imply that the effectiveness of mAb immunotherapy can be improved using anti-tumor antigen*anti-CD55 bi-mAb and ,-glucan, thereby initiating CR3-DCC as an additional effector mechanism that is efficient for eradication of tumor cells with lower antigen expression. [source] Astrocyte-specific expression of a soluble form of the murine complement control protein Crry confers demyelination protection in the cuprizone modelGLIA, Issue 14 2007Dustin T. Briggs Abstract Complement has been implicated as a potential effector mechanism in neurodegeneration; yet the precise role of complement in this process remains elusive. In this report, we have utilized the cuprizone model of demyelination-remyelination to examine the contribution of complement to disease. C1q deposition was observed in the corpus callosum of C57BL/6 mice during demyelination, suggesting complement activation by apoptotic oligodendrocyte debris. Simultaneously, these mice lost expression of the rodent complement regulatory protein, Crry. A soluble CNS-specific form of the Crry protein (sCrry) expressed in a transgenic mouse under the control of an astrocyte-specific promoter was induced in the corpus callosum during cuprizone treatment. Expression of this protein completely protected the mice from demyelination. Interestingly, sCrry mice had low levels of demyelination at later times when control mice were remyelinating. Although the sCrry transgenic mice had lower levels of demyelination, there was no decrease in overall cellularity, however there were decreased numbers of microglia in the sCrry mice relative to controls. Strikingly, sCrry mice had early recovery of mature oligodendrocytes, although they later disappeared. TUNEL staining suggested that production of the sCrry protein in the transgenic mice protected from a late apoptosis event at 3 weeks of cuprizone treatment. Our data suggest complement provides some protection of mature oligodendrocytes during cuprizone treatment but may be critical for subsequent remyelination events. These data suggest that temporal restriction of complement inhibition may be required in some disease settings. © 2007 Wiley-Liss, Inc. [source] Design and engineering human forms of monoclonal antibodiesDRUG DEVELOPMENT RESEARCH, Issue 3 2004Manuel L. Penichet Abstract The antibody molecule has multiple properties that make it a key component of the immune response. These include its ability to recognize a vast array of different foreign substrates and to interact with and activate the host effector systems. Antibodies with defined specificities may serve as "magic bullets" for the diagnosis and therapy of multiple diseases. With the development of the hybridoma technology, it was possible to produce rodent (mouse or rat) monoclonal antibodies that are the product of a single clone of antibody producing cells and have only one antigen binding specificity. However, the therapeutic use of rodent monoclonals antibodies in humans is limited by their immunogenicity, short circulating half-life, and inability to efficiently trigger human effector mechanisms. However, it proved difficult to produce human monoclonal antibodies using the same methods. To address these problems genetic engineering and expression systems have instead been used to produce chimeric, humanized, and totally human antibodies as well as antibodies with novel structures and functional properties. In addition, the use of yeast and human artificial chromosome vectors for animal transgenesis has allowed the development of animal models that produce antigen specific antibodies that are totally human. As a consequence, recombinant antibody-based therapies are now used to treat a variety of clinical conditions including infectious diseases, inflammatory disorders, and cancer. This article summarizes and compares different strategies for designing and engineering human antibodies and their derivatives. Drug Dev. Res. 61:121,136, 2004. © 2004 Wiley-Liss, Inc. [source] Nramp1 -functionality increases iNOS expression via repression of IL-10 formationEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 11 2008Gernot Fritsche Abstract In mice, resistance to certain intracellular microbes depends on the expression of a late phagosomal protein termed natural-resistance associated macrophage protein 1 (Nramp1, Slc11a1). Nramp1- functionality is associated with alterations of cellular iron homeostasis and a sustained pro-inflammatory immune response, including the formation of the antimicrobial effector molecule NO. To investigate the underlying mechanism we used RAW-264.7 murine macrophage cells stably transfected with a functional Nramp1 allele (RAW-37) or Nramp1 non-functional controls (RAW-21). We found that the production of and signalling by the anti-inflammatory cytokine IL-10 was significantly enhanced in macrophages lacking functional Nramp1. Upon infection of macrophages with Salmonella typhimurium pathogen survival was significantly better in RAW-21 than in RAW-37, which inversely correlated to NO and TNF-, formation. Addition of a neutralising anti-IL-10 antibody to RAW-21 cells led to a significantly reduced survival of S. typhimurium within these cells and enhanced formation of NO and TNF-, reaching levels comparable to that observed in cells bearing functional Nramp1. Oppositely, supplementation of iron to RAW-21 cells further increased IL-10 formation. Thus, Nramp1 mediates effective host defence in part via suppression of excessive IL-10 production which may relate to Nramp1- mediated reduction of cellular iron pools, thus strengthening antimicrobial effector mechanisms. [source] Fas and TNFR1, but not cytolytic granule-dependent mechanisms, mediate clearance of murine liver adenoviral infection,HEPATOLOGY, Issue 1 2005Marwan S. Abougergi After intravenous injection of replication-deficient adenovirus, hepatocytes are transduced and express high levels of adenovirus-encoded genes. However, adenovirally encoded gene expression is ablated rapidly by CD8+ T-cell,dependent mechanisms. Thus, this model is suitable for examining intrahepatic cytotoxic T lymphocyte (CTL) effector mechanisms. In the present studies, recombinant adenoviruses encoding secreted (human apolipoprotein A-I) or intracellular (,-galactosidase) gene products were infused into mice with genetic deficiencies affecting the granule exocytosis-, Fas-, or tumor necrosis factor receptor 1 (TNFR1)-mediated pathways of CTL and natural killer cell effector function; the rates of clearance of adenovirus-encoded gene products were assessed. Clearance of secreted or intracellular adenoviral gene products was not delayed in perforin-deficient mice or dipeptidyl peptidase I-deficient mice, which fail to process and activate granzyme A or granzyme B. TNFR1-deficient mice also exhibited no delay in clearance of adenoviral gene products. However, adenoviral clearance from Fas-deficient mice was delayed, and such delays were much greater in mice deficient in both TNFR1 and Fas. In contrast, chimeric mice lacking both hepatic Fas and lymphocyte perforin function exhibited no greater delay in adenoviral clearance than chimeras deficient only in hepatic Fas expression. In conclusion, Fas-dependent mechanisms are required for efficient clearance of virally infected hepatocytes and, in Fas-deficient animals, TNFR1-dependent mechanisms provide an alternative mechanism for hepatic adenovirus clearance. In contrast, perforin- and granule protease,dependent cytotoxicity mechanisms play no apparent role in clearance of adenovirus from the liver. (HEPATOLOGY 2005;41:97,105.) [source] Androgen insensitivity and male infertility,INTERNATIONAL JOURNAL OF ANDROLOGY, Issue 1 2003O. Hiort Summary Abnormal human spermatogenesis can be caused by defects in androgen action because of androgen insensitivity. A variety of mutations have been described in the human androgen receptor gene associated with male infertility. These can be attributed to two molecular mechanisms. First, point mutations in the androgen receptor gene cause alterations in the amino acid sequence and, hence, lead to apparently slight changes in the androgen receptor effector mechanisms and mild androgen insensitivity. Secondly, variations in the polymorphic poly glutamine segment within the N-terminal end of the androgen receptor have been ascribed to correlate with fertility aspects possibly because of modifications of transcriptional regulatory mechanisms. It has been postulated that longer poly glutamine segments are associated with decreased sperm counts. However, the molecular mechanisms that lead to inhibition of spermatogenesis because of a mutated androgen receptor are poorly understood and will need more focus in the future. [source] Evaluation of the immune response against Strongyloides venezuelensis in antigen-immunized or previously infected micePARASITE IMMUNOLOGY, Issue 3 2008A. FERNANDES Summary The present study was carried out to investigate the immune response against Strongyloides venezuelensis infection in Balb/c mice previously immunized with larva-antigens or primed with live-larvae. Our results indicate that all primed mice developed a strong protection against challenge infection that remained active for 45 days. In mice primed with live-larvae the challenge infection resulted in great reduction of migrating larvae and the worms were completely eliminated from the small intestine before maturation. The protection pattern did not alter when the primary infection was aborted by drug treatment. In these experimental groups, the challenge infection was accompanied by a type-2 predominant immune response, intense IgE and reactive IgG1 production, and granulocyte infiltration in skin, lungs and intestine. The challenge infection in antigen-immunized mice also resulted in great reduction of migrating larvae. However, the worms that reached the host intestine matured, produced eggs and were eliminated similarly to the ones from nonimmunized mice. Protective mechanisms after immunization with larva antigen were migrating larva-specific and associated with a strong and mixed Th1 and Th2 response, without tissue granulocyte infiltration. In conclusion, protective immunity induced by a previous infection or antigen-immunization are stage-specific and operate through different effector mechanisms. [source] CD154 Deficiency Uncouples Allograft CD8+ T-Cell Effector Function from Proliferation and Inhibits Murine Airway ObliterationAMERICAN JOURNAL OF TRANSPLANTATION, Issue 12 2009P. D. Shah Obliterative bronchiolitis (OB) limits the long-term success of lung transplantation, while T-cell effector mechanisms in this process remain incompletely understood. Using the murine heterotopic tracheal transplant model of obliterative airway disease (OAD) to characterize airway allograft rejection, we previously reported an important role for CD8+ T cells in OAD. Herein, we studied the role of CD154/CD40 costimulation in the regulation of allospecific CD8+ T cells, as airway rejection has been reported to be CD154-dependent. Airway allografts from CD154,/, recipients had significantly lower day 28 OAD scores compared to wild-type (WT) recipients, and adoptive transfer of CD8+ T cells from WT recipients, but not CD154,/, recipients, were capable of airway rejection in fresh CD154,/, allograft recipients. Intragraft CD8+ T cells from CD154,/, mice showed similar expression of the surface markers CD69, CD62Llow CD44high and PD-1, but markedly impaired IFN-, and TNF-, secretion and granzyme B expression versus WT controls. Unexpectedly, intragraft and systemic CD8+ T cells from CD154,/, recipients demonstrated robust in vivo expansion similar to WT recipients, consistent with an uncoupling of proliferation from effector function. Together, these data suggest that a lack of CD154/CD40 costimulation results in ineffective allospecific priming of CD8+ T cells required for murine OAD. [source] Delineating the impact of neuroantigen vs genetic diversity on MP4-induced EAE of C57BL/6 and B6.129 miceAPMIS, Issue 12 2009STEFANIE KUERTEN MBP-PLP fusion protein (MP4)-induced experimental autoimmune encephalomyelitis (EAE) is a model for multiple sclerosis (MS) that encompasses both a time-dependent attack on central nervous system (CNS) regions and a B cell component, mirroring important features of human multiple sclerosis. Comparing C57BL/6 with B6.129 mice immunized with MP4, we point out similarities regarding these hallmarks and thus propose that they are largely dependent on the nature of the MP4 antigen itself, while differences between the two strains suggest that additional fine-tuning is brought about by the genetic repertoire of the animal. Overall, our data imply that (i) the interplay between both the antigenic trigger and genetic variables can define the outcome of MP4-induced autoimmune encephalomyelitis in C57BL/6 and B6.129 mice and (ii) that MP4 is not only a strong neuroantigen when it comes to reproducing the dynamics in effector mechanisms as is typical of the disease but also a promising agent for studying interindividual heterogeneity derived from genetic diversity in EAE/MS. [source] Glycan profiling of anti,citrullinated protein antibodies isolated from human serum and synovial fluidARTHRITIS & RHEUMATISM, Issue 6 2010Hans U. Scherer Objective Anti,citrullinated protein antibodies (ACPA) exhibit unique specificity for rheumatoid arthritis. However, it is incompletely understood whether and how ACPA contribute to disease pathogenesis. The Fc part of human IgG carries 2 N-linked glycan moieties that are crucial for the structural stability of the antibody and that modulate both its binding affinity to Fc, receptors and its ability to activate complement. We undertook this study to analyze Fc glycosylation of IgG1 ACPA in serum and synovial fluid (SF) in order to further characterize the immune response to citrullinated antigens. Methods ACPA were isolated by affinity purification using cyclic citrullinated peptides as antigen. IgG1 Fc glycosylation was analyzed by mass spectrometry. ACPA IgG1 glycan profiles were compared with glycan profiles of total serum IgG1 obtained from 85 well-characterized patients. Glycan profiles of paired SF and serum samples were available from 11 additional patients. Results Compared with the pool of serum IgG1, ACPA IgG1 lacked terminal sialic acid residues. In SF, ACPA were highly agalactosylated and lacked sialic acid residues, a feature that was not detected for total SF IgG1. Moreover, differential ACPA glycan profiles were detected in rheumatoid factor (RF),positive and RF-negative patients. Conclusion ACPA IgG1 exhibit a specific Fc-linked glycan profile that is distinct from that of total serum IgG1. Moreover, Fc glycosylation of ACPA differs markedly between SF and serum. Since Fc glycosylation directly affects the recruitment of Fc-mediated effector mechanisms, these data could further our understanding of the contribution of ACPA to disease pathogenesis. [source] Anti,cyclic citrullinated peptide antibodies from rheumatoid arthritis patients activate complement via both the classical and alternative pathwaysARTHRITIS & RHEUMATISM, Issue 7 2009L. A. Trouw Objective It has been suggested that anti,citrullinated protein antibodies (ACPAs) play an important role in the pathogenesis of rheumatoid arthritis (RA). To exert their pathologic effects, ACPAs must recruit immune effector mechanisms such as activation of the complement system. Mouse models of RA have shown that, surprisingly, arthritogenic antibodies activate the alternative pathway of complement rather than the expected classical pathway. This study was undertaken to investigate whether human anti,cyclic citrullinated peptide (anti-CCP) antibodies activate the complement system in vitro and, if so, which pathways of complement activation are used. Methods We set up novel assays to analyze complement activation by anti-CCP antibodies, using cyclic citrullinated peptide,coated plates, specific buffers, and normal and complement-deficient sera as a source of complement. Results Anti-CCP antibodies activated complement in a dose-dependent manner via the classical pathway of complement, and, surprisingly, via the alternative pathway of complement. The lectin pathway was not activated by anti-CCP antibodies. Complement activation proceeded in vitro up to the formation of the membrane attack complex, indicating that all activation steps, including the release of C5a, took place. Conclusion Our findings indicate that anti-CCP antibodies activate the complement system in vitro via the classical and alternative pathways but not via the lectin pathway. These findings are relevant for the design of interventions aimed at inhibition of complement-mediated damage in RA. [source] Allergic diseases and asthma in relation to serum immunoglobulins and salivary immunoglobulin A in pre-school children: a follow-up community-based studyCLINICAL & EXPERIMENTAL ALLERGY, Issue 1 2005B. R. Lúðvíksson Summary Background We have previously reported an association between low IgA and allergic manifestations in early childhood (0,2 years) and have now followed our cohort for an additional 2 years. Objective To evaluate in a longitudinal community-based cohort study the association between maturation of Ig production and allergic manifestations in the first 4 years of life. Methods A cohort of 161 randomly selected children was followed from birth to the age of 42,48 months and evaluated at 18,23 months (EV1; n=179) and again at the age of 42,48 months (EV2; n=161). Diagnoses were made with the help of a clinical questionnaire, physical examination and skin prick tests (SPTs) to 10 common allergens. Serum immunoglobulins were measured at EV1 and EV2, and salivary IgA (sal-IgA) at EV2. Results Serum IgA, IgE, IgG1, IgG2 and IgG4 increased from 2 to 4 years of age (P<0.001) and their levels showed close correlations (P0.01 for most comparisons). Children with one or more positive SPTs had lower serum IgA (P=0.004) and IgG4 (P=0.05) at EV2 than those who did not respond, and children who developed allergic rhinitis between EV1 and EV2 had low sal-IgA (P=0.006) and IgG3 (P<0.05) at EV2. Atopic eczema was associated with low sal-IgA at EV2, and children who developed eczema between EV1 and EV2 had significantly lower sal-IgA than those who recovered after EV1 (P=0.02). Conclusion Allergic manifestations in predisposed children may be influenced by the rate of maturation of immunological components that counteract sensitization or inhibit effector mechanisms of allergy. [source] Traditional therapies: glucocorticoids, azathioprine, methotrexate, hydroxyureaCLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 7 2002G. Belgi Summary The ,old favourites' used for treatment of inflammatory diseases, and hence, the original immunomodulators, include the glucocorticoids, azathioprine, methotrexate and hydroxyurea. Glucocorticoids are still one of the most effective anti-inflammatory agents because they work on several different intracellular processes and hence, block many components that contribute to inflammatory and immune responses. They bind to intracellular glucocorticoid receptors which transport them into the nucleus. Here the receptor/steroid complex may bind to many genes that interact with transcription factors including NF,B and AP-1, to inhibit their activation, thereby preventing activation of many genes encoding immune effector and pro-inflammatory cytokines. Also, protein kinases involved in intracellular signalling, are directly activated resulting in phosphorylation of various targets of which Annexin (AXA)-1 is critical in inhibiting biosynthesis of both purines and DNA. This results in reduced proliferation of B and T lymphocytes, reduced immune effector mechanisms and reduced recruitment of mononuclear cells including monocytes into sites of immune inflammation. Methotrexate also blocks DNA synthesis and hence cellular proliferation but also induces release of adenosine. This inhibits chemotaxis of polymorph neutrophils and release of critical cytokines such as TNF-, and Interleukins 6 and 8. Hydroxyurea also inhibits DNA synthesis with inhibitory effects on proliferation of lymphocytes and possibly kerationcytes. Even though many new agents with much greater selectivity are coming through into clinical use, this group of old agents still have an absolutely central position in the therapeutic armamentarium. Their value lies in the fact that they are not ,clean' drugs with narrow effects but they inhibit a wide range of mechanisms involved in immune and inflammatory processes. [source] Glomerulonephritis, Th1 and Th2: what's new?CLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 2 2005P. G. Tipping Summary Glomerulonephritis (GN), the major worldwide cause of chronic renal disease and renal failure, shows a wide spectrum of histological patterns, severity of injury and clinical outcomes that may be related to the nature of the nephritogenic immune response. In the majority of cases, there is evidence of a central role for cognate immunity in the initiation of human GN and contributions of both humoral and cellular effector mechanisms have been demonstrated in both humans and in animal models. T helper cell subsets are known to activate different immune effector mechanisms which influence disease outcomes in infectious and autoimmune diseases and evidence is now accumulating that Th1 and Th2 subsets direct diverging effector pathways that lead to different patterns and severity of glomerular injury in GN. Th1-predominant responses appear to be associated strongly with proliferative and crescentic forms of GN that result in severe renal injury, while Th2 responses are associated with membranous patterns of injury. The challenge remains to understand fully the relevance of T helper cell subset responses to the spectrum of human GN and to apply this new knowledge to the development of more potent and selective therapeutic strategies. [source] IDENTIFYING COEVOLUTIONARY PATTERNS IN HUMAN LEUKOCYTE ANTIGEN (HLA) MOLECULESEVOLUTION, Issue 5 2010Xiaowei Jiang The antigenic peptide, major histocompatibility complex molecule (MHC; also called human leukocyte antigen, HLA), coreceptor CD8, or CD4 and T-cell receptor (TCR) function as a complex to initiate effectors' mechanisms of the immune system. The tight functional and physical interaction among these molecules may have involved strong coevolution links among domains within and between proteins. Despite the importance of unraveling such dependencies to understand the arms race of host,pathogen interaction, no previous studies have aimed at achieving such an objective. Here, we perform an exhaustive coevolution analysis and show that indeed such dependencies are strongly shaping the evolution and probably the function of these molecules. We identify intramolecular coevolution in HLA class I and II at domains important for their immune activity. Most of the amino acid sites identified to be coevolving in HLAI have been also detected to undergo positive Darwinian selection highlighting therefore their adaptive value. We also identify coevolution among antigen-binding pockets (P1-P9) and among these and TCR-binding sites. Conversely to HLAI, coevolution is weaker in HLAII. Our results support that such coevolutionary patterns are due to selective pressures of host,pathogen coevolution and cooperative binding of TCRs, antigenic peptides, and CD8/CD4 to HLAI and HLAII. 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