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Barile G. The fixation of complement protein pairs to CR2 isoforms. Biochem Biophys Rep 2024; 38:101657. [PMID: 38371315 PMCID: PMC10869749 DOI: 10.1016/j.bbrep.2024.101657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 01/26/2024] [Accepted: 01/27/2024] [Indexed: 02/20/2024] Open
Abstract
Reviewing old protocols, it was found that Raji, a CR2-posistive cell line, binds both endogenous (e-C3) and exogenous C3 (i-C3). The processing of i-C3 to an i-C3b-like protein and their fixation to CR2 isoforms resulted in the formation of heterodimers whose units might be linked via thioester by low m.w. molecule(s). In an attempt to study the origin of the low m.w. molecules, it was found that they were detected following I12⁵-C3d treatment with NHS or hi-S. Indirect evidence would suggest that the products of C3 fragment fixation could have a short half-life and that the aromatic residues present in C3d might have different physico-chemical characteristics than those present in C3c. The surface hydrophobicity expressed by these aromatic residues could be required for the fixation of C3 or CR2 fragments to cell surface proteins.
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Affiliation(s)
- Giuseppe Barile
- Former Dirigente di Ricerca, Istituto Tecnologie Biomediche, CNR, Roma, Italy
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2
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Ma Y, Liu Y, Zhang Z, Yang GY. Significance of Complement System in Ischemic Stroke: A Comprehensive Review. Aging Dis 2019; 10:429-462. [PMID: 31011487 PMCID: PMC6457046 DOI: 10.14336/ad.2019.0119] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 01/19/2019] [Indexed: 12/14/2022] Open
Abstract
The complement system is an essential part of innate immunity, typically conferring protection via eliminating pathogens and accumulating debris. However, the defensive function of the complement system can exacerbate immune, inflammatory, and degenerative responses in various pathological conditions. Cumulative evidence indicates that the complement system plays a critical role in the pathogenesis of ischemic brain injury, as the depletion of certain complement components or the inhibition of complement activation could reduce ischemic brain injury. Although multiple candidates modulating or inhibiting complement activation show massive potential for the treatment of ischemic stroke, the clinical availability of complement inhibitors remains limited. The complement system is also involved in neural plasticity and neurogenesis during cerebral ischemia. Thus, unexpected side effects could be induced if the systemic complement system is inhibited. In this review, we highlighted the recent concepts and discoveries of the roles of different kinds of complement components, such as C3a, C5a, and their receptors, in both normal brain physiology and the pathophysiology of brain ischemia. In addition, we comprehensively reviewed the current development of complement-targeted therapy for ischemic stroke and discussed the challenges of bringing these therapies into the clinic. The design of future experiments was also discussed to better characterize the role of complement in both tissue injury and recovery after cerebral ischemia. More studies are needed to elucidate the molecular and cellular mechanisms of how complement components exert their functions in different stages of ischemic stroke to optimize the intervention of targeting the complement system.
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Affiliation(s)
- Yuanyuan Ma
- 1Department of Neurology, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.,2Med-X Research Institute and School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Yanqun Liu
- 3Department of Neurology, Changhai Hospital, Second Military Medical University, Shanghai, China
| | - Zhijun Zhang
- 2Med-X Research Institute and School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Guo-Yuan Yang
- 1Department of Neurology, Ruijin Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.,2Med-X Research Institute and School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
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3
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Kulik L, Hewitt FB, Willis VC, Rodriguez R, Tomlinson S, Holers VM. A new mouse anti-mouse complement receptor type 2 and 1 (CR2/CR1) monoclonal antibody as a tool to study receptor involvement in chronic models of immune responses and disease. Mol Immunol 2015; 63:479-88. [PMID: 25457881 DOI: 10.1016/j.molimm.2014.10.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 10/03/2014] [Indexed: 12/28/2022]
Abstract
Although reagents are available to block mouse complement receptor type 2 and/or type 1 (CR2/CR1, CD21/CD35) function in acute or short term models of human disease, a mouse anti-rat antibody response limits their use in chronic models. We have addressed this problem by generating in Cr2−/− mice a mouse monoclonal antibody (mAb 4B2) to mouse CR2/CR1. The binding of murine mAb 4B2 to CR2/CR1 directly blocked C3dg (C3d) ligand binding. In vivo injection of mAb 4B2 induced substantial down regulation of CR2 and CR1 from the B cell surface, an effect that lasted six weeks after a single injection of 2 mg of mAb. The 4B2 mAb was studied in vivo for the capability to affect immunological responses to model antigens. Pre-injection of mAb 4B2 before immunization of C57BL/6 mice reduced the IgG1 antibody response to the T-dependent antigen sheep red blood cells (SRBC) to a level comparable to that found in Cr2−/− mice. We also used the collagen-induced arthritis (CIA) model, a CR2/CR1-dependent autoimmune disease model, and found that mice pre-injected with mAb 4B2 demonstrated substantially reduced levels of pathogenic IgG2a antibodies to both the bovine type II collagen (CII) used to induce arthritis and to endogenous mouse CII. Consistent with this result, mice pre-injected with mAb 4B2 demonstrated only very mild arthritis. This reduction in disease, together with published data in CII-immunized Cr2−/− mice, confirm both that the arthritis development depends on CR2/CR1 receptors and that mAb 4B2 can be used to induce biologically relevant receptor blockade. Thus mAb 4B2 is an excellent candidate for use in chronic murine models to determine how receptor blockage at different points modifies disease activity and autoantibody responses.
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MESH Headings
- Animals
- Antibodies, Monoclonal/administration & dosage
- Antibodies, Monoclonal/immunology
- Antibodies, Monoclonal/pharmacology
- Antibody Specificity/immunology
- Antigens/immunology
- Antigens, CD19/metabolism
- Arthritis, Experimental/blood
- Arthritis, Experimental/immunology
- Arthritis, Experimental/pathology
- Autoantibodies/blood
- B-Lymphocytes/cytology
- B-Lymphocytes/drug effects
- Cattle
- Cell Death/drug effects
- Chronic Disease
- Disease Models, Animal
- Down-Regulation/drug effects
- Erythrocytes/drug effects
- Erythrocytes/immunology
- Female
- Immune System Diseases/immunology
- Immunity, Humoral/drug effects
- Immunity, Innate/drug effects
- Immunoglobulin D/metabolism
- Mice, Inbred C57BL
- Rats
- Receptors, Complement 3b/immunology
- Receptors, Complement 3d/immunology
- Sheep
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Affiliation(s)
- Liudmila Kulik
- Division of Rheumatology, Department of Medicine, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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4
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Zhang J, Perelson AS. Contribution of follicular dendritic cells to persistent HIV viremia. J Virol 2013; 87:7893-901. [PMID: 23658450 PMCID: PMC3700220 DOI: 10.1128/jvi.00556-13] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 05/01/2013] [Indexed: 11/20/2022] Open
Abstract
HIV-1 infections cannot be completely eradicated by drug therapy, as the virus persists in reservoirs. Low-level plasma viremia has been detected in patients treated for over 7 years, but the cellular compartments that support this low-level viremia have not been identified. The decay of HIV-1 during treatment appears to occur in four phases, with the 3rd and 4th phases occurring when the virus is below the limit of detection of conventional assays. Here, we focus on the 3rd phase of decay, which has been estimated to have a half-life of 39 months. We show that follicular dendritic cells (FDC), which have been identified as an HIV reservoir, can be the main source of the low-level viremia detected during the 3rd phase of decay and contribute to viremia at even longer times. Our calculations show that the kinetics of leakage of virus from FDC is consistent with three types of available clinical data.
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Affiliation(s)
- Jingshan Zhang
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
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5
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Korir JC, Magambo JK, Mwatha JK, Waitumbi JN. B-cell activity in children with malaria. Malar J 2012; 11:66. [PMID: 22405566 PMCID: PMC3325160 DOI: 10.1186/1475-2875-11-66] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Accepted: 03/09/2012] [Indexed: 11/20/2022] Open
Abstract
Background Recent studies implicate deficiency of red blood cell (RBC) complement regulatory proteins (CR1 and CD55) in the pathogenesis of malarial anaemia. This study explored the involvement of B cell CD21, which has an analogous role to RBC CR1. Methods In a case control study conducted in Kisumu District hospital, western Kenya, children with severe malaria anaemia (SMA) and those with uncomplicated malaria (UM) were assessed by flow cytometry for B cells (CD20+) numbers, expression levels of CD21 and deposition of C3dg and by ELISA for soluble CD21 (sCD21). Paired t tests were used to determine statistical significance at a = 0.05. Results Children with SMA had significantly higher lymphocyte count (9,627.7 ± 8786.1 SD vs. 5,507 ± 2436 SD, P = 0.04 in the UM group) and the computed geometric mean of mature B-cell numbers based on the absolute lymphocyte count was significantly higher for SMA group: 1,823 (1,126 to 2,982, 95% CI) and 826.6 (564 to 1,220, 95% CI)] for UM group (P = 0.003). SMA group also had a higher percentage of CD20+ B cells (26.8 ± 9.7SD vs 20.9 ± 9.01 SD in the UM) (P = 0.03), indicating considerable polyclonal B-cell activation. The CD21 median flourescence intensity was lower in the SMA (246.4 ± 87.4 SD vs 369 ± 137.7 SD) (P <0.0001), probably due to complement mediated shaving of CD21 by fixed tissue macrophages. The CD20+ B cells of SMAs had higher levels of the complement split product C3dg (18.35 ± 10 SD vs 11.5 ± 6.8 S.D), (P = 0.0002), confirming possible role of complement in CD21 removal. Unexpectedly, the SMAs had lower levels of sCD21 (226.5 ± 131.5 SD vs 341.4 ± 137.3 SD in the UM) (P < 0.0001), indicating that the shaved CD21 is not released to peripheral circulation. Conclusions These results implicate B-cell in pathophysiology of severe malaria that involves increased B-cell proliferation, increased complement deposition and subsequent loss of membrane-bound CD21. The loss of CD21 is not by the classical enzmatic cleavage.
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Affiliation(s)
- Jackson C Korir
- Walter Reed Project/Kenya Medical Research Institute, Kisumu, Kenya
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6
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Cooper AM, Hobson PS, Jutton MR, Kao MW, Drung B, Schmidt B, Fear DJ, Beavil AJ, McDonnell JM, Sutton BJ, Gould HJ. Soluble CD23 controls IgE synthesis and homeostasis in human B cells. THE JOURNAL OF IMMUNOLOGY 2012; 188:3199-207. [PMID: 22393152 DOI: 10.4049/jimmunol.1102689] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
CD23, the low-affinity receptor for IgE, exists in membrane and soluble forms. Soluble CD23 (sCD23) fragments are released from membrane (m)CD23 by the endogenous metalloprotease a disintegrin and metalloprotease 10. When purified tonsil B cells are incubated with IL-4 and anti-CD40 to induce class switching to IgE in vitro, mCD23 is upregulated, and sCD23 accumulates in the medium prior to IgE synthesis. We have uncoupled the effects of mCD23 cleavage and accumulation of sCD23 on IgE synthesis in this system. We show that small interfering RNA inhibition of CD23 synthesis or inhibition of mCD23 cleavage by an a disintegrin and metalloprotease 10 inhibitor, GI254023X, suppresses IL-4 and anti-CD40-stimulated IgE synthesis. Addition of a recombinant trimeric sCD23 enhances IgE synthesis in this system. This occurs even when endogenous mCD23 is protected from cleavage by GI254023X, indicating that IgE synthesis is positively controlled by sCD23. We show that recombinant trimeric sCD23 binds to cells coexpressing mIgE and mCD21 and caps these proteins on the B cell membrane. Upregulation of IgE by sCD23 occurs after class-switch recombination, and its effects are isotype-specific. These results suggest that mIgE and mCD21 cooperate in the sCD23-mediated positive regulation of IgE synthesis on cells committed to IgE synthesis. Feedback regulation may occur when the concentration of secreted IgE becomes great enough to allow binding to mCD23, thus preventing further release of sCD23. We interpret these results with the aid of a model for the upregulation of IgE by sCD23.
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Affiliation(s)
- Alison M Cooper
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, Guy's Hospital, London SE1 9RT, UK
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7
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Carter CJ. Epstein-Barr and other viral mimicry of autoantigens, myelin and vitamin D-related proteins and of EIF2B, the cause of vanishing white matter disease: massive mimicry of multiple sclerosis relevant proteins by the Synechococcus phage. Immunopharmacol Immunotoxicol 2011; 34:21-35. [PMID: 21486137 DOI: 10.3109/08923973.2011.572262] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The Epstein-Barr virus expresses proteins containing numerous short consensi (identical pentapeptides at least, or longer gapped consensi) that are identical to those in 16 multiple sclerosis autoantigens or in the products of multiple sclerosis susceptibility genes. Other viruses implicated in multiple sclerosis also display such mimicry and the Synechococcus phage was identified as a novel and major contributor to this phenomenon. Cyanobacteria hosts of Synechococcus phage favor temperate climes, in line with multiple sclerosis distribution, and bacterial and phage ecology accords closely with multiple sclerosis epidemiology. Bovine, ovine or canine viral proteins were also identified as autoantigen homologues, in line with epidemiological data linking multiple sclerosis to cattle density, sheep contact and dog ownership. Viral proteins align with known autoantigens, other myelin and vitamin D-related proteins and the translation initiation factor EIF2B, which is implicated in vanishing white matter disease. These data suggest that the autoantigens in multiple sclerosis, which causes demyelination in animal models, may be generated by antibodies raised to viral protein homologues. Multiple autoantibodies may cause multiple sclerosis via protein knockdown and immune activation. Their selective removal may be of clinical benefit as already suggested by promising results using plasmapheresis or immunoadsorption in certain multiple sclerosis patients.
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Affiliation(s)
- C J Carter
- PolygenicPathways, Saint Leonards-on-sea, East Sussex, UK.
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8
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Human complement receptor type 2 (CR2/CD21) transgenic mice provide an in vivo model to study immunoregulatory effects of receptor antagonists. Mol Immunol 2011; 48:883-94. [DOI: 10.1016/j.molimm.2010.12.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 12/16/2010] [Accepted: 12/20/2010] [Indexed: 01/12/2023]
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9
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Abstract
Complement activation is one of the most powerful mechanisms taking place during inflammation and immune responses. Over the last 30 years increasing evidence has proven the role of C3 and receptors for its activation fragments in the initiation and regulation of immune responses. Since complement also has a basic importance in the maintenance of immune homeostasis, abnormalities affecting complement proteins and their receptors may lead to pathological conditions. Autoimmune conditions develop as a result of a range of genetic and environmental factors. Findings obtained from animal models support the notion that malfunctioning of complement receptors, particularly CR2, might be involved in the breakdown of tolerance and excessive antibody production by auto reactive B-cell clones. In addition to B cells, activated, CR2-bearing T cells may also contribute to the pathogenesis of autoimmunity as they can receive activating/survival signals in the inflamed tissue. Results obtained from mouse experiments however, should be extended to the human system with great care, since there are basic differences between the structure and function of human and murine CR1 and CR2.
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Affiliation(s)
- Andrea Isaák
- Department of Immunology, Eötvös Loránd University, Pázmány P.s.1/C, 1117 Budapest, Hungary
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10
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Wagner C, Hänsch GM. Receptors for complement C3 on T-lymphocytes: Relics of evolution or functional molecules? Mol Immunol 2006; 43:22-30. [PMID: 16019070 DOI: 10.1016/j.molimm.2005.06.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Despite the fact that receptors for complement on T-cells have been described many years ago the function remains unclear as is the role of complement in the T-cell response. In this review we will evaluate how the accumulated wisdom concur with the current concepts of the adaptive T-cell response.
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Affiliation(s)
- Christof Wagner
- Institut für Immunologie der Universitäl Heidelberg, Im Neuenheimer Feld 305, 69120 Heidelberg, Germany
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11
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Lindorfer MA, Jinivizian HB, Foley PL, Kennedy AD, Solga MD, Taylor RP. B cell complement receptor 2 transfer reaction. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2003; 170:3671-8. [PMID: 12646632 DOI: 10.4049/jimmunol.170.7.3671] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The B cell C receptor specific for C3dg (CR2) shares a number of features with the primate E C receptor (CR1). Previously, we have demonstrated, both in vitro and in animal models, that immune complexes (IC) bound to primate E CR1, either via C opsonization or by means of bispecific mAb complexes, can be transferred to acceptor macrophages in a process that also removes CR1 from the E. We have now extended this paradigm, the transfer reaction, to include B cell CR2. We used both flow cytometry and fluorescence microscopy to demonstrate that IC bound to Raji cell CR2, either via C opsonization or through the use of an anti-CR2 mAb, are transferred to acceptor THP-1 cells. This reaction, which appears to require Fc recognition of IgG bound to Raji cell CR2, also leads to transfer of CR2. Additional support for the B cell transfer reaction is provided in a prototype study in a monkey model in which IC bound to B cell CR2 are localized to the spleen. These findings may have important implications with respect to defining the role of C in IC handling during the normal immune response.
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Affiliation(s)
- Margaret A Lindorfer
- Department of Biochemistry and Molecular Genetics, University of Virginia Health Sciences Center, Charlottesville, VA 22908-0733, USA
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12
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Abstract
Neonates produce lower levels of IgE compared with adults. Diminished IL-4 production and impaired up-regulation of CD40L by neonatal T cells could explain this, however other regulators of IgE production, such as CD21 and CD23, could contribute to reduced circulating IgE levels during fetal development. Heparinized blood samples were collected from adults and from the umbilical cord at premature and term births. Whole blood flow cytometry was used to assess the percentage of T (CD3(+)) and B (CD19(+)) lymphocytes expressing CD21 and/or CD23 at 26-29 (n = 3), 30-33 (n = 7), 34-37 (n = 5), and >37 (n = 11) wk of gestation, as well as in adults (n = 15). Plasma-soluble CD21 was also measured. At term, the percentage of CD21(+) and CD23(+) B cells was comparable to the adult, however, the percentage of cells positive for each of these surface antigens was decreased significantly before term. The percentage of T cells expressing CD21 from all gestations was significantly higher than the adult and the percentage positive decreased with increasing gestational age. Conversely, soluble CD21 levels increased with increasing gestation to be comparable to the adult by term. Thus, it is unlikely that altered expression of CD21 and CD23 on B cells contributes to the low level of IgE in the neonatal circulation unless functional differences occur or a lack of processing to the soluble form is important in regulating IgE production. However the abundance of CD21-positive T cells could alter the T- and B-cell interaction necessary for IgE switching by B cells and, thereby, especially with impaired IL-4 production, limit IgE production.
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Affiliation(s)
- Catherine A Thornton
- Allergy and Inflammation Sciences, School of Medicine, University of Southampton, SO16 6YD, UK.
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13
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Hlavacek WS, Percus JK, Percus OE, Perelson AS, Wofsy C. Retention of antigen on follicular dendritic cells and B lymphocytes through complement-mediated multivalent ligand-receptor interactions: theory and application to HIV treatment. Math Biosci 2002; 176:185-202. [PMID: 11916508 DOI: 10.1016/s0025-5564(02)00091-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In HIV-infected patients, large quantities of HIV are associated with follicular dendritic cells (FDCs) in lymphoid tissue. During antiretroviral therapy, most of this virus disappears after six months of treatment, suggesting that FDC-associated virus has little influence on the eventual outcome of long-term therapy. However, a recent theoretical study using a stochastic model for the interaction of HIV with FDCs indicated that some virus may be retained on FDCs for years, where it can potentially reignite infection if treatment is interrupted. In that study, an approximate expression was used to estimate the time an individual virion remains on FDCs during therapy. Here, we determine the conditions under which this approximation is valid, and we develop expressions for the time a virion spends in any bound state and for the effect of rebinding on retention. We find that rebinding, which is influenced by diffusion, may play a major role in retention of HIV on FDCs. We also consider the possibility that HIV is retained on B cells during therapy, which like FDCs also interact with HIV. We find that virus associated with B cells is unlikely to persist during therapy.
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Affiliation(s)
- William S Hlavacek
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
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14
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Mongini PK, Inman JK. Cytokine dependency of human B cell cycle progression elicited by ligands which coengage BCR and the CD21/CD19/CD81 costimulatory complex. Cell Immunol 2001; 207:127-40. [PMID: 11243702 DOI: 10.1006/cimm.2001.1758] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Coengagement of BCR and the C3dg binding CD21/CD19/CD81 costimulatory complex can profoundly reduce the BCR binding threshold for eliciting B cell S phase entry, provided cytokine is present. IL-4 is substantially better than IL-2, IL-13, and TNF-alpha at exhibiting synergy with BCR:CD21 coengaging ligand (anti-IgM:anti-CD21:dextran) in promoting B cell DNA synthesis. Synergy between IL-4 and anti-IgM:anti-CD21:dextran (a) is not explained by the viability-promoting function of IL-4, (b) occurs when the anti-CD21 moiety engages either C3dg binding or non-C3dg binding domains, (c) does not reflect reversal of FcgammaRII-mediated negative regulation, and (d) involves differing temporal requirements for BCR and IL-4R signal transduction during the activation process. The IL-4R signaling pathway appears to synergize directly with the BCR:CD21 signaling pathway(s) in promoting the progression of resting B cells past an early G1 checkpoint, as well as to promote independently the progression of activated B cells past a later G1 to S checkpoint.
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Affiliation(s)
- P K Mongini
- Department of Rheumatology, Hospital for Joint Diseases, New York, New York 10003, USA
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15
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Reinagel ML, Taylor RP. Transfer of immune complexes from erythrocyte CR1 to mouse macrophages. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 164:1977-85. [PMID: 10657648 DOI: 10.4049/jimmunol.164.4.1977] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We are developing a potential therapeutic approach for removing pathogens from the circulation of primates in which the pathogen is bound to the complement receptor (CR1) on E using a bispecific mAb complex, a heteropolymer (HP). We have used mAb this approach to demonstrate that cleared prototype pathogens are localized to, phagocytosed in, and destroyed in the liver. Extension of this work to a clinical setting will require a detailed understanding of the mechanism by which the E-bound immune complex substrates are transferred to fixed tissue macrophages in the liver, the transfer reaction. Therefore, we examined an in vitro system to study this process using bacteriophage phiX174 as a model pathogen. E containing phiX174 (bound via an anti-CR1/anti-phiX174 HP) were incubated with P388D1 murine macrophages, and the two cell types were separated by centrifugation through Ficoll. Both E and macrophages were then probed and analyzed by RIA or flow cytometry. The results indicate that all three components of the E-bound IC (phiX174, HP, and CR1) were removed from the E and internalized by the macrophages. We found that transfer requires the Fc portion of IgG, because little transfer of phiX174 occurs when it is bound to E CR1 using a HP containing only Fab fragments. These findings, taken in the context of other studies, suggest a general mechanism for the transfer reaction in which Fc receptors facilitate close juxtaposition of the macrophage to the E-bound IC which then allows a macrophage-associated protease to cleave CR1. The released IC are then internalized and processed by the macrophages.
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Affiliation(s)
- M L Reinagel
- Department of Biochemistry, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
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16
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Hlavacek WS, Wofsy C, Perelson AS. Dissociation of HIV-1 from follicular dendritic cells during HAART: mathematical analysis. Proc Natl Acad Sci U S A 1999; 96:14681-6. [PMID: 10611272 PMCID: PMC24707 DOI: 10.1073/pnas.96.26.14681] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Follicular dendritic cells (FDC) provide a reservoir for HIV type 1 (HIV-1) that may reignite infection if highly active antiretroviral therapy (HAART) is withdrawn before virus on FDC is cleared. To estimate the treatment time required to eliminate HIV-1 on FDC, we develop deterministic and stochastic models for the reversible binding of HIV-1 to FDC via ligand-receptor interactions and examine the consequences of reducing the virus available for binding to FDC. Analysis of these models shows that the rate at which HIV-1 dissociates from FDC during HAART is biphasic, with an initial period of rapid decay followed by a period of slower exponential decay. The speed of the slower second stage of dissociation and the treatment time required to eradicate the FDC reservoir of HIV-1 are insensitive to the number of virions bound and their degree of attachment to FDC before treatment. In contrast, the expected time required for dissociation of an individual virion from FDC varies sensitively with the number of ligands attached to the virion that are available to interact with receptors on FDC. Although most virions may dissociate from FDC on the time scale of days to weeks, virions coupled to a higher-than-average number of ligands may persist on FDC for years. This result suggests that HAART may not be able to clear all HIV-1 trapped on FDC and that, even if clearance is possible, years of treatment will be required.
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Affiliation(s)
- W S Hlavacek
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
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17
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Nardin A, Lindorfer MA, Taylor RP. How are immune complexes bound to the primate erythrocyte complement receptor transferred to acceptor phagocytic cells? Mol Immunol 1999; 36:827-35. [PMID: 10698336 DOI: 10.1016/s0161-5890(99)00103-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Immune complexes (IC) bound to the primate erythrocyte (E) complement receptor (CR1) are cleared from the circulation of primates and localized to phagocytic cells in the liver and spleen without E destruction. IC can be bound to E CRI either via C3b opsonization or with cross-linked mAb complexes (heteropolymers, HP) which contain a mAb specific for CRI and a mAb specific for an antigen. The long-term goal of our work is to apply the HP system to the treatment of human diseases associated with blood-borne pathogens. This review discusses the mechanism by which the E-bound IC are transferred to acceptor cells. Our studies in animal models as well as our in vitro investigations indicate that IC transfer is rapid (usually >90% in 10 min) and does not lead to lysis or phagocytosis of the E. Experiments with specific inhibitors and the use of IC prepared with Fab' fragments suggest that transfer depends mainly upon recognition by Fc receptors on the acceptor cell. Moreover, we find that IC release from the E is associated with a concerted loss of CR1, and is followed by uptake and internalization of the IC by the acceptor cell. We suggest that recognition and binding of the E-bound IC substrates by Fc receptors allows close contact between the E and acceptor cells, which in turn facilitates proteolysis of E CR1, presumably by a macrophage-associated protease. After proteolysis, the released IC are internalized by the macrophages.
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Affiliation(s)
- A Nardin
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville 22908, USA
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18
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Nardin A, Schlimgen R, Holers VM, Taylor RP. A prototype pathogen bound ex vivo to human erythrocyte complement receptor 1 via bispecific monoclonal antibody complexes is cleared to the liver in a mouse model. Eur J Immunol 1999; 29:1581-6. [PMID: 10359112 DOI: 10.1002/(sici)1521-4141(199905)29:05<1581::aid-immu1581>3.0.co;2-v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Immune complexes (IC) bound to the primate erythrocyte (E) complement receptor (CR1) are cleared from the circulation of primates and localized to the liver. IC can be bound to E CR1 either via C3b opsonization or with cross-linked mAb complexes (heteropolymers, HP) which contain an mAb specific for CR1 and a mAb specific for a prototype pathogen. The long-term goal of our work is to apply the HP to the treatment of human diseases associated with blood-borne pathogens. Therefore we have investigated the feasibility of a non-primate model by studying clearance in mice of bacteriophage phiX174 bound via HP to primate E. E-HP-phiX174 complexes were prepared in vitro and infused into the circulation of mice under conditions allowing short term survival of E in the circulation. By radioimmunoassays and flow cytometry, we found that phiX174 is removed from E and cleared from the circulation coincident with loss of HP and CR1, and that the majority of cleared phiX174 is localized to the liver. Through the use of HP constructed with Fab' fragments, we verified the requirement for the Fc portion of the mAb in clearance; inhibition of C3 activation delayed clearance, suggesting a role for complement. The present findings in the mouse confirm previous observations in the non-human primate model.
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Affiliation(s)
- A Nardin
- Department of Biochemistry, University of Virginia School of Medicine, Charlottesville 22908, USA
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19
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Frémeaux-Bacchi V, Kolb JP, Rakotobé S, Kazatchkine MD, Fischer EM. Functional properties of soluble CD21. IMMUNOPHARMACOLOGY 1999; 42:31-7. [PMID: 10408363 DOI: 10.1016/s0162-3109(99)00026-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Soluble receptors may display immunoregulatory properties by blocking interactions between ligands and their membrane receptors or by triggering specific biologic responses through interaction with counter part membrane receptors. A natural soluble form of CD21 that is cleaved from lymphocyte membrane CD21 circulates in normal human serum. Soluble CD21 retains the capacity to bind iC3b and CD23, the known ligands of membrane CD21. In a similar fashion to IgE complexes, another ligand of CD23, the soluble CD21 was shown to efficiently trigger CD23-signalling pathways in human monocytes. By inducing release of proinflammatory cytokines and upregulating expression of molecules involved in antigen presentation, soluble CD21 modulates critical monocyte functions that may be relevant to allergic and inflammatory disorders.
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Affiliation(s)
- V Frémeaux-Bacchi
- INSERM U430 and Université Pierre et Marie Curie, Hopital Broussais, Paris, France
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20
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Prodinger WM. Complement receptor type two (CR2,CR21): a target for influencing the humoral immune response and antigen-trapping. Immunol Res 1999; 20:187-94. [PMID: 10741859 DOI: 10.1007/bf02790402] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cellular receptors for complement C3 fragments deposited on antigens are important bricks in the wall defending against microbial pathogens. The part of complement receptor type 2 (CR2; CD21) deals with enhancing humoral immune responses and with long-term trapping of C3d-coated antigen by follicular dendritic cells. CR2 is also pivotal for Epstein-Barr virus (EBV) infection. Here, the current understanding, how CR2 interacts with its ligands C3d, EBV, and CD23 is summarized. The potential to target CR2 for clinical therapy or immunization purposes are discussed.
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Affiliation(s)
- W M Prodinger
- Institut für Hygiene, University of Innsbruck, Austria.
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21
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Frémeaux-Bacchi V, Aubry JP, Bonnefoy JY, Kazatchkine MD, Kolb JP, Fischer EM. Soluble CD21 induces activation and differentiation of human monocytes through binding to membrane CD23. Eur J Immunol 1998; 28:4268-74. [PMID: 9862364 DOI: 10.1002/(sici)1521-4141(199812)28:12<4268::aid-immu4268>3.0.co;2-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Interactions between CD23, the low-affinity receptor for IgE, and CD21, the C3d/EBV receptor, modulate several intracellular events in lymphocytes. A soluble form of CD21 (sCD21) corresponding to the extracellular domain of the receptor circulates in normal plasma. We now demonstrate that purified sCD21 acts as a functional ligand for CD23-expressing monocytes. Soluble CD21 induced an increase in intracellular cGMP levels and the production of IL-6 and TNF-alpha in IL-4-pretreated monocytes induced to express CD23 but not in unstimulated CD23- monocytes. The accumulation of cGMP and the production of TNF-alpha were inhibited by NG-monomethyl-L-arginine (L-NMMA), indicating that sCD21 activates the L-arginine pathway of NO production. We demonstrated that sCD21 activates NO synthase (NOS) since it was found to enhance the conversion of L-arginine into L-citrulline and induce the intracellular expression of inducible NOS in CD23+ monocytes. In addition, sCD21 was shown to up-regulate the expression of HLA-DR and CD40 and decrease that of CD14 on cultured CD23+ monocytes. Thus, in a fashion similar to IgE complexes, sCD21 is able to efficiently trigger CD23 signaling pathways, inducing the release of pro-inflammatory mediators by human monocytes. Soluble CD21 up-regulates the expression of molecules involved in antigen presentation, further suggesting a potential immunoregulatory function for the soluble molecule.
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22
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Li CG, Wilson PB, Bernabeu C, Raab U, Wang JM, Kumar S. Immunodetection and characterisation of soluble CD105-TGFbeta complexes. J Immunol Methods 1998; 218:85-93. [PMID: 9819125 DOI: 10.1016/s0022-1759(98)00118-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
CD105 (endoglin) is a receptor for transforming growth factor beta (TGFbeta). Although methods to measure soluble forms of TGFbeta and CD105 have been published, no assay is available to quantify the receptor-ligand complexes. We describe both an indirect enzyme-linked immunosorbent assay for the quantitation of soluble CD105-TGFbeta1 and the characterization of the complexes by immunoprecipitation and immunoblotting. Mab E9, specifically reactive with CD105, was utilised as the capture reagent in the ELISA system. Detection of complexes was achieved using chicken antibody against TGFbeta1 and the subsequent detection of bound antibody demonstrated by the addition of anti-species antiserum conjugated to horseradish peroxidase (HRP). By using enhanced chemiluminescence and optimised antibodies, the assay was made sufficiently sensitive and reproducible to detect low levels of circulating complexes. Whether the assay had any practical applications was evaluated in breast cancer patients. Plasma levels of CD105-TGFbeta1 were significantly elevated in 59 patients with breast cancer compared to 52 age matched normal women (p < 0.001). Immunoprecipitation using a rabbit anti-CD105 antibody, which reacts with both dimeric and monomeric CD105, and immunoblotting showed that three molecular forms of CD105-TGFbeta1 complexes > 200, 195, and 125 kDa existed in the plasma. We believe these represent the oligomer, dimer and probably the protease degraded form of CD105 complexed to TGFbeta1. The resistance to hypertonic solution, SDS and heat treatment suggested that the soluble CD105-TGFbeta1 complex may be linked by covalent bonds. The measurement of CD105-TGFbeta complexes in the circulation may have important clinical applications not only in cancer but also in patients with other angiogenic diseases such as rheumatoid arthritis, myocardial infarction and stroke.
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Affiliation(s)
- C G Li
- Department of Pathological Sciences, Medical School, The University, Manchester, UK
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23
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Bonnefoy JY, Lecoanet-Henchoz S, Gauchat JF, Graber P, Aubry JP, Jeannin P, Plater-Zyberk C. Structure and functions of CD23. Int Rev Immunol 1998; 16:113-28. [PMID: 9651788 DOI: 10.3109/08830189709045705] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
This review summarizes recent data on CD23, a low affinity receptor for IgE (Fc epsilon RII). CD23 is the only FcR which does not belong to the immunoglobulin gene superfamily. The CD23 molecule was discovered independently as an IgE receptor on human lymphoblastoid B cells [1], as a cell surface marker expressed on Epstein-Barr-Virus-transformed B cells (EBVCS) [2] and as a B-cell activation antigen (Blast 2) [3]. CD23 was shown to be a low affinity receptor for IgE [4,5]. Similar to most FcR, soluble forms of CD23 (sCD23) are released into extracellular fluids. The soluble fragments formed by proteolytic cleavage of surface CD23 are not only capable of binding IgE (IgE binding factors) but also exhibit multiple functions that are not IgE related. These observations together with the finding that CD23 displays significant homology with Ca(2+)-dependent (C-type) animal lectins, suggested the existence of natural ligands other than IgE. The recent finding that CD23 interacts with CD21, CD11b and CD11c indicates that CD23 should be viewed not only as a low affinity IgE receptor but also as an adhesion molecule involved in cell-cell interaction. After a brief overview of the molecular structure, there follows a discussion of the biological activities ascribed to human CD23.
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Affiliation(s)
- J Y Bonnefoy
- Geneva Biomedical Research Institute, Immunology Department, Geneva, Switzerland
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24
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Jeannin P, Lecoanet-Henchoz S, Delneste Y, Gauchat JF, Bonnefoy JY. Alpha-1 antitrypsin up-regulates human B cell differentiation selectively into IgE- and IgG4- secreting cells. Eur J Immunol 1998; 28:1815-22. [PMID: 9645362 DOI: 10.1002/(sici)1521-4141(199806)28:06<1815::aid-immu1815>3.0.co;2-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Numerous allergens have proteolytic activities. It has been speculated that this property may contribute to their allergenicity. Therefore, we have evaluated the effect of different physiological protease inhibitors (PI) on the regulation of human IgE synthesis. Unexpectedly, the serine PI, alpha-1 antitrypsin, also called alpha-1 protease inhibitor (alpha1PI), induced a potent and selective dose-dependent increase of IgE and IgG4 production by human tonsillar B cells stimulated with the IgE and IgG4 switch factors, IL-4 and anti-CD40 mAb. The other serine PI tested were inefficient. Furthermore, this effect of alpha1PI was accompanied by an increase in (1) germ-line and mature sigma mRNA transcription, (2) proliferation and (3) membrane CD23 and CD21 expression, while the expression of other molecules involved in the regulation of IgE synthesis was unchanged. Since CD23-CD21 pairing plays a crucial role in the up-regulation of IgE synthesis, we have tested whether blocking this interaction affected alpha1PI-increased IgE production. The neutralizing anti-CD23 mAb, Mab 25, partly reversed the IgE increase caused by alpha1PI. Moreover, alpha1PI potentiation of IgE synthesis was prevented by elastase, a natural substrate of alpha1PI, thereby suggesting that alpha1PI may inhibit endogenous B cell enzyme(s) involved in the down-regulation of IgE synthesis. Alpha1PI also potentiated IgE and IgG4 production by IL-4-stimulated peripheral blood mononuclear cells but was not a switch factor for IgE and IgG4 as it was unable to replace IL-4 or anti-CD40 mAb in inducing IgE and IgG4 production. In conclusion, this study shows that alpha1PI acts as a potent co-stimulus for IgE and IgG4 synthesis and suggests that the equilibrium between protease/ protease inhibitor participates in the control of human IgE and IgG4 synthesis.
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Affiliation(s)
- P Jeannin
- Geneva Biomedical Research Institute, Immunology Department, Glaxo Wellcome R&D SA, Switzerland
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25
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Kuhn SE, Nardin A, Klebba PE, Taylor RP. Escherichia coli Bound to the Primate Erythrocyte Complement Receptor via Bispecific Monoclonal Antibodies Are Transferred to and Phagocytosed by Human Monocytes in an In Vitro Model. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.160.10.5088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
We have prepared cross-linked, bispecific mAb complexes (heteropolymers) that facilitate rapid and quantitative binding of a prototype pathogen, Escherichia coli, to the complement receptor (CR1) on primate erythrocytes. Incubation of the erythrocyte-heteropolymer-E. coli complexes with freshly isolated human mononuclear cells leads to rapid removal of the E. coli from the erythrocytes, and phagocytosis and killing of the bacteria. The erythrocytes are not lysed or phagocytosed during this transfer reaction, but both heteropolymer and CR1 are removed from the erythrocytes along with the E. coli. These findings parallel observations made in previous in vivo experiments in which heteropolymers were used to facilitate clearance of innocuous prototype pathogens in a monkey model. It should now be possible to extend the heteropolymer paradigm to a live pathogen in a primate model.
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Affiliation(s)
- Susan E. Kuhn
- *Department of Biochemistry, University of Virginia School of Medicine, Charlottesville, VA 22908; and
| | - Alessandra Nardin
- *Department of Biochemistry, University of Virginia School of Medicine, Charlottesville, VA 22908; and
| | - Philip E. Klebba
- †Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019
| | - Ronald P. Taylor
- *Department of Biochemistry, University of Virginia School of Medicine, Charlottesville, VA 22908; and
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26
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Frémeaux-Bacchi V, Fischer E, Kazatchkine MD. Membrane and soluble forms of CD21 (the C3dg/EBV receptor). Immunol Lett 1996; 54:201-4. [PMID: 9052878 DOI: 10.1016/s0165-2478(96)02673-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- V Frémeaux-Bacchi
- INSERM U430 and Universite Pierre et Marie Curie, Hopital Broussais, Paris, France
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