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Dempsey LA, Brunn GJ, Platt JL. Heparanase, a potential regulator of cell-matrix interactions. Trends Biochem Sci 2000; 25:349-51. [PMID: 10916150 DOI: 10.1016/s0968-0004(00)01619-4] [Citation(s) in RCA: 146] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Kodaira Y, Nair SK, Wrenshall LE, Gilboa E, Platt JL. Phenotypic and functional maturation of dendritic cells mediated by heparan sulfate. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:1599-604. [PMID: 10903769 DOI: 10.4049/jimmunol.165.3.1599] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Primary immune responses are thought to be induced by dendritic cells. To promote such responses, dendritic cells must be activated by exogenous agonists, such as LPS, or by products of activated leukocytes, such as TNF-alpha and IL-1. How dendritic cells might be activated in the absence of exogenous stimuli, or without the immediate presence of activated leukocytes, as might occur in immunity to tumor cells or transplants, is unknown. We postulated that heparan sulfate, an acidic, biologically active polysaccharide associated with cell membranes and extracellular matrices, which is rapidly released under conditions of inflammation and tissue damage, might provide such a stimulus. Incubation of immature murine dendritic cells with heparan sulfate induced phenotypic maturation evidenced by up-regulation of I-A, CD40, CD54 (ICAM-1), CD80 (B7-1), and CD86 (B7-2). Dendritic cells exposed to heparan sulfate exhibited a markedly lowered rate of Ag uptake and increased allostimulatory capacity. Stimulation of dendritic cells with heparan sulfate induced release of TNF-alpha, IL-1beta, and IL-6, although the maturation of dendritic cells was independent of these cytokines. These results suggest that soluble heparan sulfate chains, as products of the degradation of heparan sulfate proteoglycan, might induce maturation of dendritic cells without exogenous stimuli, thus contributing to the generation and maintenance of primary immune responses.
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Abstract
Xenotransplantation of the liver, in its broadest conception, might involve the transplantation of an intact organ or xenogeneic hepatocytes, or the use of an intact xenogeneic liver or cells as an ex vivo "device." The indications for xenotransplantation include not only hepatic failure but also, potentially, the treatment of metabolic diseases. The hurdles to xenotransplantation include immune, physiologic, and infectious complications. New information and progress in experimental systems are bringing xenotransplantation closer to clinical application.
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Holzknecht ZE, Coombes S, Blocher BA, Plummer TB, Bustos M, Lau CL, Davis RD, Platt JL. Evidence of immunocomplex formation in pulmonary xenografts. Transplant Proc 2000; 32:1141. [PMID: 10936394 DOI: 10.1016/s0041-1345(00)01159-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Holzknecht ZE, Williams JM, Plummer TB, Platt JL. Apoptosis in acute vascular rejection of xenografts. Transplant Proc 2000; 32:973. [PMID: 10936305 DOI: 10.1016/s0041-1345(00)01069-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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206
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Lau CL, Daggett WC, Yeatman MF, Chai P, Lin SS, Lodge AJ, Chen EP, Diamond LE, Byrne GW, Logan JS, Parker W, Platt JL, Davis RD. The role of antibodies in dysfunction of pig-to-baboon pulmonary transplants. J Thorac Cardiovasc Surg 2000; 120:29-38. [PMID: 10884652 DOI: 10.1067/mtc.2000.106841] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE Pulmonary transplantation has become the preferred treatment for end-stage lung disease, but application of the procedure is limited because of a paucity of donors. One way to solve donor limitations is to use animal organs as a donor source or xenotransplantation. The current barrier to pulmonary xenotransplantation is the rapid failure of the pulmonary xenograft. Although antibodies are known to play a role in heart and kidney xenograft rejection, their involvement in lung dysfunction is less defined. This project was designed to define the role of antibodies in pulmonary graft rejection in a pig-to-baboon model. METHODS Orthotopic transgenic swine left lung transplants were performed in baboons depleted of antibodies by one of three techniques before transplantation: (1) ex vivo swine kidney perfusion, (2) total immunoglobulin-depleting column perfusion, and (3) ex vivo swine lung perfusion. Results were compared with those of transgenic swine lung transplants in unmodified baboons. RESULTS All three techniques of antibody removal resulted in depletion of xenoreactive antibodies. Only pretransplantation lung perfusion improved pulmonary xenograft function compared with lung transplantation in unmodified baboons. CONCLUSIONS The pathogenesis of pulmonary injury in a swine-to-primate transplant model is different from that in renal and cardiac xenografts. Depletion of antibodies alone does not have a beneficial effect and may actually be detrimental.
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Mannon RB, Doyle C, Griffiths R, Bustos M, Platt JL, Coffman TM. Altered intragraft immune responses and improved renal function in MHC class II-deficient mouse kidney allografts. Transplantation 2000; 69:2137-43. [PMID: 10852613 DOI: 10.1097/00007890-200005270-00031] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND During renal allograft rejection, expression of MHC class II antigens is up-regulated on the parenchymal cells of the kidney. This up-regulation of MHC class II proteins may stimulate the intragraft alloimmune response by promoting their recognition by recipient CD4+ T cells. In previous studies, absence of donor MHC class II antigens did not affect skin graft survival, but resulted in prolonged survival of cardiac allografts. METHODS To further explore the role of MHC class II antigens in kidney graft rejection, we performed vascularized kidney transplants using donor kidneys from A(beta)b-deficient mice that lack MHC class II expression. RESULTS At 4 weeks after transplant, GFR was substantially depressed in control allografts (2.18+/-0.46 ml/min/kg) compared to nonrejecting isografts (7.98+/-1.62 ml/min/kg; P<0.01), but significantly higher in class II- allografts (4.38+/-0.60 ml/min/kg; P<0.05). Despite the improvement in renal function, class II- allograft demonstrated histologic features of acute rejection, not unlike control allografts. However, morphometric analysis at 1 week after transplantation demonstrated significantly fewer CD4+ T cells infiltrating class II- allografts (12.8+/-1.2 cells/mm2) compared to controls (25.5+/-2.6 cells/mm2; P=0.0007). Finally, the intragraft profile of cytokines was altered in class II- allografts, with significantly reduced expression of Th2 cytokine mRNA compared to controls. CONCLUSIONS These results support a role of MHC class II antigens in the kidney regulating immune cells within the graft. Further, effector pathways triggered by class II antigens promote renal injury during rejection.
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Dempsey LA, Plummer TB, Coombes SL, Platt JL. Heparanase expression in invasive trophoblasts and acute vascular damage. Glycobiology 2000; 10:467-75. [PMID: 10764835 DOI: 10.1093/glycob/10.5.467] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Heparan sulfate proteoglycans play a pivotal role in tissue function, development, inflammation, and immunity. We have identified a novel cDNA encoding human heparanase, an enzyme thought to cleave heparan sulfate in physiology and disease, and have located the HEP gene on human chromosome 4q21. Monoclonal antibodies against human heparanase located the enzyme along invasive extravillous trophoblasts of human placenta and along endothelial cells in organ xenografts targeted by hyperacute rejection, both sites of heparan sulfate digestion. Heparanase deposition was evident in arterial walls in normal tissues; however, vascular heparan sulfate cleavage was coincident with heparanase enzyme during inflammatory episodes. These findings suggest that heparanase elaboration and control of catalytic activity may contribute to the development and pathogenesis of vascular disease and suggest that heparanase intervention might be a useful therapeutic target.
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Saadi S, Holzknecht RA, Patte CP, Platt JL. Endothelial cell activation by pore-forming structures: pivotal role for interleukin-1alpha. Circulation 2000; 101:1867-73. [PMID: 10769290 DOI: 10.1161/01.cir.101.15.1867] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Interaction of complement with endothelial cells (ECs) underlies the development of inflammation and coagulation in disease. Assembly of the membrane attack complex (MAC) of complement on EC membrane, like stimulation with cytokines, upregulates tissue factor and cyclooxygenase-2 but does so via the intermediary action of IL-1alpha. We asked whether the MAC activates porcine aortic and microvascular ECs in a global manner by this mechanism and whether this mechanism is used by membrane pore-forming structures. METHODS AND RESULTS Exposure of ECs to complement caused upregulation of mRNAs for E-selectin, intracellular adhesion molecule-1, vascular cell adhesion molecule-1, Ikappa-Balpha, interleukin (IL)-1alpha, IL-1beta, IL-8, and plasminogen activator inhibitor-1 over a period of 6 hours. The expression of these genes was not a primary response to stimulation, however, because IL-1 receptor antagonist inhibited expression of these genes. Activation of ECs by complement depended on the autocrine action of IL-1alpha, because complement-mediated EC activation was inhibited by anti-IL-1alpha antibodies. Melittin and mastoparan, amphiphilic pore-forming peptides like the MAC, induced E-selectin through intermediary action of IL-1. CONCLUSIONS These findings suggest that transmembrane pore-forming proteins, as a class of molecules, activate ECs through the autocrine effects of IL-1alpha.
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Nagayasu T, Saadi S, Holzknecht RA, Plummer TB, Platt JL. Expression of tissue factor mRNA in cardiac xenografts: clues to the pathogenesis of acute vascular rejection. Transplantation 2000; 69:475-82. [PMID: 10708098 DOI: 10.1097/00007890-200002270-00003] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Acute vascular rejection destroys vascularized xenografts over a period of hours to days and is now considered the major hurdle to the clinical application of xenotransplantation. The hallmark of acute vascular rejection is diffuse intravascular coagulation; however, the pathogenesis of coagulation is a matter of controversy. One line of evidence points to activated endothelial cells and another to activated inflammatory cells as a source of tissue factor and thus as a primary cause of this lesion. The distinction between the two mechanisms inducing coagulation in the xenograft provides an opportunity for specific intervention. METHODS To explore these mechanisms, we studied the expression of tissue factor mRNA by in situ reverse transcriptase-polymerase chain reaction in relation to the histopathologic manifestations of acute vascular rejection in guinea pig hearts transplanted into rats treated by cobra venom factor to avoid the hyperacute rejection. RESULTS Three hours after transplantation and before the deposition of fibrin, tissue factor mRNA was expressed in the endothelial cells lining small and medium blood vessels and in smooth muscle cells of guinea pig cardiac xenografts. Sixteen hours after transplantation, while rat tissue factor mRNA was expressed only in occasional infiltrating cells, cardiac xenografts showed prominent deposits of fibrin in small vessels. Maximum expression of tissue factor on rat infiltrating cells was observed 48 hr after transplantation. CONCLUSIONS These results suggest that in acute vascular rejection, coagulation is initiated on the donor vascular system, while the procoagulant characteristics of infiltrating cells may reflect a response to tissue injury rather than a cause.
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Foley DP, Collins BR, Magee JC, Platt JL, Katz E, Harland RC, Meyers WC, Chari RS. Bile acids in xenogeneic ex-vivo liver perfusion: function of xenoperfused livers and compatibility with human bile salts and porcine livers. Transplantation 2000; 69:242-8. [PMID: 10670634 DOI: 10.1097/00007890-200001270-00009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
BACKGROUND In recent years, hepatic support systems using xenogeneic cells have been developed to support patients in fulminant hepatic failure. The extent to which xenogeneic hepatocytes metabolize and excrete human organic anions is unclear. In these studies we examined the ability of the ex vivo porcine liver to clear human bile acids during extracorporeal liver perfusion (ELP). METHODS Four patients with fulminant hepatic failure underwent extracorporeal liver perfusion with 9 porcine livers. The venovenous circuit was designed as previously described (NEJM,1994,331:234) as were the immunologic features (Transplantation 1994,58:1162). Bile from the porcine liver and serum samples were collected hourly during perfusion. Three bile acids (glycocholic, glycodeoxycholic, taurodeoxycholic acid) were selected as markers for human bile and three (glycohyocholic, glycohyodeoxycholic, and glyco-3alpha-hydroxy-6-oxo-5beta-cholanoic acid) for markers of pig bile. Bile acids from both serum and bile were processed and analyzed through high performance liquid chromatography. The Students' t test was used for statistical analysis. RESULTS The mean duration of perfusions was 4.1+/-1.5 hr. The mean total bile acid clearance from serum (243+/-44 micromol/h) was similar to the total bile acid biliary excretion (286+/-84 micromol/hr, P = 0.06). After 1 hr of perfusion, bile samples demonstrated a predominance of pig bile salts (65%). After 3 hr of perfusion, human bile acids made up 85% of total biliary bile acids. Pig bile acids appeared in patients' sera after 1 hr of perfusion, and after 3 hr, 35% of serum bile salts were pig-specific. CONCLUSIONS Porcine livers perfused with human blood can clear the serum of potentially toxic human bile acids and excrete them into bile. Simultaneously, the percentage of pig-specific bile acids in patient serum increases during xenogeneic perfusion for unknown reasons. The relative hepatic uptake of bile acid from serum is similar to bile acid excretion in bile. Further development of systems using porcine livers or hepatocytes is warranted.
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Nyberg SL, Hibbs JR, Hardin JA, Germer JJ, Platt JL, Paya CV, Wiesner RH. Influence of human fulminant hepatic failure sera on endogenous retroviral expression in pig hepatocytes. Liver Transpl 2000; 6:76-84. [PMID: 10648582 DOI: 10.1002/lt.500060105] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
A porcine endogenous retrovirus (PERV) has been shown to infect human embryonic kidney 293 (HEK293) cells in vitro. The PERV proviral sequence exists in the genome of all porcine cells, including hepatocytes used in a bioartificial liver (BAL). We examined the possibility of PERV infection in HEK293 cells during exposure to supernatant from cultured pig hepatocytes. Pig hepatocytes were cultured in media supplemented with serum from patients in fulminant hepatic failure (FHF) to simulate conditions of an extracorporeal BAL. Pig hepatocytes were cultured in serum-free media for 24 hours and then exposed to fresh medium containing serum from a patient with FHF (22 patients tested). Twenty-four hours later, supernatant was collected and analyzed by polymerase chain reaction (PCR), with and without reverse transcriptase. Primers targeting the pol gene of PERV were used for PCR. Products of amplification were detected by an enzyme-linked immunosorbent assay-based technique using an internal capture probe also targeting the pol gene. Levels of PERV sequences were estimated by serial dilution. All positive samples were tested for infectivity in HEK293 cells. Porcine kidney 15 cell supernatant and fresh culture media were studied as positive and negative controls, respectively. Pig hepatocytes were also studied in the absence of FHF sera and in the presence of mitogenic stimulation with phytohemagglutinin (PHA) and phorbol 12-myristate-13-acetate (PMA). PERV DNA and PERV RNA were detected in all supernatants of cultured pig hepatocytes. The level of PERV RNA in the supernatant of pig hepatocytes was not altered by exposure to human FHF serum or stimulation with PHA and PMA. In addition, PERV RNA was undetectable in the supernatant of HEK293 cells for up to 50 days after exposure to pig hepatocyte supernatant (with or without FHF sera). These findings show that production of PERV by cultured pig hepatocytes was unaffected by exposure to growth factors and cytokines present in human FHF sera.
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Abstract
1. Xenotransplantation, or transplantation across species, leads to rejection, which destroys the xenograft within hours to days of transplantation. 2. Complement is a major barrier to xenotransplantation of vascularized organs and is believed to play an important role in the rejection process. 3. The present paper reviews three aspects of complement in xenotransplantation. These include the mechanisms and regulation of complement activation as well as tissue injury mediated by complement activation.
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Abstract
1. The transplantation of organs and tissues from animals into humans (i.e. xenotransplantation) has been a long sought objective to allow xenotransplantation to achieve its full impact in the clinical practice of medicine. 2. The main hurdles to the application of xenotransplantation are the immunological reaction of the recipient against the transplant, the functional limitations of tissues and organs in biogenetically disparate recipients and the possibility of transferring infectious organisms from the graft into the recipient. 3. Advances in a variety of fields have shed new light on these hurdles and have given rise to potential solutions and prospects for the clinical application of xenotransplant and are summarized in the report that follows.
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Abstract
The major factor limiting the application of allotransplantation for the treatment of renal failure is a severe shortage of donor organs. One approach to overcoming this limitation is the use of kidneys from animals for clinical transplantation, that is xenotransplantation. Although of interest for many years, the application of xenotransplantation has been prevented because of the devastating immune responses of the recipient against the graft. Research conducted in recent years has elucidated the immune mechanisms underlying the rejection of xenografts and has led to the development of incisive therapeutic strategies, including the genetic engineering of donor animals. Success in dealing with the xenogeneic immune response has encouraged the view that xenotransplantation might be feasible in the near future. It also raises consideration of two additional hurdles, the potential limitations of xenogeneic kidneys as physiological replacement for human kidneys and the possibility that the animal organ might transfer infectious organisms to the recipient and to the wider population. This paper reviews recent progress in the field of xenotransplantation of the kidney and offers a perspective on the hurdles to clinical application that remain.
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Wrenshall LE, Platt JL. Regulation of T Cell Homeostasis by Heparan Sulfate-Bound IL-2. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.163.7.3793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Abstract
Although IL-2 is commonly thought to promote proliferation of T lymphocytes, mice deficient in IL-2 exhibit splenomegaly, lymphocytosis, and autoimmunity, suggesting this cytokine may have a prominent role in T cell homeostasis. Since the number of T cells in the bloodstream and lymphoid organs is tightly controlled, it is likely that the availability of IL-2 must also be closely regulated. One mechanism altering the local availability of cytokines is association with heparan sulfate, a glycosaminoglycan found on cell surfaces and within extracellular matrices. Here we show that an association between IL-2 and heparan sulfate localizes IL-2 to lymphoid organs such as the spleen. We also show that IL-2, sequestered in this way, contributes to the activation of T lymphocytes and primes T lymphocytes for activation-induced cell death.
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Wrenshall LE, Platt JL. Regulation of T cell homeostasis by heparan sulfate-bound IL-2. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1999; 163:3793-800. [PMID: 10490977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
Although IL-2 is commonly thought to promote proliferation of T lymphocytes, mice deficient in IL-2 exhibit splenomegaly, lymphocytosis, and autoimmunity, suggesting this cytokine may have a prominent role in T cell homeostasis. Since the number of T cells in the bloodstream and lymphoid organs is tightly controlled, it is likely that the availability of IL-2 must also be closely regulated. One mechanism altering the local availability of cytokines is association with heparan sulfate, a glycosaminoglycan found on cell surfaces and within extracellular matrices. Here we show that an association between IL-2 and heparan sulfate localizes IL-2 to lymphoid organs such as the spleen. We also show that IL-2, sequestered in this way, contributes to the activation of T lymphocytes and primes T lymphocytes for activation-induced cell death.
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220
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Platt JL, Dempsey LA. Accessory function for NK1.1+ natural killer cells producing interferon-gamma in xenospecific cytotoxic T lymphocyte differentiation. Whither the natural killer cell. Transplantation 1999; 68:727-9. [PMID: 10515370 DOI: 10.1097/00007890-199909270-00002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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221
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Wagner E, Platt JL, Howell DN, Marsh HC, Frank MM. IgG and complement-mediated tissue damage in the absence of C2: evidence of a functionally active C2-bypass pathway in a guinea pig model. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1999; 163:3549-58. [PMID: 10477630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
In vitro complement-mediated lysis of heavily sensitized sheep erythrocytes by C4-deficient (C4D) guinea pig and C2-deficient (C2D) human sera was demonstrated some years ago. It was postulated that these "complement-bypass" pathways resulted from activation of C1 and components of the alternative pathway. We used normal, C2D, and C4D guinea pigs in a Forssman shock model to test the in vivo relevance of the C2- and C4-bypass pathways of complement activation. High concentrations of both anti-Forssman Ab and C2D or C4D guinea pig serum induced efficient lysis of sheep erythrocytes in vitro. The most efficient lysis was observed when IgG Ab and C2D guinea pig serum were used. Blocking either the classical pathway (treatments with EGTA-Mg2+ or soluble recombinant complement receptor type 1 (sCR1)) or the alternative pathway (treatment with heating at 50 degrees C, sCR1, or soluble recombinant CR1 lacking the first of the four long homologous repeat sequences (sCR1[desLHR-A])) inhibited lysis; both pathways were required for lysis of sheep erythrocytes by C2D and C4D guinea pig sera. i.v. injection of anti-Forssman Ab in normal guinea pigs resulted in rapid death from pulmonary shock, whereas C4D guinea pigs had no adverse effect. Surprisingly, C2D guinea pigs either died in a delayed fashion or had a sublethal reaction. sCR1 treatment prevented Forssman shock in both normal and C2D guinea pigs, whereas sCR1[desLHR-A] prevented Forssman shock only in C2D animals. Our results suggest that the C2-bypass pathway occurs in vivo to produce tissue damage. Activation of complement in the absence of C2 appears to be far more efficient than in the absence of C4.
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Wagner E, Platt JL, Howell DN, Marsh HC, Frank MM. IgG and Complement-Mediated Tissue Damage in the Absence of C2: Evidence of a Functionally Active C2-Bypass Pathway in a Guinea Pig Model. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.163.6.3549] [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
In vitro complement-mediated lysis of heavily sensitized sheep erythrocytes by C4-deficient (C4D) guinea pig and C2-deficient (C2D) human sera was demonstrated some years ago. It was postulated that these “complement-bypass” pathways resulted from activation of C1 and components of the alternative pathway. We used normal, C2D, and C4D guinea pigs in a Forssman shock model to test the in vivo relevance of the C2- and C4-bypass pathways of complement activation. High concentrations of both anti-Forssman Ab and C2D or C4D guinea pig serum induced efficient lysis of sheep erythrocytes in vitro. The most efficient lysis was observed when IgG Ab and C2D guinea pig serum were used. Blocking either the classical pathway (treatments with EGTA-Mg2+ or soluble recombinant complement receptor type 1 (sCR1)) or the alternative pathway (treatment with heating at 50°C, sCR1, or soluble recombinant CR1 lacking the first of the four long homologous repeat sequences (sCR1[desLHR-A])) inhibited lysis; both pathways were required for lysis of sheep erythrocytes by C2D and C4D guinea pig sera. i.v. injection of anti-Forssman Ab in normal guinea pigs resulted in rapid death from pulmonary shock, whereas C4D guinea pigs had no adverse effect. Surprisingly, C2D guinea pigs either died in a delayed fashion or had a sublethal reaction. sCR1 treatment prevented Forssman shock in both normal and C2D guinea pigs, whereas sCR1[desLHR-A] prevented Forssman shock only in C2D animals. Our results suggest that the C2-bypass pathway occurs in vivo to produce tissue damage. Activation of complement in the absence of C2 appears to be far more efficient than in the absence of C4.
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Parker W, Lin SS, Yu PB, Sood A, Nakamura YC, Song A, Everett ML, Platt JL. Naturally occurring anti-alpha-galactosyl antibodies: relationship to xenoreactive anti-alpha-galactosyl antibodies. Glycobiology 1999; 9:865-73. [PMID: 10460828 DOI: 10.1093/glycob/9.9.865] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Antibodies produced by an individual without a known history of sensitization to the relevant antigen are called "natural" antibodies. Some natural antibodies, called xenoreactive antibodies, react with the cells of foreign species. Most xenoreactive antibodies in humans and higher primates bind to a nonreducing terminal galactose expressed by pigs and other lower mammals. Although human natural antibodies which bind to one or more of a variety of terminal alpha-galactosyl structures have been identified previously, the antigen recognized by anti-alpha-galactosyl antibodies on the cells of foreign species is thought to be exclusively Galalpha1-3Gal. Thus, anti-alpha-galactosyl antibodies which do not react with Galalpha1-3Gal are thought to be nonxenoreactive. Here, we identify natural antibodies in human serum which bind to Galalpha1-6Hexosepyrranosides but not Galalpha1-3Gal, indicating that these antibodies are not xenoreactive. Various lower mammals were found to have natural anti-Galalpha1-2Gal antibodies in their sera, suggesting that at least some anti-Galalpha1-2Gal antibodies might not be xenoreactive and indicating, surprisingly, that anti-alpha-galactosyl antibodies are much more phylogenetically disperse than previously known. Also surprising was the finding that some natural antibodies which bind to Galalpha1-3Gal in vitro do not bind to porcine xenografts. These studies show that naturally occurring anti-alpha-galactosyl antibodies in mammalian serum include antibodies with a greater variety of reactivities than previously thought, only some of which would bind to a porcine xenograft. Further, these studies show that the methods used to detect anti-alpha-galactosyl antibodies of relevance in xenotransplantation must be carefully evaluated to avoid detection of anti-alpha-galactosyl antibodies which would not bind to a porcine organ and which therefore are not involved in xenograft rejection.
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Itoh-Lindstrom Y, Piskurich JF, Felix NJ, Wang Y, Brickey WJ, Platt JL, Koller BH, Ting JPY. Reduced IL-4-, Lipopolysaccharide-, and IFN-γ-Induced MHC Class II Expression in Mice Lacking Class II Transactivator Due to Targeted Deletion of the GTP-Binding Domain. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.163.5.2425] [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
Class II transactivator (CIITA) is an unusual transcriptional coactivator in that it contains a functionally important, GTP-binding consensus domain. To assess the functional role of the GTP-binding domain of CIITA in vivo, we have generated knockout mice that bear a mutation in the CIITA gene spanning the GTP-binding domain. Upon analysis, these mice show no detectable CIITA mRNA; hence, they represent mice with deleted CIITA rather than mice with defects in the GTP-binding domain only. In these knockout mice, MHC class II expression is nearly eliminated, although a faint RT-PCR signal is visible in spleen, lymph node, and thymus, suggestive of the presence of CIITA-independent regulation of MHC class II expression. Invariant chain expression is also greatly reduced, but to a lesser extent than MHC class II. Serum IgM is not decreased, but the serum IgG level is greatly reduced, further confirming the absence of MHC class II Ag-dependent Ig class switching. Induction of MHC class II expression by IL-4 or LPS was absent on B cells, and Mac-1+ cells showed no detectable induction of MHC class II by either IL-4, LPS, or IFN-γ. These findings demonstrate a requirement for CIITA in IFN-γ-, IL-4-, and endotoxin-induced MHC class II expression as well as the possibility of rare CIITA-independent MHC class II expression.
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Abstract
The complement system contributes critically to the barrier to transplantation of cells and organs. In the case of tissues and organs transplanted between individuals of the same species, that is in allotransplantation, the barrier posed by complement is seemingly eclipsed by the barrier posed by cellular immune responses. In the case of cells and organs transplanted between individuals of disparate species, that is xenotransplantation, the complement system has been thought to pose a nearly insurmountable barrier. With our understanding on how the complement system contributes to rejection, it is now clear that the complement system is more important in allotransplantation and more forgiving in xenotransplantation than was previously thought.
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