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J H Artrip

Publications and source records attributed to J H Artrip.

15 recordsLinked to original sources
PubMed1999

Hemodynamic effects of direct biventricular compression studied in isovolumic and ejecting isolated canine hearts.

BACKGROUND: Biventricular direct cardiac compression (DCC) can potentially support the failing heart without the complications associated with a blood/device interface. The effect of uniform DCC on left and right ventricular performance was evaluated in 7 isolated canine heart preparations. METHODS AND RESULTS: A computer-controlled afterload system either constrained the isolated heart to contract isovolumically or simulated hemodynamic properties of physiological ejection. Biventricular DCC was provided by a chamber surrounding the heart that allowed adjustment of the compression pressure, onset time, and duration. Through a series of ventricular preloads, the effect of DCC on the end-systolic pressure-volume relationship (ESPVR) was evaluated under isovolumic and ejecting conditions. Under both conditions, DCC shifted the ESPVR of the left and right ventricles upward by an amount approximately equal to the compression pressure. The augmentation of end-systolic pressure for each initial preload tested, however, was less under ejecting conditions, because reductions in end-systolic and end-diastolic volumes occurred with ejection. Nevertheless, the net effect was to increase stroke volume. Measurement of M&f1;O2 demonstrated that at a given ventricular volume, M&f1;O2 did not change with DCC; however, peak ventricular pressure increased substantially, so that the effective pressure-volume area increased. CONCLUSIONS: Biventricular DCC can augment end-systolic pressure with no added costs of M&f1;O2. Under ejecting conditions, this augmentation of ventricular contracting ability manifests as increases in stroke volume. Thus, DCC represents a feasible alternative form of ventricular assist, and devices that support the heart in this manner should be further explored.

Animals↗
PubMed1999

Target cell susceptibility to lysis by human natural killer cells is augmented by alpha(1,3)-galactosyltransferase and reduced by alpha(1, 2)-fucosyltransferase.

Susceptibility of porcine endothelial cells to human natural killer (NK) cell lysis was found to reflect surface expression of ligands containing Gal alpha(1,3)Gal beta(1,4)GlcNAc [corrected], the principal antigen on porcine endothelium recognized by xenoreactive human antibodies. Genetically modifying expression of this epitope on porcine endothelium by transfection with the alpha(1,2)-fucosyltransferase gene reduced susceptibility to human NK lysis. These results indicate that surface carbohydrate remodeling profoundly affects target cell susceptibility to NK lysis, and suggest that successful transgenic strategies to limit xenograft rejection by NK cells and xenoreactive antibodies will need to incorporate carbohydrate remodeling.

Animals↗
PubMed1999

Induction of swine major histocompatibility complex class I molecules on porcine endothelium by tumor necrosis factor-alpha reduces lysis by human natural killer cells.

BACKGROUND: Natural killer (NK) cells have been implicated in a process of delayed xenograft rejection occurring in pig-to-primate organ transplants. As tumor necrosis factor-a (TNF-a) induces expression of both adhesion receptors and major histocompatibility complex class I molecules on porcine endothelium, we investigated the effects of TNF-alpha on human NK cell adherence to and cytotoxicity of porcine aortic endothelial cell (PAEC) monolayers. METHODS: Adherence of human NK cells was measured after PAEC treatment with increasing concentrations of TNF-alpha. Monoclonal antibodies (mAbs) against adhesion molecules on NK cells and PAEC were used in inhibition studies. Resting or TNF-alpha-treated PAEC were used as targets for NK lysis. Increasing titers of anti-swine leukocyte antigen (SLA) class I antibodies or pooled human immune globulin (IVIg) were used to reverse the effects of TNF-alpha on NK lysis. RESULTS: NK cell adhesion to TNF-a-treated PAEC increased in a dose-dependent manner by a maximum of 44%, and was inhibited by mAbs against CD49d, CD11a, CD11b, CD18, and CD2, as well as porcine vascular cell adhesion molecules. In contrast, TNF-alpha treatment of PAEC reduced human NK lysis in a dose-dependent manner. Preincubation of TNF-a-treated PAEC with increasing concentrations of anti-SLA class I mAb increased NK lysis in a titer-dependent manner, and reversed the protective effect on human NK lysis by 77%. Treatment with IVIg, containing antibodies against an a-helical region of HLA class I molecules, had a similar effect. CONCLUSIONS: These results imply that SLA class I molecules can bind to inhibitory receptors on human NK cells, and that these interactions can be augmented by increasing the level of SLA class I molecule expression on porcine endothelium. Strategies that can increase porcine endothelial cell expression of either swine or human major histocompatibility complex class I molecules may reduce human NK activity against porcine xenografts.

Animals↗
PubMed1999

High-level porcine endothelial cell expression of alpha(1,2)-fucosyltransferase reduces human monocyte adhesion and activation.

BACKGROUND: Monocyte binding to and activation by human endothelium requires a number of interactions, including those involving sialylated endothelial cell ligands. As porcine endothelial cell transfection with alpha(1,2)-fucosyltransferase has been shown to reduce terminal sialylation, we investigated whether high-level expression of alpha(1,2)-fucosyltransferase by porcine endothelium would reduce human monocyte adhesion and functional activation. METHOD: Purified human monocytes were labeled with 51Cr, and measured for adherence to human or porcine endothelial cell monolayers in the presence of either medium or monoclonal antibodies against monocyte lectins or sialylated endothelial cell ligands. Monocyte production of prostaglandin E2 (PGE2) and interleukin-1beta (IL-1beta) was measured by enzyme-linked immunosorbent assay, using supernatants collected from cultures performed between human monocytes and human or porcine endothelial cell monolayers. Finally, monocyte adhesion and activation were measured after culture with a porcine endothelial cell line transfected with alpha(1,2)-fucosyltransferase, expressing reduced surface expression of terminal Gal alpha(1,3)-Gal and sialic acid residues. RESULTS: Human monocytes adhered by 50% higher levels to porcine endothelium than to human endothelium. This increased level of adherence was associated with augmented monocyte activation, as defined by 3.3-fold higher levels of PGE2 production and 7.3-fold higher levels of IL-1beta production. Monoclonal antibodies against CD62L (L-selectin) on monocytes or CD15s (sialylated Lewis X) on porcine endothelium reduced monocyte adhesion by 38% and 52%, respectively. Porcine endothelial cell transfection with alpha(1,2)-fucosyltransferase reduced terminal sialic acid expression by 65%, monocyte adherence by 50%, and the production of PGE2 and IL-1beta by 67% and 38%, respectively. CONCLUSIONS: Together, these results demonstrate that human monocytes use surface lectins to bind to sialylated carbohydrate structures on porcine endothelium, and indicate that reduction in porcine endothelial cell surface expression of terminally sialylated structures by high-level alpha(1,2)-fucosyltransferase activity reduces monocyte adherence and activation.

Animals↗
PubMed1998

Preformed IgG antibodies against major histocompatibility complex class II antigens are major risk factors for high-grade cellular rejection in recipients of heart transplantation.

BACKGROUND: Preformed anti-HLA antibodies reacting specifically with donor lymphocytes have been associated with acute vascular rejection and early cardiac allograft failure. However, the effect of preformed anti-HLA antibodies directed against allogeneic major histocompatibility complex (MHC) class I or II antigens of a donor panel on heart transplantation outcome has not been extensively studied. METHODS AND RESULTS: The study group consisted of 68 patients who received cardiac transplants between 1989 and 1996 and who were at high risk for developing anti-HLA antibodies before transplantation. The effect of preformed antibodies against allogeneic MHC class I or class II antigens on the development of early high-grade cellular rejection and on cumulative annual rejection frequency was determined. Both patients with left ventricular assist devices and retransplantation candidates had a similar increase in the frequency of IgG anti-MHC class II antibodies (IgG anti-II) compared with control subjects (P<0.0001), whereas the frequency of IgG anti-MHC class I antibodies (IgG anti-I) was elevated only in patients with left ventricular assist devices. Pretransplantation IgG anti-II predicted early development of high-grade cellular rejection (P=0.006) and higher cumulative annual rejection frequency (P<0.001) in both of these sensitized patient groups. Among retransplantation recipients, a match between donors 1 and 2 at HLA-A additionally predicted an earlier time to a high-grade cellular rejection. CONCLUSIONS: These results emphasize the importance of specifically screening heart transplantation candidates for the presence of IgG antibodies directed against MHC class II molecules and suggest that strategies aimed at their reduction may have an impact on the onset and frequency of high-grade cellular rejections after transplantation.

Adolescent↗
PubMed1998

Induction of tolerance in rodent cardiac allotransplantation using an MHC class I-derived peptide and cyclosporin A.

BACKGROUND: The synthetic peptide corresponding to residues 75-84 of the human major histocompatibility complex class I molecule HLA-B7 (Allotrap 07) has been shown to inhibit differentiation of cytotoxic T lymphocyte precursors. Subsequent treatment of LEW-1A rats with this peptide was associated with a reduction in the level of cytotoxic activity directed to donor alloantigens. This study was undertaken to investigate the effect of Allotrap 07 on rodent heart allograft survival in LEW-1A recipients. METHODS: Heart allografts from Lewis rats were heterotopically transplanted into the infrarenal abdominal aorta of ACI recipients. The treatment groups consisted of different regimens of short-term intravenous Allotrap 07 and oral cyclosporin A. All grafts were palpated daily, with rejection defined as the cessation of palpable contractions. RESULTS: Cardiac allografts transplanted from Lewis to ACI rats survived indefinitely after administration of intravenous Allotrap 07 and oral cyclosporin A. Tolerance induction was donor-specific because third-party Brown-Norway, but not Lewis, grafts were rapidly rejected after implantation into ACI recipients. CONCLUSIONS: Because donor-specific tolerance persisted long after cessation of peptide administration and did not occur when cyclosporin A was omitted from the immunosuppressive regimen, the mechanism may involve induction of clonal anergy.

Administration, Oral↗
PubMed1998

Triple immunosuppression reduces mononuclear cell infiltration and prolongs graft life in pig-to-newborn baboon cardiac xenotransplantation.

OBJECTIVE: Pig hearts transplanted into unmedicated newborn baboons do not undergo hyperacute rejection by preformed xenoantibody and complement. These grafts are rejected at days 3 to 4 in association with the infiltration of macrophages and natural killer cells. We investigated whether an immunosuppressive regimen used widely in cardiac allotransplantation could reduce this cellular response and prolong xenograft life. METHODS: Ten newborn baboons underwent heterotopic pig cardiac xenotransplantation. Five baboons were immunosuppressed with mycophenolate mofetil (100 mg/kg), methylprednisolone acetate (0.8 mg/kg), and cyclosporine A (INN: ciclosporin; 10 mg/kg). Xenograft rejection was studied by light microscopy and immunofluorescence. The induced humoral response to porcine xenoantigens was documented by enzyme-linked immunosorbent assay using synthetic alpha-1,3-galactosyl epitopes coupled to bovine serum albumin. RESULTS: Graft life was extended from a mean of 3.6 +/- 0.5 days (n = 5) to a mean of 6.2 +/- 1.1 days (n = 5, p = 0.01). In comparison with controls, explanted grafts from medicated baboons demonstrated reduced infiltration with natural killer cells and macrophages, but increased evidence of complement-mediated rejection substantiated by increased deposition of immunoglobulin M, complement, and fibrin. In all baboons receiving transplants, levels of both immunoglobulin M and immunoglobulin G anti-galactose were significantly increased after transplantation, with immunoglobulin G levels remaining persistently elevated. CONCLUSIONS: These results indicate that cyclosporine-based triple immunosuppression marginally prolonged xenograft survival and appears to have reduced the natural killer cell and macrophage infiltrates. The immunosuppressive protocol, however, was not adequate to prevent the induced immunoglobulin M humoral response and prevent complement-mediated graft injury.

Animals↗
PubMed1998

Role of natural killer cells, macrophages, and accessory molecule interactions in the rejection of pig-to-primate xenografts beyond the hyperacute period.

Pig-to-primate cardiac xenografts surviving beyond the period of hyperacute rejection succumb after 3-4 days to a secondary immunologic response characterized by xenograft infiltration with NK cells and macrophages. Circulating baboon mononuclear cells contain NK cell precursors which mediate lysis of porcine endothelium by two distinct mechanisms: antibody-dependent cellular cytotoxicity and lymphokine activation. IL-2 activated NK lysis of porcine endothelium was 2.4-fold stronger than lysis occurring following engagement of FcRIII by xenoreactive IgG. IL-2 augmented NK lysis involved interactions between CD2 and CD49d on baboon NK cells and their respective ligands on porcine endothelium, since NK lysis was reduced either by using Mabs against CD2, CD49d, or porcine VCAM, or by treating endothelial cells with PIPLC to cleave GPI-linked molecules. These results imply that interactions between accessory molecule receptor-ligand pairs on primate NK cells, macrophages and porcine endothelium are of critical importance in delayed xenograft rejection.

Animals↗
PubMed1998

Importance of CD49d-VCAM interactions in human monocyte adhesion to porcine endothelium.

By using a primate model of natural antibody depletion, we have previously shown that delayed rejection of porcine cardiac xenografts in unmodified primate recipients resulted from xenograft infiltration with monocyte/macrophage lineage cells. In the present study, we initially showed that human monocytes/macrophages demonstrated significantly greater adherence to unstimulated pig aortic endothelial cells (PAEC) than to human umbilical vein endothelial cells (HUVEC). Human TNF-alpha augmented monocyte adhesion to HUVEC by 5-fold higher levels than to PAEC. This effect could not be explained on the basis of incompatibility between human TNF-alpha and its receptor on PAEC since porcine VCAM expression increased by 75-85% after stimulation with TNF-alpha. TNF-augmented monocyte adherence was abrogated by either treatment of PAEC with an anti-VCAM Mab or monocytes with an anti-CD49d Mab. These results suggest that VCAM-CD49d interactions are important in adhesion of human monocytes to PAEC but may not be as effective as those between human monocytes and allogeneic endothelium, perhaps because of structural differences across species. Other interactions, as yet undefined, must explain the relative increase in adhesiveness of human monocytes for unstimulated PAEC versus HUVEC. In experiments investigating the functional consequences of this enhanced monocyte adherence, PAEC stimulation induced 10-fold higher levels of macrophage-derived IL-1 beta and 3-fold higher levels of T cell proliferation compared with HUVEC. Using an anti-DR Mab to interrupt antigen presentation by autologous macrophages markedly reduced the T cell proliferative response to PAEC. Together, these results indicate that the enhanced adherence of human monocytes to PAEC contributes to xenograft rejection beyond the hyperacute period by leading to tissue infiltration, elaboration of cytokines, and an augmented indirect pathway of T cell xenoantigen recognition.

Animals↗
PubMed1997

Cardiac xenotransplantation.

The severe shortage of human donor hearts has prompted several investigators to develop alternative strategies using cross-specie organs or xenografts. Unlike human allotransplantation, in which the important antigenic differences between donor and recipient are confined to the major histocompatibility and blood group antigens, xenotransplantation is confronted with the potential for multiple antigenic differences. In the pig-to-primate model of xenotransplantation, the primary obstacle to cross-species transplantation has been hyperacute rejection mediated by complement fixing antibodies directed against galactose alpha 1,3-galactose (Gal alpha 1,3-Gal) epitopes on the pig endothelium. Conventional immunosuppression is unable to overcome hyperacute rejection; however, recent efforts in molecular biology have focused on genetically engineering porcine donors to express human proteins in their tissue. Transgenic pigs that express human complement regulatory proteins on their endothelium have been developed. Heterotopic transplantation of these transgenic donor hearts have had only moderate success. Alternative approaches attempt to eliminate the Gal alpha 1,3-Gal epitopes by genetically "knocking out" the enzyme necessary for its synthesis, or to reduce the expression of Gal alpha 1,3-Gal epitopes by genetically inserting enzymes that redirect precursor molecules into alternative synthetic pathways. The technology to knock out the necessary enzymes in pigs is not yet available; however, pigs expressing the H-transferase gene have been developed and show reduced levels of Gal alpha 1,3-Gal epitopes. Although this "new breed" of transgenic pigs may overcome the barrier of hyperacute rejection, special strategies will need to be developed that target the next barrier of xenograft rejection.

Animals↗
PubMed1997

Lysis of pig endothelium by IL-2 activated human natural killer cells is inhibited by swine and human major histocompatibility complex (MHC) class I gene products.

We have previously described a form of xenograft rejection, mediated by natural killer (NK) cells, occurring in pig-to-primate organ transplants beyond the period of antibody-mediated hyperacute rejection. In this study, two distinct NK activation pathways were identified as mechanisms of pig aortic endotheliual cell (PAEC) lysis by human NK cells. Using an antibody-dependent cellular cytotoxicity (ADCC) assay, a progressive increase in human NK lysis of PAEC was observed following incubation with human IgG at increasing serum titer. In the absence of IgG, a second mechanism of PAEC lysis by human NK cells was observed following activation with IL-2. IL-2 activation of human NK cells increased lysis of PAEC by over 3-fold compared with ADCC. These results indicate that IL-2 activation of human NK cells induces significantly higher levels of lytic activity than does conventional ADCC involving IgG and FcRIII. We next investigated the role of MHC class I molecules in the regulation of NK lysis following IL-2 activation. PAEC expression of SLA class I molecules was increased by up to 75% by treatment with human TNFa. Following treatment with TNFa at 1 u/ml, IL-2 activated human NK lysis of PAEC was inhibited at every effector:target (E:T) ratio tested. Maximal effect occurred at an E:T ratio of 10:1, with TNFa inhibiting specific lysis by 59% (p < 0.01). Incubation with an anti-SLA class I Mab, but not IgG isotype control, abrogated the protective effects of TNFa on NK lysis of PAEC, suggesting direct inhibitory effects of SLA class I molecules on human NK function. To investigate whether human MHC class I molecules might have similar effects on human NK lysis of PAEC, further experiments were performed using a soluble peptide derived from the alpha-helical region of HLA-B7. Incubation with the HLA-B7 derived peptide significantly reduced the IL-2 activated NK lytic activity against PAEC in a dose-dependent fashion. Maximal effect occurred at a concentration of 10 mg/ml, where an 8-fold reduction in IL-2 augmented NK lysis was observed (p < 0.01). These results suggest that IL-2 activated human NK lysis of porcine xenografts may be inhibited by strategies which increase PAEC expression of SLA class I molecules, introduce HLA class I genes into PAEC, or use soluble HLA class I peptides.

Animals↗
PubMed1997

Human NK cells demonstrate increased adherence and lysis of porcine endothelium following activation with IL-2.

BACKGROUND: For clinical xenotransplantation of pig organs to be successful, the significant barriers of host cellular immunity against the pig will need to be overcome. Natural killer (NK) cells appear to play an important role in rejection of discordant xenografts, and IL-2 activated human NK cells are cytotoxic to human endothelium. We addressed the role of IL-2 activated human and baboon NK cells in the primate immune response to pig xenoantigens in vivo and in vitro. METHODS: Human natural killer (NK) cells were isolated from pooled human peripheral mononuclear cells (PBMC) using density gradient centrifugation method. Phenotype of isolated cells was confirmed by flow cytometry. Purified NK cells were than tasted for spontaneous and IL-2 augmented adhesion and lysis of cultured pig aortic endothelial cells (PAEC) monolayers in a short-term 51 Cr-release assay. The effects of human macrophage derived cytokines TNF alpha and IL-1 on adhesion of IL-2 activated NK cells were studied. RESULTS: Human NK cells demonstrate prominent adherent and lytic activity against pig endothelium, which can be significantly augmented by IL-2. Macrophage derived cytokines can further augment the adherent properties of these NK cells. CONCLUSIONS: These result suggest that human NK cells are likely to play a significant role in rejection of pig-to-human xenografts.

Animals↗
PubMedDate not supplied

Immature host for xenotransplantation.

The overall shortage of appropriate donor organs has prompted transplant physicians and surgeons to consider using organs from other nonhuman species. The shortage of appropriate human donor hearts for newborn recipients is especially severe. Presently, the pig appears to be the most appropriate source for organs. Humans and baboons uniformly develop high titers of complement-fixing (IgM) anti-pig xenoantibodies, resulting in complement-mediated hyperacute rejection (HAR) of pig organs transplanted into mature baboons within minutes to hours. In contrast, newborn humans and baboons do not have high titers of anti-pig IgM xenoantibody, and consequently pig cardiac xenografts transplanted into newborn baboons do not undergo HAR. Rather, these organs are rejected at days 3 to 4 by a distinctive immunologic process that involves natural killer cells and macrophages. With the addition of cyclosporine-based triple immunosuppression, this process is reduced and graft life is prolonged to 6 to 7 days. This therapy, however, is not sufficient to prevent the induced humoral response to the graft, and the organs are rejected by antibody- and complement-dependent mechanisms. Future treatment strategies to reduce this humoral response must incorporate immunodepletion columns, soluble complement-inhibiting agents, and additional anti-B lymphocyte agents. These strategies, in conjunction with the use of transgenic pig organs that express human membrane-bound complement regulatory proteins or reduced xenoantigenic epitopes could further prolong graft life. Clinical trials are being formulated that would utilize pig organs as a "bridge," sustaining a newborn human in need of a heart transplant until an appropriate donor is located.

Animals↗