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Biomedical subjects

G Proud

Publications and source records attributed to G Proud.

At least 37 records · Page 2Linked to original sources
PubMed1995

Renal allograft rejection: the temporal relationship and predictive value of plasma TNF (alpha and beta), IFN-gamma and soluble ICAM-1.

Recently, close interactions have been described between the tumour necrosis factors alpha and beta (TNF-alpha and beta), interferon-gamma (INF-gamma) and intercellular adhesion molecule-1 (ICAM-1) in T-cell mediated immune activation. During the process of renal graft rejection, the properties of these cytokines to act as powerful stimulators of macrophages, to upregulate class II MHC expression and to stabilise cell-to-cell binding make them of great potential interest. The aim of the present study was to determine the plasma levels of each cytokine and soluble ICAM-1 in 16 renal allograft recipients. We examined plasmas of patients for the first 2 weeks after transplantation and correlated results with the clinical pattern of rejection. Our data suggest an immunopathologic involvement of TNF-alpha, TNF-beta and slCAM-1 in renal allograft rejection and showed that there was a significant elevation in plasma concentrations of these parameters 2 or 3 days prior to the diagnosis of clinical rejection. Rises in INF-gamma did not appear to be significant with regard to rejection as very high levels were found in patients showing no evidence of clinical rejection.

Enzyme-Linked Immunosorbent Assay↗
PubMed1995

Flow cytometric crossmatching in renal transplantation--the long-term outcome.

The association of a positive flow cytometric crossmatch between recipient IgG directed against donor T lymphocytes and poor outcome is well described in renal transplantation. Until now no long-term follow-up on such patients has been available. In this study, 117 renal transplant patients were followed up for a period of 5 years. Of these 21 were known to have donor T cell directed IgG and five had B lymphocyte directed IgG. Both groups of patients with these antibodies had a significantly poorer outcome at 5 years than did the group of patients without IgG (p < 0.0001, Handel Maenzel test). Patients with antibody detected preoperatively were tested again either at the time of graft failure or at 5 years post-transplantation. The sera were tested against stored donor cells and the intensity of surface IgG compared with the preoperative levels. In those recipients who lost their grafts the levels increased in 60% of cases, but those who retained their grafts also had an increase in levels of donor directed antibody in 50% of cases. The changing levels of antibody therefore appeared to have little relevance to outcome. However when IgG isotypes were considered, in those who experienced graft failure and also had a gamma 3 isotype, a rise in IgG was demonstrated in all cases. Conversely, successful grafts with gamma 3 had a decline in levels between preoperative and 5-year samples in three of the four cases (not significant).

Flow Cytometry↗
PubMed1994

Characterization of donor-directed antibody class in the post-transplant period using flow cytometry in renal transplantation.

Over the past few years there has been increasing awareness of the importance of humoral mechanisms in the rejection of renal transplants. In this study we have monitored the development of antibodies directed against donor T and B lymphocytes using the sensitive flow cytometric technique. Forty-two cadaveric renal transplants were studied both before and for a maximum of 14 days after transplantation. Donor cells were separated from spleen on the day of transplantation and stored in liquid nitrogen until required. The dual colour flow cytometric assay was used to detect IgG or IgM directed against donor T or B lymphocytes. Using AB sera as controls, results were expressed as relative median fluorescence (RMF) and then correlated with the clinical performance of the grafts. Significant associations were found between the incidence of donor-directed antibodies and the development of clinical rejection. The magnitude of the rise in antibody levels was also related to graft performance. In patients showing severe graft rejection, high levels of antibodies of the IgG class developed before the clinical diagnosis of rejection was made. The routine use of this test allows the prediction of impending severe rejection to be made and may have important implications for immunosuppressive therapy.

B-Lymphocytes↗
PubMed1994

Xenotransplantation: an examination of the adhesive interactions between human lymphocytes and porcine renal epithelial cells.

Specific adhesion molecules stabilize the binding between lymphocytes and antigen bearing cells; this intercellular adhesion is vital to both the affector and effector phases of an immune response. It is not known whether adhesion molecules and their counter-receptors can form the cross-species interactions that will facilitate human T cell recognition of xenogeneic porcine target cells. In this report it is demonstrated that a higher proportion of mitogen-activated than of resting human lymphocytes adhere to cultured porcine renal epithelial cells. Furthermore, antibody blocking experiments demonstrated that at least part of this cell-cell binding is stabilized by the human adhesion molecules LFA-1 (lymphocyte function-associated antigen-1) and the alpha 4-containing integrins. It is possible that this capacity for cross-species adhesion will play a role during the cell-mediated rejection of clinical porcine xenografts.

Animals↗
PubMed1994

T-cell anergy: a consequence of interaction between T cells and allogeneic rat renal epithelial cells.

In order to study the immunogenicity of parenchymal cells within an allograft, renal tubular cells were propagated from both PVG and DA strain rats. These cells were induced to express class II major histocompatibility (MHC) antigens by stimulation for 4 days with interferon-gamma (IFN-gamma). It was found that resting lymphoid cells derived from Lewis rats responded vigorously after stimulation with irradiated splenic cells from PVG rats. However, stimulation with renal cells from PVG rats did not result in interleukin (IL-2) production or lymphoproliferation. Furthermore, lymphocytes from this mixture failed to respond to secondary stimulation by PVG splenic cells; lymphocytes primed by mixture with DA renal cells responded normally to secondary stimulation by PVG splenic cells. These results indicate that renal epithelial cells can specifically anergise allogeneic lymphocytes.

Animals↗
PubMed1994

Urological complications following renal transplantation. A study of 1016 consecutive transplants from a single centre.

A total of 1016 consecutive renal transplants performed between 1976 and 1990 were analysed retrospectively to determine the incidence of urological complications and possible predisposing factors. Some 189 episodes of ureteric obstruction and/or urinary leak occurred in 143 patients (overall incidence 14.1%). The median annual rate of urinary leak was 5.1%; that of ureteric obstruction was 4.5% pre-1986 and 16.1% post-1986. Sixty-three episodes of urinary leak occurred in 54 patients from 1 day to 3 months post-transplant and 60% involved the distal ureter. Thirty were treated primarily by reconstructive surgery, ten required nephrectomy and three died of associated sepsis. A total of 126 episodes of ureteric obstruction occurred in 104 patients from 1 day to 12 years post-transplant and 86% involved the distal ureter. Prior to 1986, 10/11 patients with ureteric obstruction were treated by reconstructive surgery, but since then 88 (95%) have been treated by percutaneous nephrostomy, with or without stenting, with only one graft lost and no deaths. Children had a significantly increased incidence of ureteric obstruction (P < 0.001) whilst male recipients had an increased incidence of urinary leak (P = 0.04). More patients with ureteric obstruction than those without had two or more episodes of rejection (P = 0.03). No single cause for the increased incidence of ureteric obstruction since 1986 has been identified. Continued attention to technical detail and further study of this trend is warranted.

Adolescent↗
PubMed1993

Administration of ATG according to the absolute T lymphocyte count during therapy for steroid-resistant rejection.

In renal transplantation, treatment of steroid-resistant rejection (SRR) with antithymocyte globulin (ATG) has been widely reported but over-immunosuppression remains a common problem. In the first ten patients (group 1) treated for SRR with rabbit ATG, three developed serious viral infections and two deaths occurred due to CMV pneumonitis. ATG was only omitted if thrombocytopenia or neutropenia occurred. In the next 17 patients (group 2) with SRR, ATG was administered according to the absolute T lymphocyte count. T lymphocytes were measured by flow cytometric analysis of CD3-labelled lymphocytes. ATG dosage was adjusted on a daily basis to keep the absolute T lymphocyte count under 50 cells/microliters. Administration of ATG according to the absolute T lymphocyte count resulted in a significant reduction in the mean dose of ATG given to the group 2 patients (P < 0.001). A significant decrease in the incidence of serious viral infections (P = 0.04) was achieved without reducing the ability of ATG to reverse the SRR (P = 0.29) or increasing the number of grafts lost at 1 year in the group 2 patients (P = 0.23).

Adult↗
PubMed1993

Renal allograft rejection: examination of adhesion blockade by antilymphocyte antibody drugs.

An assay was developed to investigate the binding of lymphocytes to cultured human renal epithelial cells. This binding was increased following lymphocyte activation by culture either with a polyclonal mitogen or with allogeneic stimulator cells. It was shown that such activation increased lymphocyte expression of the adhesion molecules CD2, LFA-1, and VLA-4. The ligand for each of these molecules was demonstrated on the surface of cultured renal epithelial cells. Polyclonal antilymphocyte antibody (ALA) preparations are used frequently to reverse intractable episodes of acute renal allograft rejection. It was demonstrated that such agents reduce the binding of activated lymphocytes to renal epithelial cells and subsequent cell lysis with a similar dose-response curve. Application of this assay may allow improved evaluation and titration of therapeutic antibody preparations. A range of monoclonal antibodies specific for components of the three adhesion molecule systems investigated in this work were added to lymphoid cell binding assays. It was found that combinations of these antibodies designed to interfere simultaneously with each of these adhesion interactions inhibited binding less well than the ALA preparation. It is likely that the superior inhibition of binding produced by ALA is due to the polyclonality of the antibodies which can block multiple epitopes on a wide range of potential adhesion molecules.

Antibodies, Monoclonal↗
PubMed1993

Renal allograft rejection: expression and function of VCAM-1 on tubular epithelial cells.

The interaction between vascular cell adhesion molecule-1 (VCAM-1) and very late antigen-4 (VLA-4) is known to play an important role in stabilizing the adhesion of lymphocytes to endothelial cells. Such cellular adhesion is crucial to many immunological processes including lymphocyte-mediated cell lysis. In this study the expression of VCAM-1 on renal tubular epithelial cells is demonstrated on biopsy sections recovered during acute renal allograft rejection. Experiments performed using epithelial cells cultured from renal tubules show that VCAM-1 is up-regulated by addition of the inflammatory cytokines tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). Combination of TNF-alpha and IFN-gamma synergized to induce high levels of VCAM-1 expression. Further experiments demonstrated that the cytokines produced by activated lymphocytes in mixed leucocyte culture also up-regulate expression of VCAM-1. Assays of the adhesion of lymphoid cells to cultured renal epithelial cells showed that cytokine pretreatment of the renal cells enhanced the binding of lymphoid cells. The proportion of bound lymphoid cells was significantly reduced by addition of an antibody capable of blocking the interaction of VCAM-1 with VLA-4. This result indicated that the VCAM-1 induced on renal epithelial cells by inflammatory cytokines is functionally capable of binding VLA-4, thereby enhancing the adhesion of potentially graft-damaging lymphoid cells.

Cell Adhesion↗
PubMed1993

Experimental renal transplantation: IgG antibodies which bind to graft tubular epithelial cells cannot be detected in the serum of recipient rats after pre-operative transfusion of donor blood.

Transfusion of donor blood 7 days prior to renal transplantation between certain rat strain combinations can delay subsequent graft rejection. The mechanism responsible for this increased graft tolerance remains largely unclear. In this paper it is demonstrated that IgG antibodies with affinity for cultured donor renal epithelial cells develop in the plasma of recipient PVG rats within 7 days of transplantation of a DA rat kidney. These IgG antibodies are not specific for kidney cell-restricted antigens as the activity can be completely absorbed using cells which express donor class-I MHC antigens. However, the IgG may contribute to the acute rejection of graft cells by activating antibody-dependent cell-mediated cytolytic (ADCC) mechanisms. Transfusion of donor blood 7 days prior to renal transplantation between DA and PVG rats prevented the development of IgG antibodies which bind to resting or cytokine-activated donor renal epithelial cells. Serum taken 7 days after the transplantation of animals which had been previously transfused with donor blood was not able to activate ADCC mechanisms of donor cells. The donor blood transfusion-mediated abrogation of IgG binding to graft cells may delay the onset of graft rejection by preventing antibody-dependent graft cell lysis.

Animals↗
PubMed1993

Interaction between T lymphocytes and kidney epithelial cells during renal allograft rejection.

Cultured human renal epithelial cells were treated with the cytokines IFN-gamma and TNF-alpha and alteration in expression and function of markers including Classes I and II MHC antigens and the adhesion molecules LFA-3 and ICAM-1 was examined. It was found that a mixture of IFN-gamma and TNF-alpha induced Class II MHC antigens, up-regulated expression of Class I, LFA-3 and ICAM-1 molecules and enhanced binding of 51Cr-labeled mononuclear immune cells. However, lymphocytes failed to proliferate in response to allo-stimulation by renal epithelial cells. Lymphocytes recovered after four days in mixed culture with allogeneic renal cells were purified and re-stimulated with irradiated spleen cells for five days prior to measurement of proliferation. These lymphocytes failed to proliferate if the spleen cells were syngeneic with the renal cells used in the primary stimulation. However, if the renal cells were from a third-party donor the lymphocytes showed a normal proliferative response to the allogeneic spleen cells. It has been demonstrated that cytokine-stimulated renal epithelial cells bind, but fail to initiate proliferation of, resting allogenic lymphocytes and that activated renal cells can specifically anergise potentially graft damaging allospecific T lymphocytes.

Antigens, CD↗
PubMed1993

Renal allograft rejection: protection of renal epithelium from natural killer cells by cytokine-induced up-regulation of class I major histocompatibility antigens.

The potential of natural killer (NK) cells to contribute to renal allograft rejection was modelled by mixing NK cells with cultured renal epithelial cells. It was found that the renal cells were readily lysed by cytokine-activated NK cells. Renal cells which were previously stimulated by culture with either interferon-gamma (IFN-gamma) or supernatant from mixed leucocyte cultures (MLC) were relatively resistant to such lysis; stimulation with tumour necrosis factor-alpha (TNF-alpha) had no effect. None of these cytokine preparations had any effect on the lysis of renal cells by either specific cytotoxic T lymphocytes or the antibody-dependent cell-mediated cytotoxic mechanism. The expression of class I major histocompatibility complex (MHC) antigens was up-regulated by stimulation of renal cells with either IFN-gamma or MLC supernatant; treatment with TNF-alpha had no effect on the expression of these antigens. Protection from NK cell-mediated lysis appeared to correlate with the expression of class I MHC antigens by the renal cells. Artificial removal of these MHC antigens by treatment with citric acid significantly increased the susceptibility of cytokine-stimulated renal cells to lysis by activated NK cells. This increase was not caused by enhanced binding of NK cells to acid-treated renal cell targets. These results suggest that high levels of class I MHC antigen expression block NK cell triggering after engagement with renal epithelial cells. It is concluded that cytokines present within the renal microenvironment during rejection protect graft cells from lysis by NK cells by causing local upregulation of the expression of class I MHC molecules.

Antibody-Dependent Cell Cytotoxicity↗