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Biomedical subjects

G Proud

Publications and source records attributed to G Proud.

At least 19 recordsLinked to original sources
PubMed1996

Insulin-stimulated phosphorylation of initiation factor 4E is mediated by the MAP kinase pathway.

The cap-binding initiation factor 4E (eIF4E) is regulated by phosphorylation and by the inhibitory binding protein 4E-BP1. Here we show that insulin-induced phosphorylation of eIF4E is not significantly affected by rapamycin, but is sensitive to wortmannin, which inhibits phosphatidylinositol 3'-kinase and blocks the activation of MAP kinase. Since PD098059, an inhibitor of MAP kinase activation, also blocks insulin-induced phosphorylation of eIF4E, the MAP kinase pathway seems to mediate this effect. Phosphorylated eIF4E can still bind to 4E-BP1. These data illustrate that (i) distinct signalling pathways mediate the phosphorylation of eIF4E and 4E-BP1 and (ii) phosphorylation of eIF4E, unlike that of 4E-BP1, does not lead directly to the release of 4E-BP1.

Androstadienes↗
PubMed1996

Flow cytometric crossmatching in renal transplantation--outcome after five years.

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. A total of 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 5 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 posttransplantation. 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 that 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, for 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 (p not significant).

Flow Cytometry↗
PubMed1995

The value of posttransplant monitoring of interleukin (IL)-2, IL-3, IL-4, IL-6, IL-8, and soluble CD23 in the plasma of renal allograft recipients.

Over the past few years, the central role of cytokines in the amplification of the immune response has been reported and several studies have examined the relationship between the plasma level of individual lymphokines during renal allograft rejection. The aim of the present investigation was to study simultaneously IL-2, IL-3, IL-4, IL-6, IL-8, and soluble CD23. Analysis of results has allowed both the prognostic value and any possible interrelationships between the measured cytokines to be determined. We studied 16 renal transplant recipients for the first 14 days after transplantation. Seven patients showed clinical evidence of acute allograft rejection and 5 showed excellent stable graft function with no signs of rejection. Primary nonfunction was seen in 4 patients. The plasma levels of each cytokine were measured by commercially available ELISA and immunoradiometric assay kits. As reported in previous studies, plasma IL-2 levels, whenever found at detectable levels, were predictive of impending graft rejection. Serial monitoring of IL-4 and IL-6 was more reliable for the differential diagnosis of rejection, particularly toward the end of the first week after transplantation. IL-3, IL-8, and soluble CD23 were not diagnostic or predictive of rejection, due to the occurrence of significantly high levels in transplant patients who showed no evidence of clinical rejection. While the value of cytokine monitoring has been shown in this study, it should be remembered that infection, although not seen in these studies, may have a profound affect on the results obtained.

Biomarkers↗
PubMed1995

Renal allograft rejection. Tubular epithelial cells present alloantigen in the presence of costimulatory CD28 antibody.

Renal tubular epithelial cells can be induced to express potentially immunogenic levels of class II MHC antigens but fail to stimulate the activation of allospecific T lymphocytes. The current series of experiments was performed to determine whether the failure of lymphocyte activation in this system is caused by defective T cell costimulation. It was found that cultured renal epithelial cells expressed class II MHC antigens and the immunoregulatory adhesion molecules intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and lymphocyte function-associated antigen-3 after stimulation with IFN-gamma, but that the B7 ligand for CD28 was not expressed. Mixed cell culture experiments were set up in which lymphocytes were mixed with IFN-gamma-treated allogeneic renal cells. Lymphoproliferation and IL-2 production were only observed if bivalent anti-CD28 antibodies were titrated into these cultures. The requirement for antigen stimulation was retained by these lymphocytes, as no proliferation was observed after stimulation by class II MHC antigen nonexpressing, resting renal cells. Further experiments demonstrated that the effectiveness of the anti-CD28 antibody-mediated signal was enhanced by cross-linking with a secondary anti-kappa-chain antibody. These data are consistent with the concept that a costimulatory signal generated by ligation of CD28 is of central importance to the development of an immune response to alloantigen. Furthermore, these results indicate that tubular epithelial cells within a rejecting renal allograft are unlikely to initiate direct activation of infiltrating allospecific lymphocytes.

Antibodies, Monoclonal↗
PubMed1995

The clinical significance of post-transplantation non-HLA antibodies in renal transplantation.

This study was undertaken to examine the clinical relevance of antibodies detected in the sera of patients following renal transplantation. The sera from 23 transplant recipients with acute rejection and 10 transplant recipients with diagnosed chronic rejection were tested against various epithelial, monocyte and endothelial cell lines (A549, HTB44, primary renal epithelial, U937 and Ea-hy 926). The test used for detecting binding antibodies was a simple, indirect immunofluorescence flow cytometric technique. The level of IgG antibodies directed against the test cell lines was examined in the sera of patients with mild or severe rejection and compared to those of patients showing no signs of rejection. Patients with chronic rejection were found to have increased levels of antibodies (IgG and IgM) when compared to patients with either end-stage renal failure or patients with stable post-transplant renal function. Antibodies detected by the present technique were directed against antigens found on all cell lines tested, and immunoblotting indicated that they were directed against non-HLA antigens. In conclusion, monitoring for the presence of such antibodies may provide a valuable prognostic indicator of graft rejection in renal transplant patients.

Antibodies↗
PubMed1995

Developing the ideal immunosuppressive protocol by internal audit.

To identify the best immunosuppressive protocol in a centre where five different regimens are employed, 227 consecutive renal recipients who were transplanted over a 2.5-year period were studied. The five different regimens employed were cyclosporin monotherapy, dual therapy (cyclosporin and prednisolone), triple therapy (cyclosporin, azathioprine, prednisolone), antithymocyte globulin (ATG) followed by dual therapy and ATG followed by triple therapy. Recipients were chosen for the different regimens according to HLA mismatch, positive donor crossmatch due to IgM, regraft and delayed graft function. The group with the lowest risk, cyclosporin monotherapy, had the highest acute rejection rate, with only 13% free of acute rejection (in comparison to triple immunosuppression, P = 0.024, chi-square test). The overall infection rate and graft success rate were similar between the different groups.

Adult↗
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↗