Promotion of incompatible allograft acceptance in rhesus monkeys given posttransplant antithymocyte globulin and donor bone marrow. II. Effects of adjuvant immunosuppressive drugs

Previous studies from this laboratory demonstrated prolonged acceptance of MHC-mismatched kidney allografts in rhesus monkeys treated with posttransplant rabbit antithymocyte globulin (RATG)* and donor-specific bone marrow (DBM). Here we have investigated the effect of adjunctive immunosuppressive drugs on induction of allogeneic unresponsiveness in this primate model. Parameters examined included median kidney allograft survival time (MST), development of specific antidonor T lymphocyte-mediated cytotoxicity (LMC) and antidonor antibody-dependent cellular cytotoxicity (ADCC). Posttransplant infusion of DBM in RATG-treated kidney allograft recipients resulted in 70 days MST and a dramatic reduction in the incidence of antidonor LMC. However, development of antidonor ADCC was similar to that of RATG controls, suggesting an immune deviation or split tolerance in these animals. Adjunctive azathioprine did not have a beneficial effect in recipients given RATG & DBM, resulting in decreased MST and increased antidonor LMC responses. In contrast, adjunctive cyclosporine (CsA) and low-dose prednisone (P) exerted an additive immunosuppressive effect resulting in a 50% increase in MST and no detectable antidonor LMC. However, CsA & P appeared to enhance the humoral alloimmune response, increasing the incidence of recipients with antidonor ADCC. Long-term graft survival in this group was limited by chronic rejection and especially by CsA-associated toxicity. These studies point out deterrents and also directions for optimizing adjunctive immunosuppression in primates treated with posttransplant RATG & DBM. The results with CsA are relatively encouraging. However, the prevalence of alloantibody and of chronic rejection in these animals suggests that more homogeneous success with tolerance induction in this model may require adjunctive immunosuppressive strategies that reduce humoral immunity.

Protein adsorption on polymer surfaces: calculation of adsorption energies

In an attempt to understand the mechanisms of protein adsorption at the solid-liquid interface, we have calculated the interaction potential energy between the protein and the polymer surface by a computer simulation approach. The adsorption of four proteins--lysozyme, trypsin, immunoglobulin Fab, and hemoglobin--on five polymer surfaces was examined. The model polymers used for the calculation were polystyrene, polyethylene, polypropylene, poly(hydroxyethyl methacrylate), and poly(vinyl alcohol). All possible orientations of the protein on the polymer surfaces were simulated and the corresponding interaction energies for the initial contact stage of protein adsorption were calculated. In the calculation of interaction energies, the hydrophobic interaction was not treated explicitly owing to the difficulty in the theoretical treatment. The results showed that the interaction energy was dependent on the orientation of the protein on the polymer surfaces. The energy varied from -850 to +600 kJ/mol with an average of about -155 kJ/mol. The interaction energy was also dependent on the type of polymer. The average interaction energies of the four proteins with poly(vinyl alcohol) were always lower than those with the other polymers. The interaction energy was not dependent on the protein size. It was found that the dispersion attraction played the major role in protein adsorption on neutral polymer surfaces.

A pancreatic tumour presenting as a ruptured spleen

We report a case of spontaneous rupture of the spleen due to invasion from a pancreatic tumour. We are unaware of any similar case having been reported in the literature.

Enzyme-digestible swelling hydrogels as platforms for long-term oral drug delivery: synthesis and characterization

A method was developed for synthesizing enzyme-digestible swelling hydrogels. Albumin molecules were modified using glycidyl acrylate to introduce vinyl groups. The functionalized albumin molecules participated as cross-linkers in the polymerization of vinyl monomers, such as acrylic acid or acrylamide. The extent of chemical modification of albumin was an important variable in controlling the cross-linking ability. The albumin in the synthesized hydrogels retained its property of enzymatic digestion by proteolytic enzymes. The kinetics of swelling and enzymatic digestion of the hydrogels were examined using various enzyme concentrations. It was observed that the digestion kinetics were largely determined by the relative concentrations of albumin and enzyme. The potential application of the enzyme-digestible swelling hydrogels as platforms for long-term oral drug delivery is discussed.

An unusual case of oesophageal rupture treated by transhiatal oesophagectomy

Spontaneous rupture of the oesophagus is an uncommon surgical emergency. A case is presented in which the extensive nature of the rupture precluded standard methods of treatment and was treated by transhiatal oesophagectomy.

The histone octamer, a conformationally flexible structure

The conformation of the histone octamer complex in solution has been shown, by circular dichroism studies, to be highly dependent on the nature of the salt milieu and its concentration. In 2 M NaCl, the complex has 43.5% alpha-helix, 16% beta-sheet, and 40.5% random structure. In 2.3 M (NH4)2SO4, the octamer has 49.0% alpha-helix and 51% random structure. These results partially explain the discrepant results obtained by the X-ray analysis of crystals obtained under varying conditions.

Promotion of incompatible allograft acceptance in rhesus monkeys given posttransplant antithymocyte globulin and donor bone marrow. I. In vivo parameters and immunohistologic evidence suggesting microchimerism

This report extends previous studies demonstrating that prolonged acceptance of incompatible kidney allografts in rhesus monkeys can be achieved by a short recipient rabbit antithymocyte globulin (RATG) treatment course followed by donor bone marrow infusion on day 12 without a requirement for chronic immunosuppression. Serial studies of antilymphocyte cyctotoxic antibody in recipients' sera following RATG injections showed pan-lymphocyte-reactive antibody present until day 10 posttransplant. On days 11 and 12, pan-lymphocyte-reactive antibody was no longer detectable, but cytotoxic antibody specific for mature T cells remained in recipients' sera. These findings might explain the critical time relationship between antithymocyte globulin treatment and donor bone marrow infusion, and further suggest that the tolerance-promoting cell in donor bone marrow is not a mature T cell, but rather a pre-T or a non-T cell. Finally, it was found that this treatment protocol resulted in development of lymphoid nodules in the transplanted kidney that express a CD8-positive, FcIgG-receptor-positive phenotype and appear to be of donor origin. The possibility of a veto cell type of mechanism is discussed as an explanation for the promotion of allograft acceptance in this model.

Surface characterization of biomaterials by immunogold staining--quantitative analysis

The labeling of target proteins by immunogold particles has been analyzed based on Einstein's law of Brownian motion. The theory was confirmed from the experiments which employed antifibrinogen gold markers to label fibrinogen molecules adsorbed on the polyethylene surface. The theory predicts that the degree of labeling depends on the concentration of gold markers, temperature, medium viscosity, size of gold markers, and staining time. Of these factors most important is the concentration of immunogold particles. Small change in the marker concentration results in a significant variation in the staining efficiency when other variables are kept constant. The effect of temperature is always accompanied with that of the medium viscosity. There is a linear relationship between the degree of labeling and the temperature when the viscosity effect is combined. The staining of fibrinogen molecules adsorbed on the polyethylene surface at three different temperatures shows a temperature dependence which is in close agreement with the theory. The degree of labeling is inversely related to a square root of the size of gold markers. This analysis makes it possible to maximize the staining sensitivity and to improve the reproducibility of the labeling. Thus, the immunogold staining under a well defined condition allows quantification as well as positive identification and localization of target proteins. This technique has been used to study protein adsorption on biomaterials.

The effect of fibrinogen sialic acid residues on ex vivo platelet deposition on biomaterials

The effect of fibrinogen sialic acid residues on platelet deposition onto polymer surfaces was examined using a canine ex vivo shunt model. To test the hypothesis that desialylated fibrinogen may enhance platelet deposition when precoated on biomaterials, canine fibrinogen was desialylated and precoated on polyvinyl chloride (PVC) shunts. When protein-coated PVC shunts were exposed to flowing whole blood, both the native and the desialylated fibrinogen elicited the same profile of platelet deposition. This study indicates that platelet deposition and thrombus formation on biomaterial surfaces is not mediated by a mechanism which involves the sialic acid residues of fibrinogen.

Human leukocyte antigen (HLA) in Korean patients with autoimmune thyroid diseases

In previous studies, there has been evidence of different allelic associations with a particular disease among various ethnic groups. The present study was done to investigate the associations between HLA and autoimmune thyroid diseases in the Korean. We found no association between Graves’ disease and HLA-B8 or -B35. However, increased frequencies of HLA-A11 and -DRw8, and the decreased frequencies of HLA-A10 and B12 were found in patients with Graves’ disease. In the cases of Hashimoto’s disease, the frequencies of HLA-A2 and -DRw8 were found to be significantly increased and the frequency of HLA-DRw6y decreased. These data indicate that the association between autoimmune thyroid disease and HLA in the Korean would appear to be different from that in most other racial groups, including Caucasians, Japanese and Chinese.

Acute surface-induced thrombosis in the canine ex vivo model: importance of protein composition of the initial monolayer and platelet activation

The initial events occurring at the blood-polymer interface were examined using a canine ex vivo arteriovenous shunt model. Thrombogenic (fibrinogen) and nonthrombogenic (albumin) proteins were preadsorbed on poly(vinyl chloride), polyethylene, and silicone rubber shunt surfaces, and the blood responses were analyzed using the platelet deposition profile as an indicator of surface thrombogenicity. The distributions of preadsorbed protein molecules on the various polymer surfaces were studied using an immunogold bead (colloidal gold particles coated with antibodies) staining technique and shown to be homogeneous. A sequential protein adsorption technique was developed to probe the nature of competitive protein adsorption and to observe the effect of surface protein concentration on thrombogenicity. The thrombogenicity of a surface was determined by the composition of the initial protein layer rather than the total concentration of protein on the polymer surfaces. The composition of this layer determines the extent of platelet activation and the adhesive strength between platelets and the polymer surface.