Search

Purpose of Review: Progress of ventricular assist devices (VAD) technology led to improved survival and apparently low morbidity. However, from the European perspective, updated analysis of EUROMACS reveals a somewhat less impressive picture with respect to mortality and morbidity., Recent Findings: We describe the great demand of cardiac allografts versus the lack of donors, which is larger in Europe than in the United States. Technical progress of VADs made it possible to work out a modern algorithm of bridge-to-transplant, which is tailored to the need of the particular patient. We analyze the burden of patients undergoing bridge-to-transplant therapy. They are condemned to an intermediate step, coupled with additional major surgery and potential adverse events during heart transplantation., Summary: Based on current registry data, we do have to question the increasingly popular opinion, that the concept of heart transplantation is futureless, which seems to be for someone who treats and compares both patients (VAD and heart transplantation) in daily practice, questionable. Up to now, left ventricular assist device therapy remains a bridge to a better future, which means a bridge to technical innovations or to overcome the dramatic lack of donors in Europe.

Non-melanoma skin cancers (NMSCs) are the most common malignancies after solid organ transplantation. Their incidence increases with time after transplantation. Calcineurin-inhibitors (CNIs) and azathioprine are known as skin neoplasia-initiating and -enhancing immunosuppressants. In contrast, increasing clinical experience suggests a relevant antiproliferative effect of mammalian target of rapamycin inhibitors, also named proliferation signal inhibitors (PSIs). We report the case of a cardiac allograft recipient with an impressive and consolidated reduction of recurrent NMSC, observed after conversion from CNI-therapy to a PSI-based protocol., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Vascular endothelial (VE)-cadherin is an essential protein of adherens junctions of endothelial cells and plays a pivotal role in vascular homeostasis. Mammalian target of rapamycin complex 2 (mTORC2) deficient mice display defects in fetal vascular development. Blocking mTOR or the upstream kinase phosphoinositide 3-kinase (PI3K) led to a dose-dependently decrease of the VE-cadherin mRNA and protein expression. Immunofluorescent staining showed a strongly decreased expression of VE-cadherin at the interface of human umbilical endothelial cells (HUVECs) followed by intercellular gap formation. Herewith, we demonstrated that the expression of VE-cadherin is dependent on mTOR and PI3K signaling.

Background: Rapamycines, sirolimus (SRL) and everolimus (ERL), are proliferation signal inhibitors (PSIs). PSI therapy often leads to edema. We hypothesized that increased oxidative stress in response to PSIs may modulate the expression of vascular endothelial (VE)-cadherin on endothelial cells (ECs) and, subsequently, vascular permeability, which in turn may be involved in the development of edema., Methods: Experiments were performed on human umbilical vein ECs (HUVECs). Oxidative stress was measured by dichlorofluorescein-diacetate. Expression of VE-cadherin was evaluated by immunofluorescent staining and western blot analysis. Endothelial "permeability" was assessed using a transwell model., Results: SRL and ERL, at concentrations of 1, 10 and 100 nmol/liter, enhanced oxidative stress (SRL: 24 +/- 12%, 29 +/- 9%, 41 +/- 13% [p < 0.05, in all three cases]; ERL: 13 +/- 10%, 27 +/- 2%, 40 +/- 12% [p < 0.05, in the latter two cases], respectively) on HUVECs, which was inhibited by the anti-oxidant, N-acetyl-cysteine (NAC) and, to a lesser extent, by the specific inhibitor of nitric oxide synthase, N-Omega-nitro-L-arginine methylester. By the use of NAC, VE-cadherin expression remained comparable with control, according to both immunocytochemistry and western blot analysis. Permeability was significantly increased by SRL and ERL at 100 nmol/liter (29.5 +/- 6.4% and 33.8 +/- 4.2%, respectively); however, co-treatment with NAC abrogated the increased permeability., Conclusions: EC homeostasis, as indicated by VE-cadherin expression, may be damaged by SRL and ERL, but resolved by the anti-oxidant NAC.

We recently reported a complete change in the endothelial ABO histo-blood group phenotype of a cardiac allograft long term after B to O mismatched transplantation. In the context of the current controversy on graft recolonization with recipient endothelial cells and its importance in the development of immunological unresponsiveness, we monitored the expression of endothelial ABH histo-blood group antigens of 10 ABO-compatible, non-identical cardiac allografts over an observation period of at least 30 months. ABH antigens as well as markers for endothelial cells, erythrocytes and thrombocytes were investigated retrospectively by immunohistochemistry using monoclonal antibodies on sections of formalin-fixed, paraffin-embedded biopsies and were evaluated semi-quantitatively by microscopy. In contrast to our earlier finding of the change in the endothelial ABO histo-blood group phenotype long term after ABO- mismatched transplantation, we could not confirm this change in 10 compatible but non-identical cases.

The ability of experienced anaesthetists to discern oxygen saturation by listening to the tones of a Datex AS3 pulse oximeter was examined. Five-second samples were recorded using a high fidelity patient simulator and replayed singly and in pairs. Whilst the lower saturations were generally recognized as lower, the perceived range was greatly compressed. Median perceived estimates for 70% saturation was 89%, for 80% was 93% and for 94% was 94%. When comparing pairs of samples, the direction of the difference was correctly discerned by 70% of anaesthetists for differences of 2%, rising to 95% for differences of greater than 8% oxygen saturation. The magnitude of the difference was consistently underestimated. With an actual difference of 20%, the median estimate was 5%. The results indicate that while qualitative estimate changes in oxygen saturation are moderately reliable, quantitative estimation is severely limited by a compromised perceived scale. This may lead to underestimation of the severity if the auditory signal is relied on in isolation. A non-linear (musical) scale may prove more appropriate and should be investigated. Testing experienced anaesthetists demonstrated that most could detect the direction, but not the magnitude of a change in saturation by listening to the change in pitch of a Datex AS3 pulse oximeter tone.

For the first time in the literature to date, we report 2 cases of transplantation of yeast-infected cardiac allografts. In both cases, endocardial vegetations were observed before graft implantation. Microbiologic samples grew yeasts: Rhodotorula glutinis was found close to the left atrial appendage in the first case and Candida parapsilosis was identified in a vegetation located at the base of the tricuspid valve in the second case. We discuss the possible routes of donor organ infection and management of these 2 unusual cases.

Background: Activation of endothelial cells (EC) in xenotransplantation is mostly induced through binding of antibodies (Ab) and activation of the complement system. Activated EC lose their heparan sulfate proteoglycan (HSPG) layer and exhibit a procoagulant and pro-inflammatory cell surface. We have recently shown that the semi-synthetic proteoglycan analog dextran sulfate (DXS, MW 5000) blocks activation of the complement cascade and acts as an EC-protectant both in vitro and in vivo. However, DXS is a strong anticoagulant and systemic use of this substance in a clinical setting might therefore be compromised. It was the aim of this study to investigate a novel, fully synthetic EC-protectant with reduced inhibition of the coagulation system., Method: By screening with standard complement (CH50) and coagulation assays (activated partial thromboplastin time, aPTT), a conjugate of tyrosine sulfate to a polymer-backbone (sTyr-PAA) was identified as a candidate EC-protectant. The pathway-specificity of complement inhibition by sTyr-PAA was tested in hemolytic assays. To further characterize the substance, the effects of sTyr-PAA and DXS on complement deposition on pig cells were compared by flow cytometry and cytotoxicity assays. Using fluorescein-labeled sTyr-PAA (sTyr-PAA-Fluo), the binding of sTyr-PAA to cell surfaces was also investigated., Results: Of all tested compounds, sTyr-PAA was the most effective substance in inhibiting all three pathways of complement activation. Its capacity to inhibit the coagulation cascade was significantly reduced as compared with DXS. sTyr-PAA also dose-dependently inhibited deposition of human complement on pig cells and this inhibition correlated with the binding of sTyr-PAA to the cells. Moreover, we were able to demonstrate that sTyr-PAA binds preferentially and dose-dependently to damaged EC., Conclusions: We could show that sTyr-PAA acts as an EC-protectant by binding to the cells and protecting them from complement-mediated damage. It has less effect on the coagulation system than DXS and may therefore have potential for in vivo application., (Copyright Blackwell Munksgaard, 2004)

Acute or even hyperacute humoral graft rejection, mediated by classical pathway complement activation, occurs in allo- and xenotransplantation due to preformed anti-graft antibodies. Intravenous immunoglobulin (IVIg) preparations can prevent complement-mediated tissue injury and delay hyperacute xenograft rejection. It is known that IgM-enriched IVIg (IVIgM) has a higher capacity to block complement than IVIgG. Different IVIgs were therefore tested for specificity of complement inhibition and effect on anti-bacterial activity of human serum. IVIgM-I (Pentaglobin), 12% IgM), IVIgM-II (IgM-fraction of IVIgM-I, 60% IgM), and three different IVIgG (all >95% IgG) were used. The known complement inhibitor dextran sulfate was used as control. Hemolytic assays were performed to analyze pathway-specificity of complement inhibition. Effects of IVIg on complement deposition on pig cells and Escherichia coli were assessed by flow cytometry and cytotoxicity as well as bactericidal assays. Complement inhibition by IVIgM was specific for the classical pathway, with IC50 values of 0.8 mg/ml for IVIgM-II and 1.7 mg/ml for IVIgM-I in the CH50 assay. Only minimal inhibition of the lectin pathway was seen with IVIgM-II (IC50 15.5 mg/ml); no alternative pathway inhibition was observed. IVIgG did not inhibit complement in any hemolytic assay. Classical pathway complement inhibition by IVIgM was confirmed in an in vitro xenotransplantation model with PK15 cells. In contrast, IVIgM did not inhibit (mainly alternative pathway mediated) killing of E. coli by human serum. In conclusion, IgM-enriched IVIg is a specific inhibitor of the classical complement pathway, leaving the alternative pathway intact, which is an important natural anti-bacterial defense, especially for immunosuppressed patients.

We showed recently that low molecular weight dextran sulfate (DXS) acts as an endothelial cell (EC) protectant and prevents human complement- and NK cell-mediated cytotoxicity towards porcine cells in vitro. We therefore hypothesized that DXS, combined with cyclosporine A (CyA), could prevent acute vascular rejection (AVR) in the hamster-to-rat cardiac xenotransplantation model. Untreated, CyA-only, and DXS-only treated rats rejected their grafts within 4-5 days. Of the hearts grafted into rats receiving DXS in combination with CyA, 28% survived more than 30 days. Deposition of anti-hamster antibodies and complement was detected in long-term surviving grafts. Combined with the expression of hemoxygenase 1 (HO-1) on graft EC, these results indicate that accommodation had occurred. Complement activity was normal in rat sera after DXS injection, and while systemic inhibition of the coagulation cascade was observed 1 h after DXS injection, it was absent after 24 h. Moreover, using a fluorescein-labeled DXS (DXS-Fluo) injected 1 day after surgery, we observed a specific binding of DXS-Fluo to the xenograft endothelium. In conclusion, we show here that DXS + CyA induces long-term xenograft survival and we provide evidence that DXS might act as a local EC protectant also in vivo.

Background: The innate immune system, including complement and natural killer (NK) cells, plays a critical role in activation and damage of endothelial cells (ECs) during xenograft rejection. The semisynthetic proteoglycan analog dextran sulfate (DXS, molecular weight 5,000) is known to inhibit the complement and coagulation cascades. We hypothesized that DXS may act as an "EC-protectant" preventing complement and NK lysis by functionally replacing heparan sulfate proteoglycans that are shed from the EC surface on activation of the endothelium., Methods: Binding of DXS to ECs, deposition of human complement, cytotoxicity, and heparan sulfate expression after exposure to normal human serum were analyzed by flow cytometry. The efficacy of DXS to protect ECs from xenogeneic NK cell-mediated cytotoxicity was tested in standard 51Cr-release assays., Results: DXS dose-dependently inhibited all three pathways of complement activation. Binding of DXS to porcine cells increased on treatment with human serum or heparinase I and correlated positively with the inhibition of human complement deposition. This cytoprotective effect of DXS was still present when the challenge with normal human serum was performed up to 48 hr after DXS treatment of the cells. DXS incubation of porcine ECs with and without prior tumor necrosis factor-alpha stimulation reduced xenogeneic cytotoxicity mediated by human NK cells by 47.3% and 25.3%, respectively., Conclusions: DXS binds to porcine cells and protects them from complement- and NK cell-mediated injury in vitro. It might therefore be used as a novel therapeutic strategy to prevent xenograft rejection and has potential for clinical application as an "EC protectant."

Dextran sulfate of 5000 molecular weight (DXS 5000) is known to block complement activation as well as the intrinsic coagulation cascade by potentiation of C inhibitor. The effect of DXS 5000 on hyperacute rejection (HAR) was tested in pig-to-human xenotransplantation models. For in vitro testing, a cytotoxicity assay was used with the pig kidney cell line PK15 as target cells and fresh, undiluted human serum as antibody and complement source. Ex vivo pig lung perfusion was chosen to assess DXS 5000 in a physiologic model. Pig lungs were perfused with fresh, citrate-anticoagulated whole human blood to which 1 or 2 mg/ml DXS 5000 were added; the lungs were ventilated and the blood de-oxygenated. Pulmonary vascular resistance (PVR) and blood oxygenation (deltapO2) were monitored throughout the experiment. Autologous pig blood and human blood without DXS 5000 served as controls. In the PK 15 assay DXS 5000 led to a complete, dose-dependent inhibition of human serum cytotoxicity with an average IC50 of 43 +/- 18 microg/ml (n=8). Pig lungs perfused with untreated human blood (n=2) underwent HAR within 105 +/- 64 min, characterized by increased PVR, decrease of deltapO2, and generalized edema. Microscopically, capillary bleeding as well as deposition of human antibodies, complement and fibrin could be observed. Addition of DXS 5000 (n=4) prolonged lung survival to 170 +/- 14 min for 1 mg/ml and 250 +/- 42 min for 2 mg/ml. and PVR values as well as edema formation were comparable to control lungs that were perfused with autologous pig blood (n=2). Activation of complement (activation products in serum, deposition on lung tissue) and the coagulation system (fibrin monomers) were significantly diminished as compared to human blood without DXS 5000. Binding of anti-Gal antibodies was not influenced, and in vitro experiments showed no evidence of complement depletion by DXS 5000. In conclusion, DXS 5000 is an efficient complement inhibitor in pig-to-human xenotransplantation models and therefore a candidate for complement-inhibitory/anti-inflammatory therapy either alone or in combination with other substances and warrants further investigation.

Pig-to-human xenotransplantation might be an option to overcome the increasing shortage of human donor organs. However, naturally occurring antibodies in human blood against the Galalpha1-->3Gal antigen on pig endothelial cells lead to hyperacute or, if prevented, acute or delayed vascular rejection of the pig graft. The purpose of this study was therefore to evaluate synthetic oligosaccharides with terminal Galalpha1-->3Gal to inhibit antigen-binding and cytotoxicity of anti-alphaGal antibodies against pig cells. Different oligosaccharides were synthesized chemically and by a combined chemico-enzymatic approach. These included monomeric di-, tri-, and pentasaccharides, a polyacrylamide-conjugate (PAA-Bdi), as well as di-, tetra-, and octamers of Galalpha1-->3Gal. All were tested for inhibitory activity by anti-alphaGal ELISA and complement-dependent cytotoxicity tests. PAA-Bdi was the best inhibitor of binding as well as cytotoxicity of anti-alphaGal antibodies. Monomeric oligosaccharides efficiently prevented binding of anti-alphaGal IgG, but less well that of anti-alphaGal IgM, with tri- and pentasaccharides showing a better efficacy than the disaccharide. The two trisaccharides Galalpha1-->3Galbeta1-->4GlcNAc and Galalpha1-->3Galbeta1-->3GlcNAc were equally effective. Oligomers of Galalpha1-->3Gal were more effective than monomers in blocking the binding of anti-alphaGal IgG. However, they could not block IgM binding, nor could they match the efficacy of PAA-Bdi. We conclude that oligosaccharides with terminal Galalpha1-->3Gal, most effectively as PAA-conjugates, can prevent binding and cytotoxicity of human anti-alphaGal in vitro. The PAA-Bdi conjugate might be most suited for use as a Sepharose-bound immunoabsorption material.

Prophylaxis and treatment with i.v. immunoglobulins must envisage preparations from normal or hyperimmunised human donors, animals (horses and rabbits) as well as monoclonal and genetically and proteomically engineered chimeric or recombinant antibodies. The latter group of antibody sources from the bioreactor source must be seen in the context of traditional antibody therapy, including passive immunization, general antibody substitution and provision of lost immune regulatory capacities such as downregulation of complement activation, attenuation of Fc receptor apparatus as well as anti-idiotypic potential. Beyond summarizing the present evidence based indications the present review is an outlook at the doorstep for future possibilities to improve precision of antibody dependent treatments and avoiding side effects which formerly compromised widespread use.

The natural occurrence of complement-activating anti-Galalpha1-3Gal antibodies (anti-Gal) in human serum is considered as a major obstacle to xenotransplantation. In this study we determined anti-Gal in sera of 200 healthy volunteers (100 male, 100 female) of different age groups using an IgG- and IgM-isotype specific ELISA. In addition, we used a direct hemagglutination test involving rabbit erythrocytes (E(R)), which are known for abundant surface expression of the Galalpha1-3Gal antigen. The measured arbitrary ELISA units (U) for anti-Gal ranged from 5 to 204 U (77+/-47; mean +/- 1 SD) for IgM, and from 1 to 162 U(73+/-32) for IgG. Anti-E(R) hemagglutination titers were between 1: 65536 and 1: 64 (mean 1: 703), with 75% of all serum samples being in the range of 1: 8192-1: 512. Specificity of the tests was determined by immunoabsorption of anti-Gal on Sepharose-coupled synthetic Galalpha1-3Gal antigen, which reduced ELISA as well as agglutination titers by 90% or more. Overall, inter-individual differences of both anti-Gal ELISA values and E(R) agglutination titers exceeded age-, gender-, or ABO-type related changes. A tendency was found to higher anti-Gal IgM values in women than in men (P < 0.005 by Student's t-test), whereas the gender-difference for anti-Gal IgG or E(R) titers was not significant. Application of the anti-Gal ELISA as well as the E(R) agglutination assay for pre-transplant screening of potential pig xenograft recipients is discussed.

Background and Aims of the Study: The study aim was to determine the risk of thromboembolic and bleeding complications in patients with mechanical heart valve prostheses who underwent non-cardiac surgery under different regimens of perioperative anticoagulation. Data were analyzed on the basis of surgery type and underlying disease., Methods: A series of 235 patients (mean age 63 +/- 4.5 years) with one or two mechanical heart valves underwent subsequent non-cardiac surgery comprising abdominal, vascular and thoracic, orthopedic, urologic, neurosurgery, ENT, plastic and reconstructive, and gynecologic operations. Mean interval between heart valve replacement and non-cardiac surgery was 3.9 +/- 3.3 years. Perioperative oral anticoagulation was managed by discontinuation of oral anticoagulation and intravenous heparin administration; or by discontinuation and early postoperative re-institution of oral anticoagulation without intravenous heparin; or by no withdrawal of oral anticoagulation. Patients with bioprostheses were excluded., Results: Overall hospital mortality during non-cardiac surgery was 2.9%. Thromboembolic events included cerebral embolism with transient deficit (n = 3), residual defect (n = 1) and irreversible defect (n = 1), as well as peripheral embolism (n = 11). Hemorrhagic complications included wound hematoma (n = 10) and increased postoperative bleeding (n = 8) with re-exploration in five patients. Thromboembolic complications occurred most often in patients with prosthetic mitral valve and atrial fibrillation; the lowest risk was in patients with sinus rhythm after aortic valve replacement. Most complications occurred after discharge and in patients with surgery for malignancy, within 10 days of instituting oral anticoagulation, and despite a therapeutic INR value., Conclusions: Minor surgical procedures can be performed safely without discontinuing anticoagulation. When major non-cardiac surgery is planned, discontinuing oral anticoagulation and starting perioperative intravenous heparin minimizes bleeding and thromboembolic risks. Thromboembolic complications may occur within one month of surgery, despite adequate oral anticoagulation, though permanent morbidity is low.

The use of xenografts could relieve the chronically inadequate supply of human organs for transplantation, but doubts have been expressed about the general acceptability of transplanting animal organs into human. Some researchers and clinicians have chosen to ignore negative attitudes towards clinical xenotransplantation, assuming that people will automatically embrace this new technology when it becomes available. A review of eight studies of attitudes to xenotransplantation did not reveal overwhelming support for it. Particularly negative views were expressed by acute care nurses. Primates have been the donors of choice in clinical xenotransplantation to date, but their continued use is a highly contentious option; the preferred animal donor is now clearly the pig. Animal farming for xenotransplantation is generally regarded as acceptable since animals provide food for man and are an accepted source of items for human use such as heart valves and insulin. Open debate about xenotransplantation must now take place, and present attitudes may change as a result of this. However, it remains to be seen whether xenografts will be widely accepted and used, and the extent to which the chronic shortage of organs for transplantation will thereby be alleviated.

Background: Vascular smooth muscle cell hyperplasia with resulting luminal narrowing is the main histologic feature of accelerated arteriosclerosis seen after organ transplantation (transplant arteriosclerosis) and after balloon angioplasty (restenosis). It limits long-term allograft survival, as well as the success rate of angioplasty. At present, effective prophylactic and therapeutic strategies for these complications are still missing. Studies of in vivo models of accelerated arteriosclerosis induced by allogeneic or mechanical injury to the vasculature indicate that certain immunosuppressive drugs have inhibitory properties on smooth muscle cell hyperplasia., Methods: This study summarizes the inhibitory effects of different immunosuppressive drugs in vitro on the growth factor-induced proliferation of vascular smooth muscle cells and endothelial cells isolated from human and rat thoracic aortas., Results: The immunosuppressants rapamycin and mycophenolic acid were potent in inhibiting smooth muscle and endothelial cell proliferation. Cyclosporine demonstrated some inhibition of smooth muscle and endothelial cell proliferation, but the inhibitory concentration50 (IC50) values were just below toxicity levels. FK506 revealed a moderate inhibitory activity but, interestingly, only for human cells. High concentrations of leflunomide inhibited in our experiments only rat smooth muscle and endothelial cell proliferation. Methylprednisolone showed a gradual inhibition over a broad concentration interval of rat and human smooth muscle cells and of rat but not of human endothelial cells., Conclusions: These data indicate that all of the established and new immunosuppressants tested have antiproliferative properties on vascular cells. Rapamycin was by far the most potent one. Therefore immunosuppressants, especiallyrapamycin and mycophenolic acid, may be used for prevention of accelerated arteriosclerosis.

Most Australian transplantation programs are severely restricted in their activities by a limited availability of cadaveric donor organs. To investigate possible reasons for this problem, an audit was undertaken over three 12-month periods of all deaths in 13 hospitals in New South Wales and the Australian Capital Territory. From 7406 deaths, 271 patients were classified as having been realistic, medically suitable potential donors. Of these, only 60 (22%) became actual donors. In the other 211 patients, donation did not occur because of unsuccessful resuscitation (30%), permission refusal by relatives (34%), and failure to identify or support the potential donors (36%). If the impediments to organ donation which were identified in this study could be overcome, allowing a greater number of potential donors to become actual donors, the chronic shortage of cadaveric donor organs for transplantation could be at least partly relieved.

There are many reasons why potential cadaveric organ donors may fail to become actual donors. These include permission refusal by the next of kin, incorrect assumptions about medical suitability and, occasionally, an excessive workload in the intensive care unit. Some potential donors currently regarded in Australia as "unrealistic" might become actual donors if attitudes were to change towards ventilation of patients with a clearly hopeless prognosis who have expressed a wish to be organ donors. "Required request" legislation ignores the wishes of the potential donor and "presumed consent" laws also present some ethical difficulties, but a suggested "required response" process could ensure that an individual's wishes concerning organ donation would be known and able to be carried out after death. For the present, however, it is clear that operating within existing Australian legislation and abiding by currently accepted codes of practice, we can still find considerable scope for improving cadaveric organ donation rates.

Most transplant programs in this country are significantly restricted by a chronic shortage of donor organs. This article examines the sources of transplantable organs, the concept of brain death, reasons why potential donors may be missed in hospitals, the often perceived difficulty in approaching next-of-kin, and the medical requirements and logistics of organ retrieval. The lives of many people are affected by organ donation and transplantation. For those receiving a transplant it can be a gift of incalculable value; for those who agree to donation it may represent one positive outcome from an otherwise tragic situation. These unique circumstances provoke a wide range of emotions and reactions. Health care professionals need to act responsibly towards both donor families and potential transplant recipients. Their involvement in the process of organ donation is an important part of their role in the care of critically ill or injured patients.

Rapamycin (RPM) is a macrolide fermentation product that prolongs rodent allograft survival more potently and effectively than cyclosporin A (CsA) and FK506. Experiments in vitro have shown that RPM inhibits lymphoproliferation by mechanisms of action that are different from other immunosuppressants. Much less is known, however, about the effects of RPM on immune cells in vivo compared to other immunosuppressive drugs. Others have shown that in vivo treatment with CsA suppresses the responsiveness of cells in the mixed lymphocyte response (MLR). Therefore, to investigate the effects of RPM in vivo, rats were treated with RPM and their lymphoid cells used as responder cells in the MLR. We confirmed that the proliferation of cells in the MLR was decreased after treatment with CsA in vivo. In contrast, treatment with RPM in vivo greatly increased the proliferative response to alloantigen in the MLR. These findings show that the effects of RPM and CsA on immune cells in vivo differ. Perhaps the cells proliferating in the MLR after in vivo RPM treatment play a role in the regulation of the immune system that enables this immunosuppressant to prolong allograft survival so effectively in rodents.

Objectives: To measure the potential for cadaver organ retrieval in New South Wales and to determine the reasons for potential donors failing to become actual donors., Design: Prospective audit of all patients dying in five hospitals in New South Wales between 1 December 1989 and 30 November 1990; quality assurance of the data by independent medical specialist and if disagreement by study committee., Patients: 2879 patients (100% of all deaths) yielding 364 patients with coma and 181 potential donors., Outcome Measures: Realistic medically suitable potential donor rate, missed potential donor rate, rate of potential donors with permission refused, donor rate, reasons for realistic medically suitable potential donors failing to become actual donors., Results: 2879 deaths yielded 73 medically suitable potential donors, resulting in 19 actual donors, 30 missed potential donors, 19 potential donors with permission refused, and five in whom adequate resuscitation failed. The most common reason for a potential donor failing to become an actual donor was a decision by the senior medical practitioner to withdraw or not to institute ventilatory or haemodynamic support (26/73). The second major obstacle was refusal of permission by the next of kin (17/73). Assuming that the potential donor rate was that implied by the observed donor rate (13/million population/year) the projected missed potential donor rate was 9/million population/year (95% confidence interval 4 to 15) and the projected rate of potential donors with permission refused was 13/million population/year (95% confidence interval 5 to 22). Assuming that the rate of potential donors in the study hospitals was the same as in the other New South Wales hospitals, the projected donor rate for New South Wales was 18/million population/year (10 to 26); the projected missed potential donor rate was 15/million population/year (7 to 23); and the projected rate of potential donors with permission refused was 18/million population/year (10 to 27)., Conclusions: The donor rate could be increased 70%-80% by overcoming the reluctance of medical practitioners to resuscitate missed potential donors and increased further by gaining permission for organ retrieval from the next of kin.