The pathology of heart and lung transplantation

Immunosuppression, eotaxin and the diagnostic changes in eosinophils that precede early acute heart allograft rejection

Peripheral blood eosinophil counts (EOS) are undetectable in 40% blood samples sent for routine haematology at Papworth Hospital during the first 3 months after heart transplantation (HTx). Increases in EOS usually precede the development of allograft rejection by a median of 4 days. We compared the effects of cyclosporin (dose and total blood concentration), prednisolone (dose and both total and unbound plasma concentrations) and azathioprine, as well as plasma concentrations of the CCR-3 chemokines, eotaxin and RANTES, on changes in EOS in 47 consecutive HTx recipients, with a median follow-up of 90 (IQR 85-95) days. Multivariate analysis confirmed the independent association between both prednisolone dose (P<0.0001) and eotaxin (P<0.0001) and changes in EOS. The plasma eotaxin concentration was, in turn, most closely associated with the cyclosporin dose (P<0.001) and plasma prednisolone concentration (P=0.022). The blood cyclosporin concentration (P=0.028), EOS (P=0.012) and prednisolone dose (P=0.015) were all independently associated with the risk of treated acute rejection. When prednisolone pharmacokinetic parameters were substituted for the prednisolone dose in this multivariate model, only the pharmacokinetic parameter retained a significant association with the risk of rejection. Changes in EOS preceding cardiac allograft rejection are directly associated with plasma eotaxin concentrations and indirectly with prednisolone dosage. Cyclosporin may also indirectly influence these changes by inhibiting eotaxin production. EOS, prednisolone dose and blood cyclosporin concentrations were independently associated with the risk of acute rejection. The total and unbound fractions of prednisolone in plasma appear to be even more closely related to rejection but are difficult to measure. Monitoring EOS, as a surrogate measure of prednisolone immunosuppression, may be more cost-effective for controlling rejection than conventional cyclosporin monitoring in the first 6 weeks after HTx.

Transplant histopathology for the general histopathologist

The number of patients undergoing solid organ transplants and surviving long-term has increased enormously in the last 10 years. This means that pathologists in non-specialist transplant centres are increasingly involved in the interpretation of biopsy and autopsy material from allograft recipients. This includes evaluation of allograft histology, or specimens from other native tissues, which nonetheless still have to be assessed in the setting of transplantation and immunosuppressive therapy. In this first review article we will provide an overview of the pathology of lung transplantation, and briefly describe heart and pancreatic transplants, as well as aspects of general surgical pathology and the role of the autopsy in these patients.

Randomized trial of blood eosinophil count monitoring as a guide to corticosteroid dosage adjustment after heart transplantation

BACKGROUND

Increases in blood eosinophil counts (EOS) beyond 0.06 x 10(9)/liter precede treated heart allograft rejection. An oral prednisolone dose of 0.35 mg/kg/day usually suppresses EOS below this threshold.

METHODS

We designed a randomized trial to compare our empirical protocol for steroid dose adjustment with a novel protocol guided by EOS monitoring during the first 3 months after heart transplantation. Eighty patients were randomized to either have their EOS reported and used for steroid dose adjustment (RG; n=40), or not reported (NG; n=40). RG patients had their steroid dosage increased if EOS exceeded 0.06 x 10(9)/liter.

RESULTS

RG patients had an 83% lower risk of treated rejection (P=0.035) and lower median intravenous dose of methyl-prednisolone (P=0.017) than NG during the first 6 postoperative weeks. The proportion of diagnostic increases in EOS that were followed within 2 weeks by treated rejection was 42% greater in NG than RG (P=0.0001), compatible with a direct impact of EOS-guided prednisolone dose adjustment on the risk of subsequent rejection. Overall, RG had less than half the risk of rejection of any grade (P<0.001) and significantly more rejection-free biopsies than NG (P=0.001). The mean oral prednisolone dosage was significantly greater in RG than NG during the first (P=0.014) and second (P=0.001) 6 weeks of follow-up. This did not increase the incidence of serious steroid-related side effects.

CONCLUSIONS

EOS monitoring is a simple, cheap, and effective means of optimizing steroid immunosuppression. Restriction of the EOS-guided steroid dosing protocol to periods of prolonged hospitalisation during the first 3 postoperative months should limit the requirement for higher prednisolone dosage without affecting immunosuppressive efficacy.

Randomized, trough blood cyclosporine concentration-controlled trial to compare the pharmacodynamics of Sandimmune and Neoral in de novo lung transplant recipients

The greater and more consistent absorption of cyclosporine from the microemulsion formulation (Neoral; Novartis Pharmaceuticals Ltd., Frimley, UK) when compared with that from the original form (Sandimmune; Novartis Pharmaceuticals Ltd., Frimley, UK) results in greater systemic exposure. Lung transplant recipients could particularly benefit from this enhanced exposure, but not at the expense of excessive cyclosporine toxicity. We compared the pharmacodynamics of Neoral and Sandimmune over the first postoperative year in 50 lung transplant recipients. Twenty-eight patients were randomly selected to receive Neoral and 22 to receive Sandimmune. Nine patients with cystic fibrosis (CF) were randomly selected independently (5, Neoral; 4, Sandimmune). Patients were maintained on similar trough blood cyclosporine concentrations (C0) throughout the 12-month follow-up. A limited blood sampling strategy was adopted to compare the pharmacokinetics of the two formulations at the end of weeks 1 to 4, and of weeks 13, 26, 39, 52. The influence of any difference between the pharmacokinetics of Neoral and Sandimmune on either efficacy or toxicity of the drug was investigated during the follow-up period. Patients in the Neoral and the Sandimmune groups were matched demographically. There were no differences in dose-normalized blood cyclosporine concentrations measured predose (C0) or 6 hours postdose between the two groups. However, the measurement at 2 hours postdose (C2) and the total AUC0-6 were significantly greater in the Neoral group in both CF and non-CF patients at all visits (p < 0.001). Non-CF patients required 9% lower doses of Neoral to achieve comparable C0 measurements to those patients receiving Sandimmune. However, patients with CF required 2 to 3 times the dose of both Neoral and Sandimmune to achieve the same C0 as non-CF patients. The linear rejection rate in the Sandimmune group was 1.87 episodes per patient year, which was similar to the rejection rate of 1.97 episodes per patient year in the Neoral group. Serial lung function, blood biochemistry and hematology, mortality and the incidence of severe renal dysfunction, hypertension, infection, seizures, and new-onset diabetes were all similar in the two groups. Despite equivalent C0, those in the Neoral group were consistently exposed to greater blood cyclosporine concentrations during the dosing interval than those in the Sandimmune group. This did not increase the incidence of serious cyclosporine-associated side effects or influence the rate of acute rejection either. When data from the Neoral and Sandimmune groups were combined, measurements of C0 but not C2 or C6 were associated with the risk of acute lung allograft rejection.