Prognostic indicators for endomyocardial biopsies: intragraft IL-2 and IFN-gamma are associated with poor longterm survival of cardiac allografts

Abstract

Currently the diagnosis of cardiac allograft rejection depends on morphologic analysis of paraffin sections of endomyocardial biopsies. The clinical decision of when lo treat rejection, especially if the patient is well, remains a difficult decision. We questioned if expression of cytokines and other activation molecules was predictive of a given rejection episode leading to fata! rejection vs. longterm survival. Hence, a rat model of cardiac allograft rejection was established whereby a clinically relevant protocol of peri-transplant injection of donor spleen cells, plus a single injection of cyclosporin 2 days post-transplant, induced longterm allograft survival (>90 d). whereas unirealed controls rejected by day 7. We undertook immunoperoxidase localization of various leucocyte populations, cytokines and markers of cytokine-induced immune activation. Whilst H&E staining of paraffin sections at day 7 post-Tx showed grade Illb rejection for both groups, the results of immunoperoxidase staining were markedly different: Group No Rx Spleen Cells plus CsA (day 7) (day 7) (day 93) IL-2R (CD25) 21 ± 3 1 ± 1 ** 0 MHC Class 11+ cells 57 ± 11 21 ± 14 * 30 ± 8 PCNA 26 ± 4 5 ± 1 ** not done IL-2 10 ± 5 0 ** 0 IFN-gamma 7 ± 5 1 ± 1 ** 0 * p ** p Moreover, uprcgulation of endothelial ICAM-1 expression and downregulation of thrombomodulin were seen in untreated but not treated groups. Thus, despite identical grading of cardiac rejection using standard criteria applied to H&E-slained paraffin sections, immunohistologic demonstration of key pro-inflammatory cytokines IL-2 and IFN-gamma, as well as the activalion molecules IL-2R and PCNA (proliferating cell nuclear antigen), allowed clearcut prediction of those cardiac allografts which would result in acute rejection versus those likely lo achieve longterm survival. This approach may (a) improve the accuracy of diagnosis of clinical cardiac allograft rejection. (b) predict Ihe outcome of a rejection episode, and (c) increase overall survival rales and decrease mortality from infection, by decreasing immunosuppressive requirements in allografts found lo show prognostic indicators of longterm survival.