Contribution of the expression of ICAM-1, HLA-DR and IL-2R to the diagnosis of acute rejection in renal allograft aspirative cytology

Abstract

Abstract Acute rejection is associated with a poor long-term prognosis for renal allografts. Sequential fine-needle aspiration cytology (FNAC) has been used to monitor rejection. However, FNAC diagnoses rejection only when the infiltrating cells are already damaging the graft and, in some borderline cases with a low increment of inflammatory cells in the graft, FNAC lacks the specificity to diagnose rejection. In these cases, the number of inflammatory cells within the graft can decline, stabilize or increase with time. In this study, we sought to determine whether the analysis of the expression of ICAM-I, HLA-DR and IL-2R along with borderline FNAC results increases the specificity to diagnose rejection. Of 117 FNAC samples taken from 24 patients after renal transplantation, 85 (72 %) were considered suitable for cytological analysis. Of these patients, 9 (37 %) did not suffer an acute cellular rejection (ACR) episode and 15 (63 %) had at least one ACR episode. ICAM-1 and IL-2R were studied using an immune-peroxidase technique. The ICAM-1 results are expressed as the percentage of tubular cells in the aspirate stained with this marker and the IL-2R results are expressed as the absolute number of positively stained lymphocytes in the whole cytopreparation. With a total corrected increment (TCI) of > 3 there was a sharp increase in the specificity index for rejection that reached almost 100 % at a TCI of ≤ 4. Sensitivity for rejection at this level was only 20 %. Between a TCI of 2.5 and 2.9 the sensitivity increased to 75 %, with specificity for rejection around 75 %. There was an upregulation of ICAM-1 and IL-2R when FNAC diagnosed rejection but with a large overlap of the results when compared either to normal graft or acute tubular neurosis. The mean TCI during the week preceding the rejection episode was 2.5 and the TCI reached a mean value of ≤ 3 only during rejection. The peak ICAM-1 and IL-2R expression occurred during the week preceding the clinically evident rejection episode. The expression of ICAM-1 by ≥ 70 % of the tubular cells increased the specificity for rejection of a TCI of ≥ 2.5 to 100 %. In the same way, the specificity for rejection increased up to 90 % when eight to ten IL-2R-positive lymphocytes were seen along with a TCI of ≥ 2.5. There was no further increase in specificity after that. A specificity index of 100 % for rejection could be obtained for moderate levels of both ICAM-1 (70% or more tubular cells) and IL-2R (eight or more lymphocytes). ICAM-1 expression in 70 % or more tubular cells and/or IL-2R expression in eight or more lymphocytes was found in 58 % of the FNAC aspirates with a TCI between 2.5 and 2.9. In conclusion, the expression of IL-2R in lymphoid cells and ICAM-1 in tubular cells was upregulated during rejection episodes and the upregulation preceded both the clinical and the routine FNAC diagnosis of rejection by 1 week. The ddition of these markers to the FNAC increased substantially the specificity of the FNAC to diagnose rejection.