Clinical and pathological analyses of chronic vascular rejection after kidney transplantation

Clinicopathological Analyses of Chronic Renal Allograft Arteriopathy after Kidney Transplantation

INTRODUCTION

Herein, we discuss clinicopathological analyses of cases of chronic renal allograft arteriopathy (CRA) after renal transplantation and clarify the mechanisms underlying the development and prognostic significance of CRA.

METHODS

CRA was diagnosed in 34 renal allograft biopsy specimens (BSs) obtained from 27 renal transplant patients who were followed up at the Department of Urology and Transplant Surgery, Toda Chuo General Hospital, between January 2010 and December 2020.

RESULTS

CRA was diagnosed at a median of 33.4 months post-transplantation. Of the 27 patients, 16 had a history of rejection. Among the 34 BSs showing evidence of CRA, CRA was mild (cv1 in Banff's classification) in 22, moderate (cv2) in 7, and severe (cv3) in 5 patients. We then classified the 34 BSs showing evidence of CRA based on their overall histopathological features as follows: cv alone seen in 11 (32%) BSs, cv + antibody-mediated rejection (AMR) in 12 (35%), and cv + T-cell-mediated rejection (TCMR) in 8 (24%). Loss of the renal allograft occurred during the observation period in 3 patients (11%). Of the remaining patients with functioning grafts, deterioration of renal allograft function after biopsies occurred in 7 cases (26%).

CONCLUSIONS

Our study results suggest that AMR contributes to CRA in 30-40% of cases, TCMR in 20-30% of cases, isolated v lesions in 15% of cases, and cv lesions alone in 30%. The intimal arteritis was a prognostic factor in CRA.

Clinicopathologic Analyses of Chronic Vascular Rejection After Kidney Transplantation

AIM

We discuss the clinicopathologic analyses of cases of biopsy specimens (BS) after renal transplantation and clarify the mechanisms underlying the development and prognostic significance of chronic vascular rejection (CVR).

PATIENTS

CVR was diagnosed in 30 renal allograft BS obtained from 23 renal transplant patients being followed up at the Department of Urology and Transplant Surgery, Toda Chuo General Hospital, between January 2010 and August 2017.

RESULTS

CVR was diagnosed at a median of 33.1 months post-transplantation. Among the 23 patients, 14 had a history of rejection. Among the 30 BS showing evidence of CVR, the CVR was mild (cv1 on Banff's classification) in 19, moderate (cv2) in 6, and severe (cv3) in 5. We then classified the 30 BS showing evidence of CVR by their overall histopathologic features as follows: cv alone was seen in 9 (30%), cv + antibody-mediated rejection (AMR) in 11 (37%), and cv + T-cell-mediated rejection (TCMR) in 8 (27%). Loss of the renal allograft occurred during the observation period in 2 patients (9%). Of the remaining patients with functioning grafts, deterioration of the renal allograft function after the biopsies occurred in 6 (26%).

CONCLUSIONS

Our study results suggest that AMR contributes to CVR in 30% to 40% of cases, TCMR in 20% to 30% of cases, isolated v lesions in 10% of cases, and cv lesions alone in 30%. The prognosis of the graft exhibiting CVR was not too poor even under the present immunosuppressive protocol.

Cell mediated rejection revisited: Past, current, and future directions

The Banff histopathology classification system is the gold standard for assessing the causes of kidney allograft dysfunction triggered by antibody-mediated and T-cell-mediated immune reactions, thereby providing mechanistic insight and guiding therapeutic decisions. The original Banff classification (1993) consisted of four histological categories representing cell-mediated rejection: interstitial inflammation (i), tubulitis (t), endoarteritis (v), and transplant glomerulitis (g). The revised Banff 2007 classification added total inflammation score (ti) from both scarred and unscarred areas based on evolving interpretations of interstitial infiltrates. Further reappraisal of cell-mediated interstitial inflammation led to the introduction of a new inflammation score specific for areas of interstitial fibrosis and tubular atrophy, termed i-IF/TA, in the Banff 2015 scheme, establishment of a new Banff working group on T-cell-mediated rejection (TCMR), and revised criteria of chronic active TCMR in Banff 2017 classification. These Banff scheme updates reflect the general recognition that chronic interstitial inflammation is a common denominator of poor kidney allograft outcome. However, revised theories on the pathogenic importance of interstitial infiltrates have created difficulties in interpretation of chronic tubulointerstitial inflammation, as there are currently no histological criteria to discriminate immune-mediated tissue injury from 'non-specific' injury. Evolving theories on vascular lesions, both active and chronic, have also complicated histological assessment by obscuring the distinction between antibody-mediated and T-cell-mediated tissue injury. This review provides an overview of recent ideas on interstitial inflammation and vascular lesions based on emerging concepts of T-cell-mediated rejection.