Acute Rejection Phenotypes in the Current Era of Immunosuppression: A Single-Center Analysis

BACKGROUND: Besides ‘definitive rejection’, the Banff classification includes categories for ‘suspicious for rejection’ phenotypes. The aim of this study was to determine the frequency and phenotypes of rejection episodes in 316 consecutive renal transplants from 2009 to 2014 grouped into patients without/with pretransplant HLA-DSA (ptDSA(neg), n = 251; ptDSA(pos), n = 65). METHODS: All adequate indication (n = 125) and surveillance biopsies (n = 538) performed within the first year posttransplant were classified according to the current Banff criteria. RESULTS: ‘Suspicious for rejection’ phenotypes were 3 times more common than ‘definitive rejection’ phenotypes in biopsies from ptDSA(neg) patients (35% vs 11%) and equally common in biopsies from ptDSA(pos) patients (25% vs 27%). In both groups, ‘suspicious for rejection’ phenotypes were more frequent in surveillance than in indication biopsies (28% vs 16% in ptDSA(neg) patients, and 37% vs 29% in ptDSA(pos) patients). ‘Borderline changes: ‘Suspicious' for acute T-cell mediated rejection’ (91%) were the dominant ‘suspicious for rejection’ phenotype in ptDSA(neg) patients, whereas ‘borderline changes’ (58%) and ‘suspicious for acute/active antibody-mediated rejection’ (42%) were equally frequent in biopsies from ptDSA(pos) patients. Inclusion of ‘suspicious for rejection’ phenotypes increased the 1-year incidence of clinical (ptDSA(neg) patients: 18% vs 8%, P = 0.0005; ptDSA(pos) patients: 24% vs 18%, P = 0.31) and (sub)clinical rejection (ptDSA(neg) patients: 59% vs 22%, P < 0.0001; ptDSA(pos) patients: 68% vs 40%, P = 0.004). CONCLUSIONS: ‘Suspicious for rejection’ phenotypes are very common in the current era and outnumber the frequency of ‘definitive rejection’ within the first year posttransplant.