Pathologic Characteristics of Early or Late Acute Cellular Rejection and Outcome After Kidney Transplant

Objectives: To determine the pathologic features of early- and late-onset acute cellular rejection that may contribute to graft loss after kidney transplant. Materials and Methods: There were 247 patients who had acute cellular rejection included in the study. The biopsy that showed the highest acute cellular rejection severity was evaluated for each patient (total, 247 biopsies) and classified as early (time of biopsy, <= 6 mo) or late (time of biopsy, > 6 mo) acute cellular rejection. Results: The mean scores of interstitial inflammation (interstitial inflammation and tubulitis), scarring (interstitial fibrosis/tubular atrophy), and vascular disorders (arteriolar hyaline thickening and vascular intimal fibrosis) were significantly higher in late than early acute cellular rejection. Death-censored graft survival at 8 years after kidney transplant was higher in patients who had early (88%) than late acute cellular rejection (66%; P <= .001). Early and late acute cellular rejection with either low- or high-grade interstitial fibrosis/tubular atrophy had similar death-censored graft survival. In patients who had late acute cellular rejection, death-censored graft survival was significantly higher when there was low- (survival; 79%) than high-grade vascular intimal fibrosis (survival, 48%; P <= .006). Long-term graft loss was significantly associated with the number of biopsies, intimal arteritis, and tubulitis in patients who had early acute cellular rejection, and vascular intimal fibrosis in patients who had late acute cellular rejection. Conclusions: High-grade vascular intimal fibrosis was a risk factor for poor long-term graft survival in late acute cellular rejection after kidney transplant.