What are the banff criteria for AMR/humoral rejection?
• Acute AMR: Defined by detection of DSA, C4d staining on the biopsy, and allograft pathology consistent with this diagnosis of AMR. The 2013 Banff Conference changed the definition of AMR. It acknowledges that C4d staining may be negative in AMR, termed C4d negative AMR. In this setting, there are other pathological changes, including intimal arteritis, peritubular capillaritis, and glomerulitis in the setting of positive DSA.
• Chronic AMR/TG: Defined by the Banff histological term chronic glomerulopathy (CG). CG is the double contouring of the glomerular basement membrane seen on light or electron microscopy. This is a result of repetitive episodes of endothelial activation, injury, and repair leading to pathological changes of the glomerular basement membrane. TG risk factors include preexisting or de novo anti-HLA antibodies, Hepatitis C infection, and thrombotic microangiopathy. TG prevalence is 5% to 20% in most series, reaching 55% in some high-risk cohorts, and is associated with worse allograft outcomes. Kidney transplant biopsy is the gold standard for diagnosis of TG. One has to be vigilant, as the Scr may not rise until considerable damage is done. A rising level of proteinuria several years after transplant is an indication for kidney transplant biopsy, as this can be sign of developing TG.