Banff 2013 Meeting Report: Inclusion of C4d-Negative Antibody-Mediated Rejection and Antibody-Associated Arterial Lesions

Banff 2013 acknowledges C4d negative antibody-mediated rejection (ABMR). Positive C4d staining in graft biopsy was relegated to just 1 of 3 evidence of current/recent antibody interaction with vascular endothelium. The remaining 2 are moderate microvascular inflammation (g+ptc score at least 2) and the increased expression of gene transcripts related to endothelial injury. The other two criteria for acute/active and chronic active ABMR are intact with addition of intimal arteritis as one of histology evidence of acute tissue injury in acute ABMR.

The definition for glomerulitis (g) was changed. Now required complete or partial occlusion of glomerular capillary lumens and endothelial swelling in >1 capillary. The threshold for transplant glomerulopathy is modified. However, interstitial mononuclear cell infiltrate in scarred tissue (ti) is still not included in criteria for diagnosis of T cell-mediated rejection. Though it was recommended to included in the biopsy report.

Eliminating borderline rejection

According to Banff classification, borderline rejection in kidney allografts exist as an entity between no acute rejection and acute cellular or T cell-mediated rejection type IA. Its criteria were arbitrarily set with mild tubulitis (t score equal to or less than 1) and/or mild interstitial mononuclear cell infiltrate (i score equal to or less than 1). Borderline rejection is problematic because it does not tell whether rejection is occurring in the grafts. Acute tubular necrosis, a common cause of delayed graft function, can also have similar histologic features.