Molecular Evidence of Chronic Cellular Rejection in C4d and Microvascular Inflammation Negative Transplant Glomerulopathy

Transplant glomerulopathy (TGP) is frequently found in the setting of chronic antibody mediated rejection along with microvascular inflammation (MVI) (peritubular capillaritis+glomerulitis score > 1) and/or positive c4d staining. We assessed the molecular profiles of TGP in the absence of microvascular inflammation and C4d staining as compared to TGP with positive MVI and/or C4d. Gene expression profiles of TGP in the absence of microvascular inflammation and C4d lack molecular features of antibody-mediated rejection but suggest chronic cellular rejection. 44 for-cause renal allograft biopsies were studied using Affymetrix HuGene 1.0 ST expression arrays; 12 with normal biopsy findings (G1), 17 with a diagnosis of TGP, C4d positive and/or a MVI score >1 (G2), and 10 with a diagnosis of TGP and C4d negative and MVI score <=1 which were DSA negative (G3A) and 5 TGP and C4d negative and MVI score <=1 (G3B).