Early ultrastructural changes in renal allografts: correlation with antibody-mediated rejection and transplant glomerulopathy

Abstract

Transplant glomerulopathy (TG) is associated with antibody-mediated renal allograft rejection (AMR) and reduced graft survival. Histologically, TG is typically seen >1 year posttransplantation. However, ultrastructural changes including glomerular endothelial swelling, subendothelial widening and early glomerular basement membrane duplication are associated with development of TG but appear much earlier. We examined the specificity of these changes for AMR, and whether these are inevitably associated with development of TG. Of 98 for cause renal allograft biopsies carried out within 3 months of transplantation with available serologic data, 17 showed C4d-positive AMR and 16 had histologic changes of AMR and donor-specific antibodies (DSA), but no C4d. All three ultrastructural changes were seen in 11 of 17 biopsies with C4d-positive AMR, 8 of 16 with histologic changes of AMR and DSA but no C4d, and 0 of 65 without histologic changes of AMR and/or DSA (p < 0.0001 for both of the former groups vs. the latter). Twenty patients with positive DSA (18 with histologic changes of AMR and 11 C4d-positive) had ≥1 follow-up biopsy; eight developed overt TG 3.5-30 months posttransplantation. Among the 18 patients with DSA and histologic changes of AMR, 11 C4d-positive and 7 C4d-negative, treatment for AMR after the early biopsy significantly reduced subsequent development of overt TG.