Borderline rejection in ABO-incompatible kidney transplantation.

Area of Science:

• Nephrology
• Transplant Surgery
• Immunology

Background:

• Clinical outcomes for ABO-incompatible (ABOi) and ABO-compatible (ABOc) kidney transplantation (KT) are comparable.
• Protocol kidney biopsies (PKB) in ABOi KT recipients often show C4d positivity without overt antibody-mediated rejection (ABMR), but histologic progression remains unclear.

Purpose of the Study:

• To evaluate histologic parameters in PKB at 12 months post-transplant.
• To compare clinical outcomes at 1 year between ABOi and ABOc kidney transplant recipients.
• To investigate the histologic progression in ABOi kidney transplants.

Main Methods:

• A prospective observational study was conducted from 2009 to 2013.
• 146 ABOc and 30 ABOi living-donor KT recipients underwent PKB and indication biopsies.
• ABOi recipients received a desensitization protocol including rituximab, plasma exchange/immunoadsorption, and immunoglobulins.

Main Results:

• At 1 year, PKB revealed significantly more borderline rejection lesions in the ABOi group (23.3%) compared to the ABOc group (6.8%).
• C4d positivity was more frequent in the ABOi group (P=.001).
• No significant differences were observed in T-cell-mediated rejection, ABMR, interstitial fibrosis and tubular atrophy (IFTA), or transplant glomerulopathy between the groups at 1 year.

Conclusions:

• Protocol kidney biopsies at 1 year in ABOi kidney transplant recipients show an increased incidence of borderline lesions, irrespective of ABO titers, HLA incompatibility, or donor-specific antibodies.
• These borderline lesions do not correlate with increased rates of IFTA or transplant glomerulopathy.
• No significant clinical differences in outcomes were observed between ABOi and ABOc kidney transplant recipients at 1 year.