Background and Objective: Plasma cells are known as the final effectors of humoral immune response. Their significance and clinical outcomes are still controversial in kidney transplantation. They have been associated with humoral rejection and C4d positivity as with T cell mediated rejection. The aim of the study was to review all possible clinical-pathological characteristics associated with plasma cell infiltrate.

Methods: We performed a retrospective and descriptive study that reviewed all kidney transplantation biopsies with plasma cell infiltration (n=57) between 1990 and 2012 in our Center. Banff criteria was used for histological evaluation.

Results: Biopsies were split in four main histological groups: Acute Cellular Rejection (ACR; n=27), Acute Antibody Mediated Rejection (AAMR;n=5), Polyomavirus Nephropathy (PN; n=3), and Acute Interstitial Nephritis (AIN; n=7) due to pyelonephritis. Fifteen patients had other diagnosis and were not considered for this analysis. There was no significant difference among all groups in demographics, donor type, sensitization and HLA matching. Underexposure to immunosuppression such as low adherence or drug conversion were observed in 55% of the patients in the ACR group, 40% in AAMR group, 33% in PN group and 83% in AIN group. The mean time from transplant to the biopsy was predominantly late in all groups (36±34 months) except for PN (11±4 months). In AAMR and PN groups all patients who presented plasma cell infiltration lost their graft. In ACR and AIN groups the plasma infiltration was associated with graft loss in 37% and 29% respectively. Kaplan-Meier analysis (Log-rank=12.78, p=0.006) showed that graft survival was significant different between groups in five years, with ACR presenting 31% of graft loss and AAMR presenting worse survival with 100% of graft loss.

Conclusion:ACR was the main diagnosis associated with plasma cell infiltrate (47%). Underexposure of immunesupression was frequent in all groups. Plasma cell presence was associated with a poor prognosis, especially in antibody mediated rejection and polyomavirus nephropathy. Further analysis of plasma cell infiltrate intensity and local physiopathological mechanisms are necessary to determine their real functional role in different histological conditions.

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