Plasma Exosomes from HLA-Sensitized Kidney Transplant Recipients Contain mRNA Transcripts Which Predict Development of Antibody-Mediated Rejection.

Background: Sensitization to human leukocyte antigens (HLA) remains a significant immunologic barrier to successful transplantation. Identifying immune mechanisms responsible for antibody-mediated rejection (ABMR) is an important goal. Here we explored the possibility of predicting the risk for ABMR by measuring mRNA transcripts of ABMR-associated genes in plasma exosomes from kidney transplant patients. Methods: Total RNA was extracted from exosomes purified from 152 EDTA-plasma samples of 64 patients (18 ABMR, 8 cell-mediated rejection [CMR], 38 no rejection in desensitized (DES) and non-desensitized (non-DES) control groups) for reverse transcription into cDNA, preamplification and then real time quantitative polymerase chain reaction (qPCR) for 21 candidate genes. The mRNA transcript levels of each gene were calculated. Comparisons were made among 4 patient groups for each gene and also for a gene combination score based on selected genes. Results: Among 21 candidate genes, we identified multiple genes (gp130, CCL4, TNF[alpha], SH2D1B, CAV1, DARC) whose mRNA transcript levels in plasma exosomes significantly increased among ABMR compared to CMR and/or control patients. A gene combination score calculated from 4 genes of gp130, SH2D1B, TNF[alpha] and CCL4 was significantly higher in the ABMR than the CMR (p

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