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 researchers at Cedars-Sinai Medical Center explored the possibility of predicting the risk for ABMR by measuring mRNA transcripts of ABMR-associated genes in plasma exosomes from kidney transplant patients.
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.
Among 21 candidate genes, the researchers identified multiple genes (gp130, CCL4, TNFα, 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, TNFα and CCL4 was significantly higher in the ABMR than the CMR (p<0.0001) and no rejection control groups (p<0.01 vs. DES control, p<0.05 vs. non-DES control).
These results suggest that plasma exosomes may contain information indicating clinical conditions of kidney transplant patients. mRNA transcript profiles based on gp130, SH2D1B, TNFα and CCL4 in plasma exosomes may be utilized to predict on-going and/or imminent ABMR.
Gene scores among 4 patient groups and ROC curve of gene score
A: Differential gene score based on the mRNA transcript levels of 4 selected genes (gp130, SH2D1B, TNFα and CCL4) in plasma exosomes among ABMR, CMR, DES Control, and non-DES Control patient groups. Horizontal long and short lines indicate mean ± standard deviation of results of 18 ABMR, 8 CMR, 18 DES Control and 20 non-DES Control patients, respectively. Statistical analysis results by MW test: ** p<0.01, * 0.01≤p<0.05. B: ROC curve of gene score.