Background: Circulating exosomes isolated from lung transplant recipients (LTxRs) with acute or chronic rejection contains lung self-antigens (SAgs), K alpha 1 tubulin (Kα1T) and collagen V (Col-V), and have been proposed to play a role in inducing immune responses leading to rejection. The goal of this study is to determine whether primary graft dysfunction (PGD), a known risk factor for rejection, will lead to exosome induction from the transplanted lungs and to determine the role of persistence of the exosomes in the clinical course.

Methods: Ten LTxRs with grade 3 PGD and 5 without PGD (ISHLT criteria) were included in this study. Sera were collected 48hrs following LTx and at 30 days, exosomes were isolated using the ultracentrifugation method. Purity of the exosomes was assessed by western blot using CD9 and electron microscopy. Exosomes isolated from sera at 48hrs were characterized for SAgs (Kα1T, Col-V), MHC class II molecule and CIITA, transcription factors (NF-kB, HIF-1α), Adhesion molecules (ICAM, VCAM), co-stimulatory molecules (CD80-86), and alpha subunit of 20S-proteasome using western blot. We also isolated exosomes from all PGD 3 LTxRs on day 30.

Results: Exosomes isolated from sera of PGD 3 LTxRs demonstrated increased levels of SAgs in comparison to PGD grade 0 LTxR (1.4 fold increase in Col-V (p=0.06) and 1.7 fold increase in Ka1T (p=0.04)). The exosomes also contained increased levels of MHC class II (6.6 fold increase p<0.001), CIITA (4.3 fold increase p<0.001) along with adhesion molecules (6.9 and 4 fold increase in ICAM and VCAM p<0.001), transcription factors (0.8 and 6.9 fold increase HIF-1α and NFkB (p<0.001)) and co-stimulatory molecules (6.6fold increase in CD80 and 7 fold increase in CD86 (p<0.001)) and 20S proteasome (2.4 fold increase p=0.01). Exosomes isolated on day 30 from PGD 3 LTxRs containing SAgs decreased significantly in 8/10 LTxRs (3.7 fold decrease in Col-V p=0.002 and 2.3 fold decrease in Ka1T p=0.04).

Conclusion: Our preliminary analysis demonstrated that PGD 3 following LTxRs leads to induction of circulating exosomes with SAgs, immunoregulatory proteins. Ongoing studies will determine the clinical significance of persistence of circulating exosomes.

CITATION INFORMATION: Sharma M., Biswas Roy S., Walia R., Omar A., Bremner R., Smith M., Mohanakumar T. Circulating Exosomes with Lung Self-Antigens, Kα1Tubulin and Collagen V, and Immune Regulatory Proteins in Lung Transplant Recipient with Primary Graft Dysfunction Am J Transplant. 2017;17 (suppl 3).

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