OR16 Antibodies to donor human leukocyte antigen induce exosomes containing tissue-restricted self-antigens in acute and chronic rejection

Abstract

Aim Immune responses to tissue-restricted self-antigens (SAgs) are known contributors to acute and chronic rejection in solid organ transplantation (Tx). The goal of this study was to determine whether a donor-specific antibody (DSA) induces exosomes during lung and kidney allograft rejection and to define its antigenic compositions. Methods Exosomes were isolated from sera and bronchoalveolar lavage (BAL) of lung Tx recipients with acute or chronic rejection who developed both DSA and antibodies to SAgs, and from sera of kidney Tx recipients with transplant glomerulopathy (TG) who developed both DSA and antibodies to kidney-associated SAgs. The exosomes were isolated by ultracentrifugation, and then purified by the sucrose cushion method. Expression of lung-associated SAgs Collagen-V and K α 1-tubulin was examined by immunogold labelling and visualized by transmission electron microscopy. The presence of lung-associated SAgs and kidney-associated SAgs (i.e., Collagen-IV, fibronectin), and exosome-specific marker annexin-V was detected by Western immunoblot. Results Exosomes isolated from patients with acute rejection, chronic rejection, and TG showed the presence of tissue-restricted SAgs. Lung-associated SAgs Collagen-V and K α 1-tubulin were confirmed on the surface of exosomes. Exosomes with Collagen-V were detectable in exosomes isolated from sera just 1 month after lung Tx in all patients with acute rejection, much earlier than it could be diagnosed clinically (i.e., 3 months). Similarly, exosomes from sera in patients with bronchiolitis obliterans syndrome contained Collagen-V 6 months after lung Tx, before clinical diagnosis was possible. Exosomes from patients with TG had significantly higher expression of kidney-associated SAgs compared with the stable group. Conclusions The exosomes isolated from lung Tx recipients with acute and chronic rejection who developed DSA and antibodies to lung-associated SAgs and from kidney Tx recipients with TG confirm the presence of tissue-restricted SAgs in these patients, while the respective stable control groups do not. We therefore conclude that antibodies to human leukocyte antigen after lung or kidney Tx induce exosomes containing SAgs, which may result in the spread of immune response to tissue-restricted SAgs. T. Mohanakumar: Grant/Research Support; Company/Organization ; NIH R21AI123034 .