Date of Award

2021

Embargo Period

8-5-2025

Document Type

Dissertation - MUSC Only

Degree Name

Doctor of Philosophy (PhD)

Department

Molecular and Cellular Biology and Pathobiology

College

College of Graduate Studies

First Advisor

Carl Atkinson

Second Advisor

Philip Howe

Third Advisor

Amanda Larue

Fourth Advisor

Shikhar Mehrotra

Fifth Advisor

Stephen Tomlinson

Sixth Advisor

Chenthamarakshan Vasu

Abstract

Lung transplant (LTx) patients have the lowest long-term survival rates compared to other solid organ transplants. The complications after LTx such as primary graft dysfunction (PGD) and ultimately chronic lung allograft dysfunction (CLAD) are the main reasons for poor survival. A large number of risk factors such as underlying pulmonary disease diagnosis, age, donor and recipient cigarette smoking history, and the severity of ischemia reperfusion injury (IRI) have all been associated with increased risk of post-LTx complications and poor outcome. Historically, humoral and cellular alloimmune responses have long been the focus of immune-related graft injury. However, in recent years, the contribution of humoral and cellular autoimmune responses to graft injury and transplant outcome has come to light. Lung-specific autoantibodies that recognize non-HLA antigens and autoreactive lymphocytes have been hypothesized to contribute to graft injury and have been correlated with PGD, CLAD, and survival. Mounting evidence suggests that autoimmunity can develop during pulmonary disease progression before LTx and may influence alloreactive and autoreactive immune responses following LTx. The goal of these proposed studies is to demonstrate that pre-existing autoimmunity predisposes to exacerbated graft injury and leads to worse outcomes. We first examined the relationship between autoantibodies and PGD development. We accomplished this goal by characterizing the circulating antibody landscape in a cohort of COPDLTx patients that did or did not develop PGD. We measured total immunoglobulin levels and circulating elastin and collagen autoantibody levels pre- and post-LTx. No significant differences were seen in total, elastin, or collagen IgM, IgG, IgG1, IgG2, IgG3, and IgG4 antibodies between PGD+ and PGD- recipients. Antibody function can be greatly altered by glycosylation changes to the antibody Fc region and recent studies have reported altered IgG glycosylation profiles in COPD patients. We therefore utilized a novel mass spectrometry-based multiplexed N-glycoprotein imaging approach and measured changes in IgG-specific antibody N-glycan structures. COPD-LTx recipients who developed PGD had significantly increased IgG1 N-glycan signatures as compared PGD- recipients. We show that immunoglobulin and autoreactive antibody levels are not significantly different in COPD LTx recipients that develop PGD. However, using a novel IgG glycomic analysis we were able to demonstrate multiple significant increases in IgG1 specific N-glycan signatures that were predictive of PGD development. Taken together, these data represent a potential novel method for identifying COPD patients at risk for PGD development and may provide clues to mechanisms by which antibody N-glycan signatures could contribute to antibody-mediated PGD pathogenesis. In the second aspect of our studies, we examined how recipient CS exposure impacts autoreactive-mediated graft damage. CS exposure has previously been implicated in exacerbating IRI and LTx outcome. Using a chronic CS-exposure mouse model of emphysema and a syngeneic orthotopic left LTx model, we were able to assess the contribution of pre-existing autoimmunity specifically on autoreactive-mediated graft injury. We were able to demonstrate that recipient pre-LTx CS exposure promotes an exacerbated pro-inflammatory immune response thereby inducing severe autoreactive-mediated graft injury, autoantibody production, and IL-17 production. These data suggest that recipient CS-exposure predisposes LTx patients to a more sever autoreactive immune response. Previous work from our lab and others proposed that complement activation is a key component in IRI and autoantibody-mediated graft injury. Therefore, we utilized a novel, bifunctional injury-site natural antibody targeted complement inhibitor, C2scFv-Crry, to assess the contribution of complement in CS-mediated graft damage and the efficacy of acute complement inhibition on reducing autoreactive-mediated graft damage. We found that acute complement inhibition significantly reduced CS-associated inflammation, graft injury, and autoantibody production. These results suggest that complement plays a central role in promoting autoreactive-mediated graft injury and demonstrate the efficacy of a novel complement inhibitor to reduce CS-associated autoreactive-mediated graft damage. Altogether, the data presented here show the deleterious effects of pre-existing autoimmunity in LTx graft injury and suggest that acute complement inhibition may be a promising therapeutic intervention strategy to reduce autoreactive-mediated graft damage.

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Available for download on Tuesday, August 05, 2025

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