Imaging Mass Cytometry to Assess the Pathobiology of Chronic Lung Allograft Dysfunction

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<h3>Purpose</h3> Long-term survival after lung transplantation remains limited, mostly because of Chronic Lung Allograft Dysfunction (CLAD), which has two main phenotypes: bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS). Our tools for assessing lung allograft cells are limited by lung tissue autofluorescence. We aimed to assess CLAD lung allografts using imaging mass cytometry (IMC), a mass spectroscopic technology that allows high-resolution, multi-dimensional characterization of lung cell surface and intracellular proteins at a single cell level, using heavy metal-tagged antibodies. <h3>Methods</h3> Explanted lung tissue was obtained at the time of retransplantation from one BOS and one RAS patient. One donor lung sample was used as control (figure 1A-C). Paraffin-embedded lung tissue was sectioned and stained with 24 heavy-metal-tagged antibodies selected to identify structural and immune proteins of interest. Three 1.5mm² regions of interest in each sample were ablated and data was analyzed using MCD viewer and HistoCAT software. <h3>Results</h3> Visualization of individual antibody binding patterns showed differences between samples, such as greater E-cadherin staining (epithelial cells) in airways of normal lung compared to those of CLAD (figures 1D-F). Spatial distribution of B and T cells within a lymphoid aggregate in the RAS sample is shown (figure 1G-J). We also used an exploratory tSNE strategy to create a 2D representation of cells clustered according to the similarity of their antibody-binding in 24-dimensional space (figure 1K). Precise localization of specific cell populations such as B cell and memory T cell subsets can then be achieved by first identifying them on the tSNE plot and then highlighting them on the IMC image (figures 1L-N). <h3>Conclusion</h3> Our results indicate that IMC is a powerful tool for precise localization of cells within lung tissue samples, allowing both hypothesis-driven comparisons as well as exploratory analyses.