Abstract
BackgroundAsthma has been associated with impaired interferon response. Multiple cell types have been implicated in such response impairment and may be responsible for asthma immunopathology. However, existing models to study the immune response in asthma are limited by bulk profiling of cells. Our objective was to Characterize a model of peripheral blood mononuclear cells (PBMCs) of patients with severe asthma (SA) and its response to the TLR3 agonist Poly I:C using two single-cell methods.MethodsTwo complementary single-cell methods, DropSeq for single-cell RNA sequencing (scRNA-Seq) and mass cytometry (CyTOF), were used to profile PBMCs of SA patients and healthy controls (HC). Poly I:C-stimulated and unstimulated cells were analyzed in this study.ResultsPBMCs (n = 9414) from five SA (n = 6099) and three HC (n = 3315) were profiled using scRNA-Seq. Six main cell subsets, namely CD4 + T cells, CD8 + T cells, natural killer (NK) cells, B cells, dendritic cells (DCs), and monocytes, were identified. CD4 + T cells were the main cell type in SA and demonstrated a pro-inflammatory profile characterized by increased JAK1 expression. Following Poly I:C stimulation, PBMCs from SA had a robust induction of interferon pathways compared with HC. CyTOF profiling of Poly I:C stimulated and unstimulated PBMCs (n = 160,000) from the same individuals (SA = 5; HC = 3) demonstrated higher CD8 + and CD8 + effector T cells in SA at baseline, followed by a decrease of CD8 + effector T cells after poly I:C stimulation.ConclusionsSingle-cell profiling of an in vitro model using PBMCs in patients with SA identified activation of pro-inflammatory pathways at baseline and strong response to Poly I:C, as well as quantitative changes in CD8 + effector cells. Thus, transcriptomic and cell quantitative changes are associated with immune cell heterogeneity in this model to evaluate interferon responses in severe asthma.
Highlights
Asthma has been associated with impaired interferon response
I:C stimulation identified antigen presentation heterogeneity in peripheral blood mononuclear cells (PBMCs) from severe asthmatics Given the decreased expression of antigen presentation genes in monocytes, we focused on cell-specific changes in phagocytosis and antigen presentation pathways compared to other cells
We found that CD4 + T cells demonstrated enrichment of antigen presentation genes; elements of antigen presentation pathways and phagocytosis were differentially expressed across cell types and disease status, with HLA-DRA, IGKC, and IGHM demonstrating low expression in cells from severe asthma (SA)
Summary
Asthma has been associated with impaired interferon response. Multiple cell types have been impli‐ cated in such response impairment and may be responsible for asthma immunopathology. Among environmental influences, increased susceptibility to viral infections is strongly associated with asthma, with several studies showing impairment in different components of the antiviral response [9, 13,14,15,16,17,18,19]. These studies have informed our understanding of asthma pathogenesis, we lack a comprehensive picture of functional and quantitative responses at the single-cell level in asthma, limiting our understanding of distinct cell subtypes’ contribution to specific disease endotypes
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