Asthma is common, affecting more than 300 million people worldwide. Though well controlled in most, a subset experience symptoms refractory to treatment, accounting for nearly half the US healthcare expenditure on asthma. Time-of-flight mass cytometry (CyTOF) offers an opportunity to characterize the inflammatory milieu of bronchoalveolar lavage (BAL) in unprecedented detail. Pairing this with gene expression data from bronchial epithelial cells (BECs) and BAL yields the most comprehensive understanding of SA to date.
Flow cytometry from 7 healthy control, 15 mild-to-moderate and 19 SA patients reveals 31 cells types. Network construction of covariant cells demonstrates neighborhoods that define 4 patient clusters. One SA-enriched cluster shows high levels of IFN-ɣ production driven by T-cells. Other clusters demonstrate varying abundance of innate immune lineages that differ in Type 2 (T2) cytokine elaboration. BEC gene expression analysis identifies 3 clusters, two of which enriched for SA cases. One SA-cluster demonstrates high levels of T2 inflammation and strong relationship with mast cell/basophils in BAL. Another shows low levels of T2 inflammation despite housing a third of SA patients. GSEA identifies interferon and IL-6 pathway activation, suggesting Type 1 (T1) immune response. These data were corroborated with transcriptional profiling of BAL cells, underscoring networks of interacting cytokines between cellular compartments.
Comprehensive immunophenotyping of BAL identifies stereotyped derangements associated with cytokine signatures and reciprocal epithelial response. Correlative mapping of receptor-cytokine pairings across BEC and BAL offers insight into pathways driving inflammation and may guide future targeted interventions.