Fig. 2. Specific monocyte clusters are associated with ambient exposure to PM2.5 levels in healthy versus asthmatic subjects. Computational analysis was performed on mass cytometry data from PBMCs from 6-8 years old subjects exposed to low versus high PM2.5 (N=25 including 15 healthy and 10 asthmatic subjects per group). Eight unsupervised distinct clusters were identified using FlowSOM based on expression of phenotypic and functional monocyte markers. Heatmap representing expression intensity of each marker and the frequency of monocyte clusters (A). Data visualization using Uniform Manifold Approximation and Projection (UMAP) for dimension reduction demonstrated the neighborhood pattern of monocyte clusters. The colors in the UMAP correspond to the colors of the cluster IDs, as indicated in the heatmap. (B). Non-parametric statistical analysis identified monocyte signatures significantly associated with exposure to PM2.5 in children diagnosed with or without asthma (C). P values, computed using non-parametric Wilcoxon-rank sum test, indicate significance of difference in frequency of circulating monocyte clusters from children exposed to low and high levels of PM2.5.