High-Content Immunophenotyping and Hierarchical Clustering Reveal Sources of Heterogeneity and New Surface Markers of Human Blood Monocyte Subsets

Objective Blood monocyte subsets are emerging as biomarkers of cardiovascular inflammation. However, our understanding of human monocyte heterogeneity and their immunophenotypic features under healthy and inflammatory conditions is still evolving. Rationale In this study, we sought to investigate the immunophenome of circulating human monocyte subsets. Methods Multiplexed, high-throughput flow cytometry screening arrays and computational data analysis were used to analyze the expression and hierarchical relationships of 242 specific surface markers on circulating classical (CD14++CD16−), intermediate (CD14++CD16+), and nonclassical (CD14+CD16++) monocytes in healthy adults. Results Using generalized linear models and hierarchical cluster analysis, we selected and clustered epitopes that most reliably differentiate between monocyte subsets. We validated existing transcriptional profiling data and revealed potential new surface markers that uniquely define the classical (e.g., BLTR1, CD35, CD38, CD49e, CD89, CD96), intermediate (e.g., CD39, CD275, CD305, CDw328), and nonclassical (e.g., CD29, CD132) subsets. In addition, our analysis revealed phenotypic cell clusters, identified by dendritic markers CMRF-44 and CMRF-56, independent of the traditional monocyte classification. Conclusion These results reveal an advancement of the clinically applicable multiplexed screening arrays that may facilitate monocyte subset characterization and cytometry-based biomarker selection in various inflammatory disorders.