An unbiased, high-dimensional characterization of the myeloid compartment using mass cytometry is described in the journal Nature Immunology (10.1038/ni.3006, 2014).

Markers currently used to define myeloid cells are expressed by several cell types, and their expression may be altered by the inflammatory environment. Moreover, flow cytometry–based analyses are hampered by the number of parameters that can be analyzed and by overlap between channels. Mass cytometry makes use of heavy metal isotypes as tags, permitting analysis of many parameters at a single-cell level and discrimination between related cell types.

Burkhard Becher, Evan Newell and their colleagues used mass cytometry and a 38-antibody panel to analyze myeloid cells within lymphoid and nonlymphoid tissue under steady-state conditions. Using automated approaches, they identify several myeloid cell subsets, revealing the considerable phenotypic diversity among these cells. Although myeloid cells are heterogeneous and their phenotype differs on the basis of the resident tissue, most clusters were composed of cells from different tissues. However, brain microglia and lung alveolar macrophages formed a single cluster, whereas neutrophils were diverse. A comparison between Csf2rb-deficient and wild-type mice revealed a loss in alveolar macrophages, eosinophils and some dendritic cell populations in the Csf2rb-deficient mice, confirming prior reports, and an unexpected reduction in CD11blo natural killer cells.

These findings validate this unbiased approach to segregate and classify immune cell types and provide a useful resource for future studies.