Neutrophil Subset Immunophenotyping.

Neutrophils, the most abundant circulating leukocyte population, are principally involved in pathogen clearance through three major mechanisms: phagocytosis, degranulation, and release of neutrophil extracellular traps. Along with these roles, neutrophils can promote or suppress tumor growth and metastatic processes. These different immunological functions reflect a great heterogeneity of maturation and activation status, as at least two main circulating populations can be identified: low-density granulocytes and normal-density neutrophils. In this chapter, we provide a detailed protocol for multiparametric flow cytometry immunophenotyping of circulating and bone marrow neutrophil subsets, as well as recommendations for protocol optimization, troubleshooting, and clinical sample analysis.