Phenotype, function, and differentiation potential of human monocyte subsets

• Published in: PloS one Vol. 12; no. 4; p. e0176460
• Main Authors: Boyette, Lisa B, Macedo, Camila, Hadi, Kevin, Elinoff, Beth D, Walters, John T, Ramaswami, Bala, Chalasani, Geetha, Taboas, Juan M, Lakkis, Fadi G, Metes, Diana M
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 26.04.2017; Public Library of Science (PLoS)
• Subjects: Animal models; Antigen-presenting cells; Autoimmune diseases; Bioindicators; Biology and Life Sciences; Blood; Bone marrow; Cadmium; Cancer; CD14 antigen; CD16 antigen; CD34 antigen; CD4 antigen; Cell activation; Cell Differentiation - drug effects; Cell lineage; Cell proliferation; Cells, Cultured; Colony-stimulating factor; Cytotoxicity; Defensive behavior; Dendritic cells; Dendritic Cells - cytology; Dendritic Cells - immunology; Dendritic Cells - metabolism; Disease; Engineering; Gene expression; Genetic aspects; Genotype & phenotype; Granulocyte-macrophage colony-stimulating factor; Granulocyte-Macrophage Colony-Stimulating Factor - pharmacology; Heterogeneity; Homeostasis; Humans; Immunology; Immunophenotyping; Infections; Inflammation; Interleukin 3; Interleukin-1beta - metabolism; Interleukin-6 - metabolism; Ligands; Lymphocytes T; Macrophage colony stimulating factor; Macrophage Colony-Stimulating Factor - pharmacology; Macrophages; Macrophages - cytology; Macrophages - immunology; Macrophages - metabolism; Medicine; Medicine and Health Sciences; Mice; Microscopy, Fluorescence; Monocytes; Monocytes - cytology; Monocytes - metabolism; Nucleic acids; Organs; Pathogens; Phagocytosis - drug effects; Phenotype; Polarization; Research and Analysis Methods; Subpopulations; Surgery; T cell receptors; T cells; Tissues; Toll-Like Receptors - agonists; Toll-Like Receptors - metabolism; Transplantation; Tumor Necrosis Factor-alpha - metabolism; Urinary bladder; Viral infections; United States > US; Pittsburgh Pennsylvania
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0176460

Human monocytes have been grouped into classical (CD14++CD16-), non-classical (CD14dimCD16++), and intermediate (CD14++CD16+) subsets. Documentation of normal function and variation in this complement of subtypes, particularly their differentiation potential to dendritic cells (DC) or macrophages, remains incomplete. We therefore phenotyped monocytes from peripheral blood of healthy subjects and performed functional studies on high-speed sorted subsets. Subset frequencies were found to be tightly controlled over time and across individuals. Subsets were distinct in their secretion of TNFα, IL-6, and IL-1β in response to TLR agonists, with classical monocytes being the most producers and non-classical monocytes the least. Monocytes, particularly those of the non-classical subtype, secreted interferon-α (IFN-α) in response to intracellular TLR3 stimulation. After incubation with IL-4 and GM-CSF, classical monocytes acquired monocyte-derived DC (mo-DC) markers and morphology and stimulated allogeneic T cell proliferation in MLR; intermediate and non-classical monocytes did not. After incubation with IL-3 and Flt3 ligand, no subset differentiated to plasmacytoid DC. After incubation with GM-CSF (M1 induction) or macrophage colony-stimulating factor (M-CSF) (M2 induction), all subsets acquired macrophage morphology, secreted macrophage-associated cytokines, and displayed enhanced phagocytosis. From these studies we conclude that classical monocytes are the principal source of mo-DCs, but all subsets can differentiate to macrophages. We also found that monocytes, in particular the non-classical subset, represent an alternate source of type I IFN secretion in response to virus-associated TLR agonists.