slan/M-DC8+ cells constitute a distinct subset of dendritic cells in human tonsils

• Published in: Oncotarget Vol. 7; no. 1; pp. 161 - 175
• Main Authors: Micheletti, Alessandra, Finotti, Giulia, Calzetti, Federica, Lonardi, Silvia, Zoratti, Elisa, Bugatti, Mattia, Stefini, Stefania, Vermi, William, Cassatella, Marco A.
• Format: Journal Article
• Language: English
• Published: Impact Journals LLC 05.01.2016
• Subjects: Research Paper: Immunology
• ISSN: 1949-2553; 1949-2553
• DOI: 10.18632/oncotarget.6660

Human blood dendritic cells (DCs) include three main distinct subsets, namely the CD1c + and CD141 + myeloid DCs (mDCs) and the CD303 + plasmacytoid DCs (pDCs). More recently, a population of slan/M-DC8 + cells, also known as “slanDCs”, has been described in blood and detected even in inflamed secondary lymphoid organs and non-lymphoid tissues. Nevertheless, hallmarks of slan/M-DC8 + cells in tissues are poorly defined. Herein, we report a detailed characterization of the phenotype and function of slan/M-DC8 + cells present in human tonsils. We found that tonsil slan/M-DC8 + cells represent a unique DC cell population, distinct from their circulating counterpart and also from all other tonsil DC and monocyte/macrophage subsets. Phenotypically, slan/M-DC8 + cells in tonsils display a CD11c + HLA-DR + CD14 + CD11b dim/neg CD16 dim/neg CX3CR1 dim/neg marker repertoire, while functionally they exhibit an efficient antigen presentation capacity and a constitutive secretion of TNFα. Notably, such DC phenotype and functions are substantially reproduced by culturing blood slan/M-DC8 + cells in tonsil-derived conditioned medium (TDCM), further supporting the hypothesis of a full DC-like differentiation program occurring within the tonsil microenvironment. Taken together, our data suggest that blood slan/M-DC8 + cells are immediate precursors of a previously unrecognizedcompetent DC subset in tonsils, and pave the way for further characterization of slan/M-DC8 + cells in other tissues.