Distinguishing human peripheral blood CD16 myeloid cells based on phenotypic characteristics.

Myeloid lineage cells present in human peripheral blood include dendritic cells (DC) and monocytes. The DC are identified phenotypically as HLA-DR cells that lack major cell surface lineage markers for T cells (CD3), B cells (CD19, CD20), NK cells (CD56), red blood cells (CD235a), hematopoietic stem cells (CD34), and Mo that express CD14. Both DC and Mo can be phenotypically divided into subsets. DC are divided into plasmacytoid DC, which are CD11c , CD304 , CD85g , and myeloid DC that are CD11c . The CD11c DC are readily classified as CD1c DC and CD141 DC. Monocytes are broadly divided into the CD14 CD16 (classical) and CD14 CD16 subsets (nonclassical). A population of myeloid-derived cells that have DC characteristics, that is, HLA-DR and lacking lineage markers including CD14, but express CD16 are generally clustered with CD14 CD16 monocytes. We used high-dimensional clustering analyses of fluorescence and mass cytometry data, to delineate CD14 monocytes, CD14 CD16 monocytes (CD16 Mo), and CD14 CD16 DC (CD16 DC). We sought to identify the functional and kinetic relationship of CD16 DC to CD16 Mo. We demonstrate that differentiation of CD16 DC and CD16 Mo during activation with IFNγ in vitro and as a result of an allo-hematopoietic cell transplant (HCT) in vivo resulted in distinct populations. Recovery of blood CD16 DC in both auto- and allo-(HCT) patients after myeloablative conditioning showed similar reconstitution and activation kinetics to CD16 Mo. Finally, we show that expression of the cell surface markers CD300c, CCR5, and CLEC5a can distinguish the cell populations phenotypically paving the way for functional differentiation as new reagents become available.