Human monocyte heterogeneity--a nephrological perspective

Monocytes are key components of the innate immune system and are circulating precursors of tissue macrophages. Phenotypically and functionally, monocytes are a heterogeneous leukocyte subset. Based on the expression of CD14 and CD16, three human monocyte subsets can be distinguished: CD14++CD16-, CD14++CD16+ and CD14(+)CD16+ monocytes. The latter two subsets are often summarized as CD16+ monocytes. As these CD16+ cells are expanded in inflammatory conditions including end-stage renal disease, they have traditionally been termed proinflammatory monocytes, which is in contrast to murine monocyte nomenclature. More, each dialysis session induces a transient CD16+ monocytopenia.. In end-stage renal disease, both higher predialytic counts of CD16+ monocytes, and dialysis-induced CD16+ monocyte kinetic are predictors of cardiovascular outcome. So far, the functional differences of monocyte subsets and their pathophysiological role are still insufficiently understood.