Primate Monocytes - CD14, CD16 - Ziegler-Heitbrock

Distribution of subsets of blood monocytic cells throughout life.

Abstract

Currently, it is well established that monocytes are a heterogeneous type of cell consisting of phenotypically and functionally distinct subpopulations found to be numerically altered in blood in patients with a wide variety of disease conditions, such as infection, autoimmunity, respiratory and cardiovascular diseases, and inflammatory disorders.1,2 Thus, 3 subpopulations of circulating monocytic cells have been identified based on expression of the CD14 LPS receptor and the CD16 low-affinity Fc IgG receptor: (1) CD14hiCD162 classical monocytes (cMos), (2) CD14hiCD161 intermediate monocytes (iMos), and (3) CD142/lo CD161 nonclassical monocytes (ncMos).3 Monocytes circulate in blood for up to 3 days until recruited to virtually any human tissue, where they differentiate into either tissue macrophages or myeloid dendritic cells.4 Then, tissue macrophages can migrate from their tissue location through the lymph system5 before they potentially die outside the circulation.6 Despite our knowledge of the biology of monocytes increasing in recent years, normal reference ranges for the distinct monocyte subsets in blood throughout life (eg, from cord blood [CB] and newborns to elderly subjects) have never been systematically defined. Moreover, the precise maturational and functional relationship between the distinct populations of blood monocytes and their tissue distribution profiles remains unknown.