The novel subset of CD14⁺/CD16⁺ blood monocytes exhibits features of tissue macrophages

Abstract

The CD14+/CD16+ cells account for about 10% of all blood monocytes. They are characterized by a low level expression of the CD14 molecule and a high level expression of the CD16 (Fc gamma R III) molecule. Polymerase chain reaction analysis of mRNA prevalence in CD14+/CD16+ cells (compared to the regular CD14++ blood monocytes) demonstrates low levels of CD14 transcripts and high levels of CD16 transcripts, suggestive of a transcriptional control for both of these proteins. Analysis of additional cell surface molecules in three-color immunofluorescence reveals that CD14+/CD16+ cells express the Fc gamma R II in all, and Fc gamma R I and ICAM-1 in some donors. Furthermore, class II antigens are expressed at fourfold higher levels, while both, CD11b and CD33 cell surface proteins, are decreased by a factor of two. Transcript levels were reduced in CD14+/CD16+ cells for all three cell surface molecules. Since these phenotypic markers of the CD14+/CD16+ blood monocytes are reminiscent of tissue macrophages, we performed a comparative analysis with alveolar macrophages (AM). These cells are similar to the CD14+/CD16+ monocytes in that they show low levels of CD14 and strong expression of CD16. Furthermore, similar to the CD14+/CD16+ cells, the AM also exhibit higher levels of class II and lower levels of CD11b and CD33 when compared to the regular CD14++ blood monocytes. In vitro induction of maturation of blood monocytes by 5 day culture of peripheral blood mononuclear cells in 10% human serum will result in decreased CD14 and increased CD16 cell surface expression on the monocyte derived macrophages. At the same time, these cells acquire increased levels of class II and decreased levels of CD11b and CD33. Taken together, these data show that CD14+/CD16+ monocytes, while still in circulation, have acquired features in common with mature tissue macrophages.

Human MICL (CLEC12A) is differentially glycosylated and is down‐regulated following cellular activation

“…The down-regulation of FccRIII (CD16) has been observed on granulocytes that have been stimulated with fMLP [34], transmigrated across cultured epithelium [35] and on granulocytes undergoing apoptosis [36]. Recruited monocytes/MU also did not express CD16 in our model, corroborating the hypothesis that peripheral blood CD16 + monocytes are not recruited to inflammatory sites [19,37,38]. The upregulation of adhesion molecules, such as CD11b, has similarly been observed following both granulocyte and monocyte activation [39,40], and CD86 and MHC class II are recognized markers of monocyte/MU activation [41].…”

Pig Bone Marrow-Derived Macrophages Resemble Human Macrophages in Their Response to Bacterial Lipopolysaccharide

“…Human blood monocytes can be subdivided into subpopulations based upon the expression of CD14 and CD16 (40). We and others have shown that pig monocytes can also be separated into subpopulations that differ in their expression of CD16 and the scavenger receptor CD163 (21).…”

Functional characterization of peripheral blood dendritic cells and monocytes in systemic lupus erythematosus

“…monocyte-related subpopulation (CD14 -/low CD16 ? DC) initially described as a minor subset of mature monocytes [13][14][15]. Accordingly, this latter DC subpopulation seems to display intermediate features between a PB monocyte and DC, such as a high expression of FccRIII (CD16), a relatively low activity as APC in comparison with other peripheral blood DC and a high ability to generate in vitro activation of naive T cells.…”