Human Monocytes - CD14, CD16 - Ziegler-Heitbrock

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Scanning EM of human blood monocytes
(Picture provided by David Hockley, NIBSC, Potters Bar, UK)

Human Monocytes
in Health and Disease

Monocytes develop in the bone marrow from myelo-monocytic stem cells via a common monocyte progenitor (cMoP) and then a pre-monocyte.  From bone marrow monocytes go into blood, where they circulate for a few days in order to then migrate into tissues. Cells of this lineage in blood are termed monocytes, once they are in tissue they are called macrophages. In the tissue they immediately start to mature into macrophages. Tissue macrophages are extremely heterogenous dependent on the type of tissue (microglial cells in the brain, alveolar macrophages in the lung, osteoclasts in bone) and on the process (giant cells in granuloma, tumor associated macrophages in malignancy). 

In the past monocytes have been studied based on morphology under the microscope or they have been identified based on biophysical properties in hematology cell counters. With the advent of flow cytometry and with the use of monoclonal antibodies a more precise definition of these cells became available. This entailed the discovery of monocyte subsets with different phenotype and function and with diagnostic and prognostic implications. At this point we define classical CD14++CD16- monocytes, non-classical CD14+CD16++ monocytes and intermediate CD14++CD16+ monocytes.

While CD14 and CD16 markers have been used to categorize tissue resident macrophages and in-vitro generated macrophages, the literature compiled herein is restricted to native cells in blood from healthy donors and patients without or with treatment.

Recently mass cytometry and single cell sequencing have begun to expand and refine the definition of subsets of monocytes and this will shape our understanding of these cells in the future. 

This page provides protocols and literature regarding monocyte subsets and their precursors in humans and in non-human primates.

Monocytes and macrophages play important roles in the immune defence, inflammation and tissue remodelling and they do so by phagocytosis, antigen processing and presentation and by cytokine production.

Analysis of these processes can be done with primary cells or with model cell lines. Here the cell line Mono Mac 6 is a useful tool, which represents the only mature human monocytic cell line available to date. A little less mature is the companion cell line Mono Mac 1, which has been useful for studies on chemokine function. Protocols and literature for both cell lines can be found under this page.

The site is maintained by Loems Ziegler-Heitbrock and is up-dated regularly to include new protocols and publications.