Original Research ARTICLE
A novel, five-marker alternative to CD16-CD14 gating to identify the three human monocyte subsets
- 1Singapore Immunology Network (A*STAR), Singapore
- 2School of Biological Sciences, College of Science, Nanyang Technological University, Singapore
- 3National Centre for Infectious Diseases (NCID), Singapore
- 4Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore
Human primary monocytes are heterogeneous in terms of phenotype and function, but are sub-divided only based on CD16 and CD14 expression. CD16 expression distinguishes a subset of monocytes with highly pro-inflammatory properties from non-CD16 expressing “classical” monocytes. CD14 expression further subdivides the CD16+ monocytes into non-classical CD14low and intermediate CD14high subsets. This long-standing CD16–CD14 classification system, however, has limitations as CD14 is expressed in a continuum, leading to subjectivity in delineating the non-classical and intermediate subsets; in addition, CD16 expression is unstable, making identification of the subsets impossible after in vitro culture or during inflammatory conditions in vivo. Hence, we aimed to identify the three monocyte subsets using an alternative combination of markers. Additionally, we wanted to address whether the monocyte subset perturbations observed during infection is real or an artefact of differential CD16 and/or CD14 regulation. Using cytometry by time-of-flight (CyTOF), we studied the simultaneous expression of 34 monocyte markers on total monocytes, and derived a combination of five markers (CD33, CD86, CD64, HLA-DR and CCR2), that could objectively delineate the three subsets. Using these markers, we could also distinguish CD16+ monocytes from CD16- monocytes after in vitro stimulation. Finally, we found that the observed expansion of intermediate (CD14high) monocytes in dengue virus-infected patients was due to up-regulated CD16 expression on classical monocytes. With our new combination of markers, we can now identify monocyte subsets without CD16 and CD14, and accurately re-examine monocyte subset perturbations in diseases.
Keywords: monocyte subsets, CD16, CD14, cytometry by time of flight, Dengue
Received: 06 Mar 2019;
Accepted: 11 Jul 2019.
Edited by:Anja Fuchs, Washington University in St. Louis, United States
Reviewed by:Heather Medbury, University of Sydney, Australia
Roberta Cappellari, University of Padova, Italy
Copyright: © 2019 Wong, Ong, Teng, Newell, Chen, Chen, Loy, Yeo and Fink. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Dr. Siew-Cheng Wong, Singapore Immunology Network (A*STAR), Singapore, 138648, Singapore, email@example.com