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The M-DC8-positive leukocytes are a subpopulation of the CD14+ CD16+ monocytes
M Siedlar1, M Frankenberger, L H Ziegler-Heitbrock
1Institute of Immunology, University of München, Germany.
Abstract:
Recently, a population of M-DC8-positive leukocytes has been described as a new subpopulation of human dendritic cells (DC). In view of the expression of the CD16 antigen on these cells, as well as the finding that DC can arise from blood monocytes, we hypothesized that the expression of M-DC8 is mainly associated with the CD14+ CD16+ phenotype of blood monocytes. Immunofluorescence analysis of whole blood showed that the percentage of M-DC8+ cells is about three times lower than the percentage of CD14+ CD16+ monocytes among all leukocytes (0.32% versus 1.10%). Further, in addition to the expression of CD16, these M-DC8+ cells were also positive for CD14 at low density. Multicolor flow cytometric analysis of whole blood revealed that more than one third of the CD14+ CD16+ monocyte population expressed the M-DC8 antigen (42.3%), and almost all M-DC8+ cells were CD14-CD16-double-positive (87.5%). Finally, the M-DC8 antigen was also expressed on alveolar macrophages from healthy individuals, i.e., cells that are phenotypically and functionally related to the CD14+ CD16+ monocytes. Taken together, the data presented here clearly demonstrate that the M-DC8+ leukocytes are a subpopulation of the CD14+ CD16+ monocytes and may represent DC
Insights
M-DC8-positive leukocytes are identified as a subpopulation of CD14+ CD16+ monocytes, not a new type of dendritic cell (DC). These cells share characteristics with CD14+ CD16+ monocytes and alveolar macrophages.
Area of Science:
- Immunology
- Cell Biology
Background:
- A novel M-DC8-positive leukocyte population was recently described as a potential new subset of human dendritic cells (DC).
- Dendritic cells are known to originate from blood monocytes, which express CD14 and CD16 antigens.
Purpose of the Study:
- To investigate the hypothesis that M-DC8 expression is associated with the CD14+ CD16+ phenotype in blood monocytes.
- To characterize the M-DC8+ leukocyte population and its relationship to monocytes and dendritic cells.
Main Methods:
- Immunofluorescence analysis of whole blood to detect M-DC8 and CD14/CD16 expression.
- Multicolor flow cytometry to quantify M-DC8 antigen expression on CD14+ CD16+ monocytes.
- Analysis of M-DC8 expression on alveolar macrophages.
Main Results:
- M-DC8+ cells constituted a significantly smaller percentage of leukocytes (0.32%) compared to CD14+ CD16+ monocytes (1.10%).
- M-DC8+ cells expressed CD14 at low density and CD16.
- Over one-third (42.3%) of CD14+ CD16+ monocytes expressed M-DC8, and 87.5% of M-DC8+ cells were CD14+ CD16+.
- M-DC8 was also found on alveolar macrophages, which are related to CD14+ CD16+ monocytes.
Conclusions:
- M-DC8+ leukocytes represent a subpopulation of CD14+ CD16+ monocytes.
- The M-DC8+ population may not be a distinct dendritic cell subset but rather a monocyte-derived population.
- These findings clarify the identity of M-DC8+ leukocytes within the monocyte lineage.