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Published on: November 4, 2016
Flow Cytometric Challenges in Plasmacytoid Dendritic Cell (pDC) Identification: Limitation of BDCA-4 (CD304)-Based
Sarolta Demeter1,2, Tünde Fekete1, Beáta Scholtz3
1Department of Immunology, Faculty of Medicine, University of Debrecen, H-4032 Debrecen, Hungary.
Insights
Accurate identification of plasmacytoid dendritic cells (pDCs) is crucial for understanding diseases. This study developed a new gating strategy to reliably identify pDCs even when BDCA-4 markers are expressed on other cells.
Area of Science:
- Immunology
- Cell Biology
Background:
- Plasmacytoid dendritic cells (pDCs) are key players in type I interferon production and disease pathogenesis.
- Identifying pDCs in peripheral blood mononuclear cells (PBMCs) is challenging due to variable surface marker expression (BDCA-2, BDCA-4).
- BDCA-4 expression can increase on non-pDC subsets, like monocytes, after prolonged stimulation, complicating pDC identification.
Purpose of the Study:
- To investigate BDCA-4 expression dynamics on pDCs and other PBMCs after Toll-like receptor (TLR) 7 and TLR9 agonist stimulation.
- To develop and validate a reliable gating strategy for accurate pDC identification in complex cellular environments.
Main Methods:
- Flow cytometry analysis of PBMCs from healthy individuals.
- Prolonged stimulation with TLR7 and TLR9 agonists.
- Development of a novel gating strategy combining BDCA-4 positivity with non-pDC markers.
Main Results:
- Prolonged stimulation significantly increased BDCA-4 expression on CD14+ monocytes and other non-pDC populations.
- The developed gating strategy effectively excluded non-pDCs, enabling accurate pDC identification.
- This method allows reliable pDC detection using two fluorescent channels under various conditions, including inflammation.
Conclusions:
- BDCA-4 is not a perfectly specific marker for pDCs during prolonged immune activation.
- A refined gating strategy is essential for accurate pDC identification in heterogeneous cell populations.
- This approach enhances the reliability of pDC analysis in both healthy and pathological states.
Abstract:
Plasmacytoid dendritic cells (pDCs) are a unique subset of dendritic cells specialized in rapid and robust type I interferon (IFN) production, playing critical roles in the pathogenesis and pathomechanisms of many human diseases. Accurate identification of pDCs in peripheral blood mononuclear cells (PBMCs) is challenging due to dynamic and non-exclusive specific expression of surface markers such as blood dendritic cell antigen (BDCA)-2 and BDCA-4. Although BDCA-4 is generally more stably expressed than BDCA-2, prolonged stimulation or inflammatory conditions can induce its expression on multiple non-pDC cell types, reducing the accuracy of pDC identification. Here, we thoroughly investigated BDCA-4 expression dynamics on pDCs and other PBMC subsets following prolonged activation with Toll-like receptor (TLR) 7 and TLR9 agonists. Our flow cytometry analysis revealed a significant increase in BDCA-4-positive non-pDC populations after extended stimulation, primarily corresponding to CD14+ monocytes. To overcome this limitation, we performed a gating strategy combining BDCA-4 positivity with a cocktail of non-pDC markers, enabling the exclusion of non-pDCs and accurate identification of pDCs. This approach enables the reliable identification of pDCs within heterogeneous cell populations using only two fluorescent channels in healthy conditions and even during strong activation or pathological states characterized by chronic inflammation.
