CD1c-Expression by Monocytes – Implications for the Use of Commercial CD1c+ Dendritic Cell Isolation Kits

Abstract

Conventional dendritic cells (cDCs) comprise a heterogeneous population of cells that are important regulators of immunity and homeostasis. CD1c+ cDCs are present in human blood and tissues, and found to efficiently activate naïve CD4+ T cells. While CD1c is thought to specifically identify this subset of human cDCs, we show here that also classical and intermediate monocytes express CD1c. Accordingly, the commercial CD1c (BDCA-1)+ Dendritic Cell Isolation Kit isolates two distinct cell populations from blood: CD1c+CD14− cDCs and CD1c+CD14+ monocytes. CD1c+ cDCs and CD1c+ monocytes exhibited strikingly different properties, including their differential regulation of surface marker expression, their levels of cytokine production, and their ability to stimulate naïve CD4+ T cells. These results demonstrate that a commercial CD1c (BDCA-1)+ Dendritic Cell Isolation Kit isolates two functionally different cell populations, which has important implications for the interpretation of previously generated data using this kit to characterize CD1c+ cDCs.

Human Intestinal Mononuclear Phagocytes in Health and Inflammatory Bowel Disease

“…As previously shown by Jahnsen's group (75,168,234), Bernardo et al confirmed that immature Mfs are characterized as CD11c + Mfs and expressed monocyte-associated markers such as CCR2 and CX3CR1, while mature Mfs are characterized as CD11c − Mfs (225) (Figure 6). However, they did not find a difference of CD206 and CD163 expression between Mf populations (225), which are markers typically associated with mature Mfs (75,221) (Figure 6).…”

“…However, these CD14 + CD1c + monocytederived cells also expressed markers found on Mfs, including CD64 (166,167). In addition, Schrøder et al have recently shown that a fraction of CD14 + monocytes already expressed CD1c in blood (168). These CD14 + CD1c + cells characterized by Schrøder et al possess hallmarks of monocytes such as CCR2 expression, TNF induction after LPS treatment and lower efficiency to promote naïve T cell proliferation compared to blood CD14 − CD1c + cDCs (168).…”

“…In addition, Schrøder et al have recently shown that a fraction of CD14 + monocytes already expressed CD1c in blood (168). These CD14 + CD1c + cells characterized by Schrøder et al possess hallmarks of monocytes such as CCR2 expression, TNF induction after LPS treatment and lower efficiency to promote naïve T cell proliferation compared to blood CD14 − CD1c + cDCs (168). Together, these data support that tissue CD14 + CD1c + monocyte-derived cells could represent a highly plastic Mf subset, which shared some capacities with cDCs, rather being than a bona fide cDC subset (130,169).…”

Human dendritic cell subsets: an update

“…Detailed phenotyping and single‐cell gene expression studies have recently characterized two subsets of cDC2 in human blood, one ‘DC‐like’ with higher expression of CD5, CD1c, HLA‐DQ and IRF4 and the other more ‘monocyte‐like’ showing CD14, CD32, CD36, CD163 and proportionately higher MAFB expression . CD14 + CD1c + cells have previously been detected and characterized as CD1c + monocytes but by gene expression, most cluster with cDC2 . In tissues, especially during inflammation, and in humans affected by cancer, it is relatively easy to detect dual positive CD1c + CD14 + cells but the origin of these may be difficult to ascertain precisely because as mo‐DC, they converge towards the monocyte‐like cDC2 phenotype .…”

Myeloid Cells Enriched for a Dendritic Cell Population From People Living With HIV Have Altered Gene Expression Not Restored by Antiretroviral Therapy

“…It is known that using bead enrichment alone yields DC preparations that are contaminated with other cell types (48), and for this reason, we used a subsequent FACS purification step. The magnetic bead enriched mDCs or monocyte populations were further purified by fluorescence-activated cell sorting (FACS; Becton Dickinson, FACSARIA).…”