Dendritic Cells as the Terminal Stage of Monocyte Differentiation

Abstract

Monocytes (MO) cultured for ≥5 days with either macrophage-CSF (M-CSF) or granulocyte macrophage (GM)-CSF and IL-4 differentiated without concomitant proliferation into CD14+ macrophages (Mφ) or CD1a+ dendritic cells (DC), respectively. When adherent and nonadherent CD14high Mφ from M-CSF cultures were separated and cultured further in cytokine-free medium or with GM-CSF/IL-4, most cells from both fractions that were exposed to GM-CSF/IL-4 acquired CD1a expression and DC morphology and function. Conversely, GM-CSF/IL-4 withdrawal at day 5 and additional culture of sorted CD1a+ DC for 2 to 7 days in cytokine-free medium led to cells rapidly becoming adherent CD1a−CD14+ Mφ. Replacing GM-CSF/IL-4 with M-CSF hastened the conversion of DC to Mφ without increasing cell numbers. CD1a+CD14−CD83+ mature DC were induced by a ≥2-day exposure to MO-conditioned medium, LPS, or TNF-α/IL-1β. Upon cytokine removal or culture with M-CSF, DC that had been pushed to maturation by conditioned medium or LPS remained stable or died in the new environment. TNF-α/IL-1β-driven DC displayed heterogeneous CD83 expression and could thus be sorted into CD83high and CD83low/− cells; in cytokine-free medium or in M-CSF, most CD83low/− cells converted to Mφ, whereas most CD83high cells remained nonadherent CD1a+CD14− or died and thus appeared truly terminally differentiated. Hence, MO are precursors of Mφ as well as of DC, with each cell type having the capability to convert into the other until late in the differentiation/maturation process. Accordingly, the cytokine environment and the presence of differentiation and/or other stimulatory signals may be the “final decision-making factors” determining whether these cells will acquire DC or Mφ characteristics and function.

Differentiation and function of human monocyte-derived dendritic cells under the influence of leflunomide

“…Phenotypic analysis showed that 80-90% of immature MDDC expressed HLA-DR, CD40, CD54 and CD86, 47% were CD80 positive, while only a small subset was CD83+. The obtained results are in agreement with the data showing that DC de novo express CD80 and upregulate the expression of CD40, HLA-DR, CD4, CD11b, CD11c (Pickl et al, 1996;Palucka et al, 1998). The continuous presence of leflunomide during the differentiation of MDDC was followed by a significantly inhibited density of co-stimulatory and adhesive molecules on the cell surface (CD40, CD54 and C86), and a reduced percentage of cell expression of CD80.…”

Tacrolimus and Cyclosporine a Inhibit Allostimulatory Capacity and Cytokine Production of Human Myeloid Dendritic Cells

“…The typical microscopic appearance of DCs, including the formation of dendrites and veiled cell morphology, was seen in DCs generated in the presence of GM-CSF plus IL-4. 1 CsA or tacrolimus treatment resulted in no change in DC appearance compared with control DCs (Figure 1). Monocytes cultured in the absence of IL-4 or GM-GSF for the same length of time maintained their typical rounded shape (Figure 1).…”

“…Myeloid dendritic cells (DCs) are important monocyte-derived, antigen-presenting cells that initiate and modulate immune responses. 1,2 They capture and process antigens and transport them from peripheral tissues to secondary lymphoid organs, where they activate CD4 + and CD8 + T lymphocytes. 3,4 Antigen presentation by DCs to T cells occurs in the context of cell-surface major histocompatibility complex (MHC) class II molecules and costimulatory/accessory signals, in particular CD40, CD80, and CD86 surface molecules.…”

The Monocytic Cell Line THP-1 as a Validated and Robust Surrogate Model for Human Dendritic Cells

“…Hence, there was an urgent need for alternative robust human-derived models. In this context, various protocols generating dendritic cell surrogates derived from human donor-derived peripheral blood monocytes (PBMCs) to study skin sensitization and inflammation have been reported [ 47 , 48 , 49 , 50 ]. However, the isolation and differentiation of PBMCs comes with various technical and biological limitations, such as the amount, availability, and donor heterogeneity [ 51 , 52 ].…”