A novel role for Notch ligand Delta-1 as a regulator of human Langerhans cell development from blood monocytes

Abstract

Human Langerhans cells (LCs) are of hematopoietic origin, but cytokine regulation of their development is not fully understood. Notch ligand Delta-1 is expressed in a proportion of the skin. Granulocyte-macrophage colony-stimulating factor (GM-CSF) and transforming growth factor-beta1 (TGF-beta1) are also secreted in the skin. We report here that Delta-1, in concert with GM-CSF and TGF-beta1, induces the differentiation of human CD14(+) blood monocytes into cells that express LC markers: CD1a, Langerin, cutaneous lymphocyte-associated antigen, CC chemokine receptor 6, E-cadherin, and Birbeck granules. The resulting cells display phagocytic activity and chemotaxis to macrophage inflammatory protein-1alpha (MIP-1alpha). In response to CD40 ligand and tumor necrosis factor alpha, the cells acquire a mature phenotype of dendritic cells that is characterized by up-regulation of human leukocyte antigen (HLA)-ABC, HLA-DR, CD80, CD86, CD40, and CD54 and appearance of CD83. These cells in turn show chemotaxis toward MIP-1beta and elicit activation of CD8(+) T cells and T helper cell type 1 polarization of CD4(+) T cells. Thus, blood monocytes can give rise to LCs upon exposure to the skin cytokine environment consisting of Delta-1, GM-CSF, and TGF-beta1, which may be, in part, relevant to the development of human epidermal LCs. Our results extend the functional scope of Notch ligand delta-1 in human hematopoiesis.

Functional Langerinhigh-Expressing Langerhans-like Cells Can Arise from CD14highCD16− Human Blood Monocytes in Serum-Free Condition

“…First, both cell types increased their pool of polymerized actin upon fMLF stimulation, suggesting that they were both responsive to chemokine stimulation. We then demonstrated that immature MDLCs and MDDCs responded to MIP-3b/CCL20 and not to MIP-3a/CCL19, in line with other studies (28). Both cell types also responded to MCP-1/CCL2 in accordance with their respective CCR2 expression levels.…”

“…We assumed that other serum lipids such as high-density lipoproteins might be able to act similarly. Thus, serum lipids appeared to be responsible for a marked alteration of LC differentiation of monocytes in previous studies (28,31,32).…”

“…5B). Hoshino et al (28) reported that the culture of GM-CSF/TGF-b1 MDLCs with immobilized recombinant Notch d ligand 1 or DLL1 promoted E-cadherin expression (28).…”

“…A careful analysis of these protocols revealed that only Hoshino et al (28) reported simple and reproducible culture conditions leading to MDLCs displaying bona fide LC features. However, the lack of comparison with freshly isolated cells did not allow us to consider it as the most convincing way the differentiate monocytes into MDLCs.…”

“…To investigate the mechanisms driving the differentiation of monocytes toward DC subsets, a plethora of in vitro studies have been reported during the past 2 decades, first starting from CD34 + hematopoietic stem cells (23)(24)(25) but also from monocytes as precursors of LC-like cells or monocyte-derived LCs (MDLCs) using various culture conditions (26)(27)(28)(29). A careful analysis of these protocols revealed that only Hoshino et al (28) reported simple and reproducible culture conditions leading to MDLCs displaying bona fide LC features.…”