Antagonistic effects of IL‐4 and TGF‐β1 on Langerhans cell‐related antigen expression by human monocytes

Abstract

In this study, we analyzed the specific effects of transforming growth factor β (TGF-β1) and/or IL-4 on monocyte-derived cells. Monocytes were cultured with GM-CSF, GM-CSF/TGF-β1, GM-CSF/IL-4, or GM-CSF/IL-4/TGF-β1 before cell morphology, phenotype, and function were assessed. As expected, interleukin-4 is mandatory for monocyte differentiation into potent allostimulatory DC. In its absence, monocyte-derived cells share many phenotypic and functional features with macrophages. However, it is interesting that the cells express E-cadherin, independent of exogenous TGF-β1, and addition of the cytokine induced CCR6 expression. Most importantly, a subset of monocytes cultured with GM-CSF/TGF-β1 expresses Langerin, as confirmed by electron microscopy analysis. Langerin engagement with specific monoclonal antibodies induces its internalization and the formation of typical Birbeck granules. Monocytes cultured in GM-CSF/IL-4 did not express the LC markers E-cadherin, CCR6, or Langerin. The simultaneous addition of TGF-β1 allows most of the cells to express E-cadherin but rarely CCR6 and Langerin. Taken together, the results add further evidence that LC can derive from monocytes and demonstrate an antagonistic effect of IL-4 and TGF-β1 on monocyte differentiation toward the LC pathway.