While DC2 readily achieve it under TGF-β1/GM-CSF alone conditions (13), Notch signaling, which is detected in LCH lesions (22), is an additional requirement for Langerin expression by monocytes (13, 20, 37, 38) and was recently implicated in the differentiation of normal epidermal LC (42). Here, CSF2 is linked to Langerhans cell histiocytosis.