ABSTRACT
BACKGROUND: Recent findings have shown that the surface expression of the high-affinity receptor for IgE (FcepsilonRI) on human CD1a(+) Langerhans cells (LC) and related dendritic cells (DC) in the skin, despite a constant intracellular expression of its alpha chain (FcepsilonRIalpha), is highly up-regulated in atopic dermatitis. Moreover, this surface expression correlates with the IgE serum level, strongly suggesting yet-to-be-defined common signals in the regulation of FcepsilonRI display on LC/DC and IgE synthesis. OBJECTIVES: In this study we examined the influence of different cytokines on the expression of FcepsilonRI on in vitro-generated CD1a(+) LC/DC. METHODS: CD34(+) precursor cells were isolated from cord blood with use of high-gradient magnetic cell sorting, cultured with GM-CSF, TNF-alpha, IL-4, or IFN-gamma, and surface and cytoplasmic staining for flow cytometry were performed. RESULTS: IL-4 strongly enhanced the generation of CD1a(+) LC/DC and also up-regulated the expression of the skin-homing structures E-cadherin and cutaneous lymphocyte antigen. In contrast, IFN-gamma was found to suppress the E-cadherin expression and to be a strong antagonist of IL-4 by inhibiting the production of CD1a(+) cells. Most important, IL-4 induced the cytoplasmic expression of FcepsilonRIalpha in CD1a(+) LC/DC but not its surface expression. This up-regulation was antagonized by IFN-gamma. CONCLUSION: IL-4 is not only a key cytokine in the regulation of IgE but also induces the expression of its receptor binding chain as well as up-regulation of skin homing molecules on LC/DC. Expression of these structures during generation of LC/DC reflects the in vivo situation encountered in LC.
Subject(s)
Dendritic Cells/metabolism , Interleukin-4/pharmacology , Intracellular Membranes/metabolism , Receptors, IgE/metabolism , Antigens, CD1/analysis , Cells, Cultured , Dendritic Cells/drug effects , Dendritic Cells/immunology , Humans , Immunoglobulin epsilon-Chains/metabolism , Interferon-gamma/pharmacology , Protein Isoforms/analysis , Protein Isoforms/metabolism , RNA, Messenger/metabolism , Receptors, Fc/genetics , Receptors, Fc/metabolismSubject(s)
Dendritic Cells/immunology , Interleukin-4/pharmacology , Receptors, IgE/biosynthesis , Receptors, IgE/genetics , Antigens, CD1/metabolism , Antigens, CD34/metabolism , Fetal Blood/cytology , Fetal Blood/immunology , Humans , In Vitro Techniques , Infant, Newborn , Phenotype , RNA, Messenger/geneticsABSTRACT
In the present study, we investigated the in vitro migratory activity of human epidermal Langerhans cells (LC). Freshly isolated LC exhibit very low spontaneous migration. In contrast, a strong migration is recorded 6 h after the isolation. This migration is due to the presence of GM-CSF released by surrounding keratinocytes in vitro. Picomolar concentrations of GM-CSF promote the migration of LC, but nanomolar concentrations are inhibitory. Checker-board experiments indicate that GM-CSF acts as a chemokinetic mediator for LC, Bulk cultured LC exhibit a significant decrease of their spontaneous migration but retain the capacity to respond to GM-CSF only at nanomolar concentrations. In contrast, LC cultured in the presence of picomolar concentrations of exogenous GM-CSF exhibit a spontaneous migratory activity comparable to that of 6 h rested LC but do not respond to GM-CSF. These results suggest that GM-CSF represents an essential factor triggering the egress of LC from their epidermal environment.
