title: Differential extracellular signaling via Fc gamma R and FMLP in functionally distinct antigen-presenting cell subsets: ultraviolet-induced epidermal macrophages versus Langerhans cells.
abstract: Sunburned skin is characterized by expanded numbers of macrophages (ultraviolet [UV]-MPH), and these UV-MPH differ from Langerhans cells (LC) in their abilities to initiate T-cell-mediated immune reactions. UV-MPH and LC may themselves be differentially responsive to the surrounding milieu, which may in turn modulate their immunoregulatory activity. We asked whether immunologic signal responsiveness, as assessed by cytosolic calcium mobilization, differed among normal human LC, UV-MPH, and normal blood monocytes. LC from normal skin and UV-MPH from UV-exposed skin were distinguished from keratinocytes in epidermal cell suspensions by labeling with anti-HLA-DR. Intracellular calcium content was monitored in real time with the calcium indicator, indo-1, after cross-linking Fc gamma RI, Fc gamma RII, CD11b, CD11c, or CD18 molecules, or addition of interleukin-1 alpha, IL-1 beta, interferon-gamma, bradykinin, substance P, or FMLP. Using flow cytometric analysis of cell suspensions, UV-MPH and blood monocytes were triggered by cross-linking Fc gamma RII (flux of 6.05 and 12.2, respectively). UV-MPH could also be triggered by Fc gamma RI crosslinking and FMLP (flux of 6.41 and 15.54, respectively). By contrast, none of these inflammatory stimuli could cause cytosolic calcium mobilization in normal LC (Flux of -0.2 by FcRII, and 0.18 by FMLP). Because LC calcium flux may be dependent upon extracellular attachments, LC were anchored onto fibronectin-coated coverslips and then their Fc gamma RII was crosslinked in a continuous flow chamber. However, image analysis also failed to detect calcium flux. Neither population responded to interleukin-1, interferon-gamma, bradykinin, substance P, or beta 2 integrin crosslinking. These results indicate that blood monocytes and infiltrating macrophages differ substantially from LC in their responses to immune complexes and chemoattractants. Differential responsiveness to the inflammatory milieu may influence the antigen presenting or effector capabilities of these populations.
authors.affiliation: Immunodermatology Unit, University of Michigan, Ann Arbor, USA.
authors.forename: A
authors.initials: A
authors.lastname: Shibaki
authors.forename: A
authors.initials: A
authors.lastname: Ohkawara
authors.forename: K D
authors.initials: KD
authors.lastname: Cooper
mesh_terms: D000938:Antigen-Presenting Cells / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000494:pharmacology; D000078404:Epidermal Cells; D004817:Epidermis / Q000528:radiation effects; D005110:Extracellular Space / Q000502:physiology*; D005353:Fibronectins / Q000378:metabolism; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D007801:Langerhans Cells / Q000502:physiology; D008264:Macrophages / Q000502:physiology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology*; D017452:Receptors, IgG / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D005353:Fibronectins; D005456:Fluorescent Dyes; D017452:Receptors, IgG; D009240:N-Formylmethionine Leucyl-Phenylalanine; D002118:Calcium; D016257:Fura-2