title: Age-related changes in expression and function of Toll-like receptors in human skin.
abstract: Toll-like receptors (TLRs) initiate innate immune responses and direct subsequent adaptive immunity. They play a major role in cutaneous host defense against micro-organisms and in the pathophysiology of several inflammatory skin diseases. To understand the role of TLRs in the acquisition of immunological competence, we conducted a comprehensive study to evaluate TLR expression and function in the developing human skin before and after birth and compared it with adults. We found that prenatal skin already expresses the same spectrum of TLRs as adult skin. Strikingly, many TLRs were significantly higher expressed in prenatal (TLRs 1-5) and infant and child (TLRs 1 and 3) skin than in adult skin. Surprisingly, neither dendritic cell precursors in prenatal skin nor epidermal Langerhans cells and dermal dendritic cells in adult skin expressed TLRs 3 and 6, whereas the staining pattern and intensity of both TLRs in fetal basal keratinocytes was almost comparable to those of adults. Stimulation of primary human keratinocytes from fetal, neonatal and adult donors with selected TLR agonists revealed that the synthetic TLR3 ligand poly (I:C) specifically, mimicking viral double-stranded RNA, induced a significantly enhanced secretion of CXCL8/IL8, CXCL10/IP-10 and TNFα in fetal and neonatal keratinocytes compared with adult keratinocytes. This study demonstrates quantitative age-specific modifications in TLR expression and innate skin immune reactivity in response to TLR activation. Thus, antiviral innate immunity already in prenatal skin may contribute to protect the developing human body from viral infections in utero in a scenario where the adaptive immune system is not yet fully functional.
authors.affiliation: Department of Dermatology, Division of Immunology, Allergy and Infectious Diseases, Laboratory of Cellular and Molecular Immunobiology of the Skin, Medical University of Vienna,  Austria.
authors.forename: Nousheen
authors.initials: N
authors.lastname: Iram
authors.forename: Michael
authors.initials: M
authors.lastname: Mildner
authors.forename: Marion
authors.initials: M
authors.lastname: Prior
authors.forename: Peter
authors.initials: P
authors.lastname: Petzelbauer
authors.forename: Christian
authors.initials: C
authors.lastname: Fiala
authors.forename: Stefan
authors.initials: S
authors.lastname: Hacker
authors.forename: Alice
authors.initials: A
authors.lastname: Schöppl
authors.forename: Erwin
authors.initials: E
authors.lastname: Tschachler
authors.forename: Adelheid
authors.initials: A
authors.lastname: Elbe-Bürger
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging; D002478:Cells, Cultured; D054357:Chemokine CXCL10 / Q000096:biosynthesis; D002648:Child; D016207:Cytokines / Q000096:biosynthesis; D003713:Dendritic Cells / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate; D007223:Infant; D016209:Interleukin-8 / Q000096:biosynthesis; D015603:Keratinocytes / Q000378:metabolism; D007801:Langerhans Cells / Q000378:metabolism; D008875:Middle Aged; D011070:Poly I-C / Q000276:immunology / Q000378:metabolism; D012867:Skin / Q000196:embryology / Q000254:growth & development* / Q000276:immunology* / Q000378:metabolism; D017193:Skin Diseases, Viral / Q000276:immunology*; D051193:Toll-Like Receptors / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D055815:Young Adult
chemical_list: C114753:CXCL10 protein, human; C508606:CXCL8 protein, human; D054357:Chemokine CXCL10; D016207:Cytokines; D016209:Interleukin-8; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D011070:Poly I-C