Document 0164
 DOCN  M9550164
 TI    [Cutaneous immune system]
 DT    9505
 AU    Schmitt D; INSERM Unite 346, Clinique Dermatologique, Hopital;
       Edouard-Herriot, Lyon, France.
 SO    C R Seances Soc Biol Fil. 1994;188(3):207-21. Unique Identifier :
       AIDSLINE MED/95136104
 AB    The skin is not only a physico-mechanical barrier between the
       environment and the body, but it also functions as an immune organ. The
       immunological function of epidermis is principally linked to the
       presence in this tissue of a distinct subpopulation of dendritic cells:
       the Langerhans cells (LC). LC constitute 2-4% of epidermal cell
       population and within epidermis they are the only cells which express
       MHC class II antigens constitutively. LC play a key role in the
       initiation of T cell responses to cutaneous antigens by picking up the
       antigen and migrating to the draining lymph node where they trigger
       specific T cell activation. There is also evidence that keratinocytes
       participate in immune responses in the skin since these cells produce a
       wide variety of cytokines that can modulate T cell responses. Dendritic
       cells comprise a system of highly efficient antigen-presenting cells
       which initiate immune responses such as the sensitization of T cells
       restricted by major histocompatibility complex molecules, the rejection
       of organ transplants and the formation of T-cell-dependent antibodies.
       Dendritic cells are found in many non-lymphoid tissues, such as skin and
       mucosa (Langerhans cells), and they migrate after antigen capture
       through the afferent lymph or the bloodstream to lymphoid organs, where
       they efficiently present antigen to T cells. Dendritic cells are
       difficult to isolate and, although they originate from bone marrow their
       growth and differentiation are still poorly characterized. Granulocyte
       macrophage-colony stimulating factor (GM-CSF) favours the out-growth of
       dendritic cells from mouse peripheral blood. The cooperation between
       GM-CSF and tumour necrosis factor-alpha (TNF-alpha) is crucial for the
       generation of human dendritic/Langerhans cells from CD34+ haematopoietic
       progenitors. The availability of large numbers of these cells should now
       facilitate the understanding of their role in immunological regulation
       and disorder. Recent studies reported that after 2-3 days in vitro
       incubation, both murine and human LC undergo profound phenotypic
       changes, as an enhancement in the expression of MHC class I and II
       antigens, LFA-3 and ICAM-1 molecules, a concomitant decrease of CD1a
       antigens and a loss of Fc gamma RII. Furthermore, cultured LC (cLC) lose
       or markedly reduce their specific cytoplasmic organelles: the Birbeck
       granules. Therefore, after a 2-3 days in vitro incubation, LC seem to
       acquire most of the features of lymphoid dendritic cells.(ABSTRACT
       TRUNCATED AT 400 WORDS)
 DE    Animal  Cytokines/IMMUNOLOGY  CD4-Positive T-Lymphocytes/IMMUNOLOGY
       CD8-Positive T-Lymphocytes/IMMUNOLOGY  Dermatitis, Allergic
       Contact/IMMUNOLOGY  Dermatitis, Atopic/IMMUNOLOGY  English Abstract
       Human  HLA-D Antigens/IMMUNOLOGY  *Immune System  In Vitro
       Keratinocytes/IMMUNOLOGY  Langerhans Cells/IMMUNOLOGY
       Skin/CHEMISTRY/CYTOLOGY/*IMMUNOLOGY  T-Lymphocyte Subsets/IMMUNOLOGY
       JOURNAL ARTICLE  REVIEW  REVIEW, TUTORIAL

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