title: Characterization of Antigen-Presenting Macrophages and Dendritic Cells in the Healthy Human Sclera.
abstract: OBJECTIVE
  The sclera is mainly made of collagen and fibroblasts. The aim of this study was to analyze whether immune cells are present in the healthy human sclera.
  
  
  METHODS
  Ten human anterior episcleral or stromal tissue samples from globe donors were immunohistochemically examined using confocal microscopy. The expression of the macrophage markers CD68, CD163 and CD11b, CD45 (a general leukocyte marker), MHCII (expressed by antigen-presenting cells [APCs]), CD11c (dendritic cell marker), lymphatic endothelium hyaluronan receptor-1 (LYVE1; expressed on lymphatic endothelium and macrophage subsets), chemokine receptor 7 (CCR7, a homing receptor for leukocytes), CXCL12 (expressed by activated leukocytes), CCR2 (a marker for inflammatory monocytes), and glial fibrillary acidic protein (GFAP; expressed by astrocytes) was analyzed and quantified.
  
  
  RESULTS
  In the episclera, a high number of cells (≥40 cells/mm2) were immunoreactive for CD68, CD45, MHCII, CCR7, LYVE1, and CD11b. Lower numbers (<20 cells/mm2) were positive for CXCL12, CCR2, and GFAP. The episclera showed a significantly higher number of cells compared to the stroma (P = 0.008). MHCII+ cells could be double positive for CCR7, CD45, CD11c, or CD11b and seldom CXCL12. Macrophages were most likely from the M1 type (CD68+, CD163-).
  
  
  CONCLUSIONS
  The healthy human sclera contains several macrophage populations, which can function as APCs, with the highest density being present in the episclera. Most cells express macrophage markers and may function as APCs. The presence of these cells might indicate that scleral immune cells are important for maintaining physiological functions in the eye and may potentially contribute to blood vessel homeostasis.
authors.affiliation: Department of Ophthalmology University of Cologne, Cologne, Germany.
authors.forename: Simona L
authors.initials: SL
authors.lastname: Schlereth
authors.affiliation: Department of Ophthalmology University of Cologne, Cologne, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Kremers
authors.affiliation: Department of Ophthalmology, Research Program for Experimental Ophthalmology and Glaucoma Research, Paracelsus Medical University, Salzburg, Austria 3Department of Anatomy, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Falk
authors.initials: F
authors.lastname: Schrödl
authors.affiliation: Department of Ophthalmology University of Cologne, Cologne, Germany.
authors.forename: Claus
authors.initials: C
authors.lastname: Cursiefen
authors.affiliation: Department of Ophthalmology University of Cologne, Cologne, Germany.
authors.forename: Ludwig M
authors.initials: LM
authors.lastname: Heindl