title: Mast cells are present in the choroid of the normal eye in most vertebrate classes.
abstract: OBJECTIVE
  Mast cells are bone marrow-derived tissue-homing leukocytes, which have traditionally been regarded as effector cells in allergic disorders, responses against parasites, and regulation of blood flow, but a broader perspective of their functional heterogeneity, such as immunomodulation, angiogenesis, tissue repair, and remodeling after injury, is now emerging. The persistence of mast cells in connective tissues throughout the evolution of vertebrates is evidence of strong selective pressure suggesting that these cells must have multiple beneficial and important roles in normal homeostasis. While mast cells are present within the uveal tract of eutherian mammals, there is little known about their presence in the choroid of other vertebrate classes.
  
  
  METHODS
  Eye tissues from a range of vertebrate species (fish, amphibian, reptiles, birds, marsupials, monotreme, and eutherian mammals) were investigated. Tissues were fixed in either 2% glutaraldehyde, 2% paraformaldehyde or a mixture of both and processed for resin embedding. Semi-thin sections of the retina and choroid were cut and stained with toluidine blue.
  
  
  CONCLUSIONS
  Mast cells were identified in the choroid of all classes of vertebrates investigated except sharks. Their morphology, location, and staining characteristics were remarkably similar from teleost fish through to eutherian mammals and bore close morphological resemblance to mammalian connective tissue mast cells. The similar morphology and distribution of mast cells in the choroid of all vertebrate classes studied suggest a basic physiological function that has been retained since the evolution of the vertebrate eye.
authors: Department of Anatomy & Developmental Biology, School of Biomedical Sciences, Faculty of Medicine, Nursing and Health Sciences, Monash University, Wellington Road, Clayton, VIC 3800, Australia. paul.mcmenamin@monash.edu
authors: Paul Gerard
authors: PG
authors: McMenamin
authors: Emily
authors: E
authors: Polla
mesh_terms: D000818:Animals; D002829:Choroid / Q000166:cytology*; D008407:Mast Cells / Q000166:cytology*; D013045:Species Specificity; D014714:Vertebrates / Q000033:anatomy & histology* / Q000145:classification*
keywords: eye; immune cells; mast cells; morphology; uveal tract; vertebrates