Abstract
Complex barriers separate immune-privileged tissues from the circulation. Here, we propose that cell entry to immune-privileged sites through barriers composed of tight junction-interconnected endothelium is associated with destructive inflammation, whereas border structures comprised of fenestrated vasculature enveloped by tightly regulated epithelium serve as active and selective immune-skewing gates in the steady state. Based on emerging knowledge of the central nervous system and information from other immune-privileged sites, we propose that these sites are endowed either with absolute endothelial-based barriers and epithelial gates that enable selective and educative transfer of trafficking leukocytes or with selective epithelial gates only.
Publication types
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Research Support, Non-U.S. Gov't
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Review
MeSH terms
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Animals
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Blood-Aqueous Barrier / immunology
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Blood-Aqueous Barrier / physiology
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Blood-Brain Barrier / immunology
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Blood-Brain Barrier / physiology
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Blood-Retinal Barrier / immunology
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Blood-Retinal Barrier / physiology
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Blood-Testis Barrier / immunology
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Blood-Testis Barrier / physiology
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Cell Fusion
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Chemotaxis, Leukocyte*
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Chimerism
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Epithelial Cells / physiology
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Epithelial Cells / ultrastructure
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Epithelium / immunology
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Epithelium / physiology
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Female
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Humans
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Immune Tolerance / immunology
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Immunologic Surveillance / immunology
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Immunologic Surveillance / physiology*
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Inflammation / immunology
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Inflammation / physiopathology
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Male
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Maternal-Fetal Exchange / immunology
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Models, Immunological*
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Neutrophil Infiltration
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Organ Specificity
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Pregnancy
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Tight Junctions / physiology*
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Transendothelial and Transepithelial Migration / physiology