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Nadja Knop, Erich Knop; Conjunctiva-Associated Lymphoid Tissue in the Human Eye. Invest. Ophthalmol. Vis. Sci. 2000;41(6):1270-1279. doi: https://doi.org/.
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purpose. Mucosa-associated lymphoid tissue (MALT) represents a part of the
immune system located at mucosal surfaces. Its presence in the human
eye is the point in question in the current study. Its occurrence,
components, topography, and probable functional significance in the
human conjunctiva and lacrimal drainage system were investigated.
methods. Fifty-three complete conjunctival sacs were obtained from cadaveric
eyes, prepared as flat wholemounts, stained, optically cleared,
observed in total thickness, and sectioned for light microscopic
histology, immunohistochemistry, and electron microscopy. Eight
lacrimal sacs and adhering canaliculi were prepared accordingly.
results. Lymphoid tissue was mainly observed in the palpebral conjunctiva, more
pronounced in the upper than in the lower lid. It occurred in different
forms: 1) In all specimens, diffuse lymphoid tissue of lymphocytes and
plasma cells, most of which were IgA positive, formed a thin layer in
the lamina propria. The overlying epithelium produced secretory
component. 2) In approximately three fifths of the conjunctival sacs,
organized follicular accumulations were embedded in this layer. They
had a lenticular shape, were composed of B lymphocytes, and were
apically covered by lymphoepithelium. 3) Both types could be associated
with the conjunctival crypts. Lymphoid tissue with similar
characteristics, including secondary follicles, was also observed
inside the lacrimal drainage system. High endothelial venules were
present in all types of lymphoid tissue.
conclusions. Human conjunctiva and lacrimal drainage system show an associated
lymphoid tissue (suggesting the term conjunctiva-associated lymphoid
tissue [CALT]) that contains all components necessary for a complete
immune response. Expression of immunoglobulins and secretory component
indicates that the conjunctiva belongs to the secretory immune
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