Defense strategies in human efferent tear ducts
F. Paulsen1, A. Thale2, U. Schaudig3, B. Tillmann1
Purpose: Dacryocystitis is the most frequent disease in the efferent lacrimal system. Only little is known about antimicorbial defense mechanisms in the efferent tear ducts. Aim of the present study was to analyze the human lacrimal passage under immunological aspects.
Methods: The human lacrimal sac and nasolacrimal duct were examined histologically, histochemically and immunohistochemically.
Results: Glycoproteins produced by goblet cells of the lacrimal passage were found to contain carbohydrates including fucose and sialic acid. In mucus Muc 2 was detected, whereas Muc 1 was absent. The presence of lysozym, lactoferrin, phospholipase A2 and secretory IgA in the cytoplasm of some of the apical epithelial cells was demonstrated. In more than one third of the cases was organized lymphoid tissue found with the cytomorphological and immunopheno-typical features of mucosa-associated lymphoid tissue (MALT). The other two thirds of the cases showed a diffuse infiltrate of defense cells within the lamina propria.
Conclusion: Synthesized mucins of goblet cells form a specialized protective layer on the epithelium of the lacrimal ducts, which functionally serves for a simplified drainage of tear fluid into the inferior meatus of the nose. Together with antimicrobial peptides and immunocompetent cells, the protective layer plays a role in antigen defense and prevents invasion of pathogenic agents. According to other regions of the human body organized MALT of the efferent tear ducts is named tear duct-associated lymphoid tissue (TALT). It is not present in the lacrimal passage of all humans and it is suggested that this lymphoid tissue may be acquired either in reaction to immunological changes of the lymphatic tissue inside the body or in reaction to specific infections.
1Anatomisches Institut der Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, D-24098 Kiel