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Background: Mucosa-associated lymphoid tissue (MALT) plays a central role in mucosal immunity. Whereas the characteristics and function of MALT in the intestine are well established, almost nothing is known about MALT in the larynx., Methods: In this study we examined the morphology and the lymphocyte subset composition of MALT in the larynges of children who had died of sudden infant death or various defined traumatic or nontraumatic causes., Results: Organized lymphoid tissue was found in the supraglottic parts of the larynx in nearly 80% of the children in both groups. This lymphoid tissue showed all morphological signs of MALT, such as typical lymphoid follicles with germinal centers, infiltration of the overlying epithelium by lymphocytes, and high endothelial venules (HEV). Thus we will use the term LALT (larynx-associated lymphoid tissue) to refer to this tissue. The lymphoid follicles of LALT contained mainly B lymphocytes with some CD4+ lymphocytes in the germinal centers. Remarkably, T lymphocytes of both subset types and B lymphocytes were observed in comparable numbers in the parafollicular area., Conclusions: We assume that LALT is a physiological structure of the larynx in young children. The morphology and the distribution of lymphocyte subsets are similar to those of MALT in the human gut. LALT may be a regular part of the mucosal immune system in young children with the role of respiratory inductive site for mucosal immunity.

Background: The larynx is a complex organ composed of different connective tissue elements. So far, the extracellular matrix of the larynx has not been thoroughly described. Hyaluronan is a matrix polysaccharide with physicochemical effects and biological cell functions in soft connective tissues., Methods: The histochemical distribution of hyaluronan (hyaluronic acid, hyaluronate) was studied in tissue sections from various levels of the rabbit larynx by means of a hyaluronan-binding protein and avidin biotin peroxidase staining. Microwave-aided fixation was used to retain the extracellular location of hyaluronan., Results: Hyaluronan accumulated chiefly in the subepithelial lamina propria and in the connective tissue enclosing striated muscle fibres of the thyroarytenoid muscle and vocalis muscle. This localization contrasted sharply with the weak staining for hyaluronan in muscles external to the thyroid cartilage. Intensive staining for hyaluronan was found in perivascular and periglandular connective tissue, as in the vacuoles of the hyaline cartilage of the thyroid, cricoid and arytenoid cartilages, and to a lesser extent in the lacunae of the chondrocytes and in the perichondrium of the elastic cartilage of the epiglottis., Conclusions: Hyaluronan was heterogenously distributed in the rabbit larynx. It was abundant in intrinsic laryngeal muscles performing small, precise, and rapid movements and in the subepithelium at the glottic level, where it may facilitate mucosal movements. The abundant hyaluronan in the subglottic region may be involved in the control of vascular leakage and edema formation.