Changes occurring in the epithelium covering the bronchus-associated lymphoid tissue of rats after intratracheal challenge with horseradish peroxidase

Abstract

Changes occurring in the epithelium covering bronchus-associated lymphoid tissue (BALT) in the rat after several intratracheal administrations of horseradish peroxidase (HRP) were studied using morphological and ultrastructural methods. The epithelium is invaded by W3/25-positive (T-helper) lymphocytes, the BALT epithelial cells become Ia-positive and develop microvilli; there is an apparent loss of cilia. The number of non-ciliated cells in stimulated BALT increases. The non-ciliated cells can be subdivided into two cell types, one with electron-dense cytoplasm and cytoplasmic granules and the other without granules. The electron-density of the latter cell type is intermediate between that of the ciliated cells and that of the granule-containing non-ciliated cells. The granule-containing cell types may be responsible for the uptake of antigens, while the other non-ciliated cell may be involved in the production of the secretory component and the passage of secretory IgA.

A morphologic study of bronchus‐associated lymphoid tissue in turkeys

“…The BALT of turkeys is a true lymphoepithelial tissue composed of a specialized epithelium, a complex lymphocyte population, numerous cells with potential for antigen processing and presentation, and high endothelial venules. However, LE cells of turkey BALT do not appear to be structurally specialized for largescale endocytosis of material from the bronchial lumen, as proposed Lor BALT in other species (Racz et al, 1977;Tenner-Racz et al, 1979;van der Brugge-Gamelkoorn et al, 1986).…”

“…This specialized epithelium is referred to as a laymphoepithelium, reflecting the intimate physical association of epithelium and lymphocytes in these tissues (Fournier et al, 1977). In BALT of rabbits and rats, lymphoepithelial (LE) cells are squamous or cuboidal, non-ciliated, and have microvilli of irregular height and orientation (Bienenstock and Johnston, 1976;van der Brugge-Gamelkoorn et al, 1986;Tenner-Racz et al, 1979;Racz et al, 1977;Fournier et al, 1977). Apical vesicles are present in LE cells of rabbit BALT in which an active immune response has been stimulated (Racz et al, 1977;Tenner-Racz et al, 19791, but not in LE cells of unstimulated rabbit BALT (Bienenstock and Johnston 1976).…”

Respiratory Tract

“…Immunocytochemical study of the rat BALT following intratracheal challenge with horseradish peroxidase showed that the majority of cells that infiltrated the bronchial epithelium were T helper (CD4 positive) lymphocytes. 126 Furthermore, Ia antigen expression of the epithelial cells overlying the BALT was shown to increase, associated with an increase in the number and size of microvilli, a more pronounced glycocalyx and a decrease in number of cilia.…”

“…125 Single intratracheal doses of T cell-dependent antigens such as horseradish peroxidase, bovine serum albumin and BCG have been shown to produce only minor morphological changes which include expansion of the zone of lymphocytes immediately under the epithelium and infiltration of the bronchial epithelium overlying BALT by lymphocytes. 126 In addition, perivascular, peribronchial or alveolar infiltrates of small and large lymphocytes and macrophages were observed in the lungs of rats given BCG.…”

The role of bronchus-associated lymphoid tissue in respiratory immunity of chickens and turkeys: morphologic and functional studies

“…BALT epithelium is modified in ways that appear to compromise this barrier. In BALT of rabbits and rats, lymphoepithelial cells(LE) are squamous or cuboidal and non-ciliated(22,56,133,157,172). The apical cytoplasm of LE cells is often attenuated, such that only a thin rim of cytoplasm separates the external environment from subepithelial cells and tissues(22).Mucus-secreting cells are either absent or in low numbers over BALT lymphoid nodules(22,56,110,151,172).Specializations for uptake of luminal materials occur in BALT epithelial cells.…”