M. Matsuda et al., DEMONSTRATION AND ORGANIZATION OF DUCT-ASSOCIATED LYMPHOID-TISSUE (DALT) OF THE MAIN EXCRETORY DUCT IN THE MONKEY PAROTID-GLAND, Archives of histology and cytology, 60(5), 1997, pp. 493-502
Duct-associated lymphoid tissue (DALT) of the main excretory duct in t
he monkey parotid gland was first demonstrated by Light microscopy and
by transmission and scanning electron microscopy. The DALT included a
follicular area, a parafollicular area and a specialized overlying ep
ithelium with distinct fine-structural elements. There was usually a s
olitary lymphoid follicle located in the subepithelial area near the o
rifice of the parotid duct, The lymphoid follicles typically had a dis
tinct germinal center, Numerous immune cells often infiltrated into th
e epithelium overlying the lymphoid follicle. The superficial epitheli
al cells of the DALT were larger and flatter than the ordinary duct ep
ithelial cells, and had short irregular microvilli on their luminal su
rface, They were also in close contact with immune cells such as dendr
itic cells and lymphocytes. Goblet cells were rare in this area, In ad
dition, bacteria, seen at the duct orifice, were sometimes taken up by
the flattened epithelial cells near the orifice, Latex microspheres a
dministrated as particulate antigens at the duct orifice were selectiv
ely taken up by the flattened epithelial cells and also by the intraep
ithelial dendritic cells of the DALT. These morphological findings sug
gest that the epithelial cells of the DALT in parotid glands take up a
ntigens from the duct lumen and transport them to adjacent immune cell
s, and that the DALT in parotid glands may serve as one of the inducti
ve sites in the common mucosal immune system.