Phagocytic cells in the taste buds of rat circumvallate papillae after denervation

Phagocytic cells in the taste buds of rat circumvallate papillae after the sectioning of bilateral glossopharyngeal nerves were examined by electron microscopy and immunohistochemistry. Electron micrographs taken 1 day after denervation revealed that flat-shaped cells were present just beneath the taste buds and that their cellular processes extended toward the debris from the degenerating taste buds. At 2-6 days after denervation, long and thin processes of the flat cells surrounded the debris and appeared to have taken them up into the cytoplasm as small vesicles. Evidence for phagocytosis by the flat cells was seen up to 9 days after denervation and again at 24 and 40 days, in correlation to the degeneration and regeneration of the taste buds. Pre-embedding immunohistochemistry using anti-vimentin antibody showed that flat cells strongly reacted with vimentin. Light microscopic immunohistochemistry using anti-macrophage antibodies (ED1, ED2) showed that throughout the post-operative days macrophages were not present underneath or within the taste buds. Most of the ED2-immunoreactive resident macrophages were located in the deep layer of connective tissue, and a few were found in the nerve bundle. ED1-immunoreactive cells were seen in the duct cells of von Ebner's glands and a few were in the trench wall of circumvallate papillae; however, they were also immunoreactive for anti-OX62 antibody, which recognizes dendritic cells. The results indicate that the phagocytic cells of the taste buds are fibroblasts, not macrophages. Moreover, resident macrophages participate in phagocytosis of degenerated nerves together with Schwann cells.