Immunohistochemical observations of lysozyme in the Paneth cells of specific-pathogen-free and germ-free mice

The localization of lysozyme, which may function as an antibacterial agent, was immunohistochemically studied on the mouse Paneth cell secretory granules showing bipartite substructures (central core and peripheral halo). The lysozyme immunoreactivity was observed in the core, but not in the halo. Even in germ-free mice, Paneth cells have many secretory granules and their cores show lysozyme immunoreactivity. It seems likely that mice Paneth cells possess the ability to produce secretory granules containing lysozyme in disregard of the intestinal bacterial milieu.