Mice that are unable either to make macrophages or to make them in sufficient numbers will protect themselves from bacterial infections in some other way

Mice that show elevated levels of nitrates can easily fight off most types of bacterial infections.

In mice, macrophages play a role in the production of nitrates or inhibit a process by which nitrates are broken down or otherwise eliminated.

When a healthy mouse becomes infected with an invasive organism, the number of macrophages in the mouse's body decreases.

Injections of nitrates into mice that lack macrophages will not enhance the ability of these animals' immune systems to fight off infection.