Autonomous regeneration sequencers were technological devices utilized by the Borg, designed to instantly replace any component which may be removed as a form of attack. The Borg assimilated this technology from Species 259 in Galactic Cluster 3.
In 2374, the Borg installed these components aboard the USS Voyager, along with a number of other components, as part of their short-lived alliance against Species 8472. Later, when Lieutenant Torres and Ensign Kim were attempting to remove the Borg components from the ship's plasma intake manifolds, they encountered difficulties due to the fact that the components would simply replace themselves. Seven of Nine was eventually able to assist in their efforts by instructing them in the deactivation of the regeneration sequencers, which included disconnecting each sequencer conduit at the insertion juncture. (VOY: "Scorpion, Part II", "The Gift")