While the exact epistasis of Imd pathway signalling components is continually scrutinized, the mechanistic order of many key components of the pathway is well-established. The following sections discuss Imd signalling as it is found in Drosophila melanogaster, where it is exceptionally well-characterized. Imd signalling is activated by a series of steps from recognition of a bacterial substance (e.g. peptidoglycan) to the transmission of that signal leading to activation of the NF-κB transcription factor Relish. Activated Relish then forms dimers that move into the nucleus and bind to DNA leading to the transcription of antimicrobial peptides and other effectors.