Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Induction of the complement cascade in the brain, particularly in myeloid-derived cells such as microglia/monocytes, has been shown to be a potentially damaging event in aging and disease [28,29,30,31].
Category: