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:associated lymphoid tissue (MALT), and in particular the intestinal immune system, develops immune tolerance to dietary antigens and components of the bacterial Xora to which epithelial tissues are exposed constantly (Dubois et al. 2003).
Category: