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:The downregulation of IL-12 and TNF-α by atRA could further redirect the immune balance toward immunoglobulin production and a humoral immune response as suggested by the studies in vitamin A deficient mice (53, 54) and the increased susceptibility of vitamin A deficient children to measles (7, 55).
Category: