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:…implicated the MEK/ERK signalling pathway in IFN-γ-stimulated iNOS expression; thus, exposure of microglial/ macrophage cells to this cytokine in the presence of MEK or ERK inhibitors inhibited the effect of IFN-γ (Blanchette et al., 2003; Han et al., 2003; Park et al., 2005; Shen et al., 2005).
Category: