Macrophages play a central role in the regulation of inflammation and it was hypothesised that investigation of the effect of IFN-γ on the behaviour of macrophages during P. aeruginosa infection could provide information regarding the potential benefits of an IFN-γ-driven inflammatory response against P. aeruginosa. GM-CSF was included in the study because of its established activating effect on myeloid cell function [28,29] and the reported correlation between high serum GM-CSF with increased IFN-γ expression and better pulmonary function in CF patients [6]. The gene discussed is CSF2; the disease is cystic fibrosis.