IL4 and neoplasm: Macrophages are highly plastic immune cells that display a range of phenotypic and functional properties.7,38 To test whether an acidic tumour milieu can influence macrophage phenotype, we used zwitterionic buffer-based medium to stimulate BMDMs using IFN-γ/LPS and IL-4 for 24 h at pH 7.4 or 6.8.