I am talking about macrophage polarization studies conducted with mouse models. Three types of mouse models have been used for studying macrophage polarization: KO, BALB/c and C57Bl/6. Due to a deletion in the promoter region of Arg transporter gene, Slc7a2, of macrophages of C57BL/6, making them genetically resistant to M2 polarization and biased to M1 polarization (PMID: 23460752). On the contrary, BALB/c mice are considered as TH2-biased mice strain (PMID: 15489639).

Is there any unbiased mouse strain available?