- The wild-derived inbred mouse strain SPRET/Ei is resistant to LPS and defective in IFN-beta production. Mahieu, T., Park, J.M., Revets, H., Pasche, B., Lengeling, A., Staelens, J., Wullaert, A., Vanlaere, I., Hochepied, T., van Roy, F., Karin, M., Libert, C. Proc. Natl. Acad. Sci. U.S.A. (2006)