To investigate whether SLPI is involved in susceptibility to UPEC-caused UTI, we utilized 129;BL/6 SLPItm1Smw/J mice (28), which are engineered to lack SLPI, and back-crossed them onto a C57BL/6J background for at least 10 generations (Slpi−/− mice). This evidence concerns the gene SLPI and bacterial urinary tract infection.