NLRP3 and bacterial urinary tract infection: We also found that variation in hemolysin expression by UPEC can have profound effects on biological outcomes; low-level hemolysin expression triggers NLRP3-mediated macrophage cell death that is associated with host protection in a mouse model of experimental UTI, whereas high-level hemolysin expression triggers NLRP3-independent macrophage cell death and increased bladder colonization (32).