The membrane-bound TLR2/4 and the cytosolic NOD1/2 play key roles in host innate defense-associated protection against microbial infection by sensing the presence of microbial pathogens including both extracellular and intracellular bacteria (29, 31, 33, 34), while deficiency in either TLR2/4 or NOD1/2 show an increased susceptibility to infections caused by a variety of bacteria (6, 9, 21, 23, 30). Here, NOD1 is linked to infection.