Dear Sebastian, thank you very much for pointing out these additional connections. Your points are well taken. However, with respect to your last point, I would like to mention that our data do not address at all the issue of the possible host cell affected by SopE to caspase-1 signalling in vivo. The macrophage system employed here merely served the purpose of answering one question: can SopE activate caspase-1 in the absence of flagellin? For technical reasons, macrophages provided the cleanest in vitro system to address this (we simply did not have a useful epithelial cell model to do this experiment properly). Our earlier in vivo data using bone marrow chimeric mice lacking caspase-1 in all bone marrow derived cells argue, that the actual signaling from SopE to caspase-1 should occur in epithelial cells (Müller et al., 2009).
