While our previous experiments with primary human macrophages indicated a requirement for live infection with ESAT-6 expressing bacteria and cytosolic delivery of the protein (10), Kumar et al. studying both murine BMDMs and RAW264.7 cells found that exposure to soluble recombinant ESAT-6 protein alone was sufficient to trigger HO-1 expression (50). The gene discussed is HMOX1; the disease is infection.