NOS2 and listeriosis: In the context of systemic Listeria monocytogenes infection CCR2-dependent, TNF- and iNOS-producing DCs (Tip-DC) were found to play an essential role in innate defense against intracellular bacteria [31], a finding that has been extended to other intracellular pathogens, for example Leishmania and Toxoplasma[28], [30], [55], [56].