Control of pathogens by formation of abscesses and granulomas is a major strategy of the innate immune system, especially when effector mechanisms of adaptive immunity are insufficient. We show in human listeriosis that DCs expressing indoleamine 2,3-dioxygenase (IDO), together with macrophages, are major cellular components of suppurative granulomas in vivo. Induction of IDO by DCs is a cell-autonomous response to Listeria monocytogenes infection and was also observed in other granulomatous infections with intracellular bacteria, such as Bartonella henselae. Reporting on our use of the clinically applied anti–TNF-α antibody infliximab, we further demonstrate in vitro that IDO induction is TNF-α dependent. Repression of IDO therefore might result in exacerbation of granulomatous diseases observed during anti–TNF-α therapy. These findings place IDO+ DCs not only at the intersection of innate and adaptive immunity but also at the forefront of bacterial containment in granulomatous infections.
Alexey Popov, Zeinab Abdullah, Claudia Wickenhauser, Tomo Saric, Julia Driesen, Franz-Georg Hanisch, Eugen Domann, Emma Lloyd Raven, Oliver Dehus, Corinna Hermann, Daniela Eggle, Svenja Debey, Trinad Chakraborty, Martin Krönke, Olaf Utermöhlen, Joachim L. Schultze