Helminth infections tend to be endemic in regions with a high incidence of pulmonary tuberculosis and have a modulatory effect on immune responses to Mycobacteria tuberculosis. In the Journal of Clinical Investigation, Khader and colleagues assess mice coinfected with the helminth Schistosoma mansoni and M. tuberculosis. Preinfection with S. mansoni or vaccination with S. mansoni egg antigen reversibly impairs M. tuberculosis–specific type 1 helper T cell responses, and lung inflammation. Furthermore, latent M. tuberculosis is reactivated by vaccination with S. mansoni egg antigen. The exacerbated lung inflammation is strongly dependent on the presence of arginase-1-positive macrophages. Finally, using outbred mice with a spectrum of M. tuberculosis–dependent pulmonary inflammation, the authors show that the expression of arginase-1 is proportional to disease severity even in the absence of helminth coinfection. These results thus shed light on how helminths can enhance the severity of tuberculosis.

J. Clin. Invest. 125, 4699–4713 (2015)