IDO1 and disease arising from reactivation of latent virus: Rv1737c is predominantly expressed by the Mtb in latent infection. In this study, we have characterized the Rv1737c functions in the recruitment and activation of macrophages, which play a cardinal role in innate and adaptive immunity. Rv1737c induced the tolerogenic phenotype of macrophages by upregulating the expression of indoleamine-2,3-dioxygenase 1 (IDO1)