A protective role for eosinophils in host resistance to Mycobacterium tuberculosis

Host resistance to Mycobacterium tuberculosis (Mtb) infection requires the activities of multiple leukocyte subsets, yet the roles of the different innate effector cells during tuberculosis (TB) are incompletely understood. Here we show a role for eosinophils in host resistance to Mtb infection. In humans, eosinophils are found in resected human TB lung lesions and autopsy granulomas. Eosinophils are also found in granulomas in zebrafish, mice, and non-human primates, where they are functionally activated and degranulate. Transcriptional profiling of lung tissue after Mtb infection of mice, that selectively lack eosinophils, revealed changes in neuronal associated pathways. Importantly, employing several independent models of eosinophil deficiency in mice, we demonstrate that eosinophils are required for optimal pulmonary bacterial control and host survival after Mtb infection. Collectively, our findings establish an unexpected role for eosinophils, granulocytes typically associated with type II inflammation, in host resistance against Mtb, a major human bacterial pathogen. Overall design: 18 C57BL/6 mouses with and without eosinophils were infected with TB