Early and opposing neutrophil and CD4 T cell responses shape pulmonary tuberculosis pathology.

Abstract

Pulmonary Mycobacterium tuberculosis (Mtb) infection results in a variety of heterogeneous lesion structures, from necrotic granulomas to alveolitis, but the mechanisms regulating their development remain unclear. Using a mouse model of concomitant immunity and subsequent aerosol infection, we demonstrate that counter regulation between neutrophils and CD4 T cells occurs very early during infection and governs these distinct pathologies. In primary Mtb infection, a dysregulated feed-forward circuit of neutrophil recruitment occurs, in which neutrophils hinder CD4 T cell interactions with infected macrophages, cause granuloma necrosis, and establish a replicative niche that drives a two-log increase in lung bacterial burden. Conversely, the rapid recruitment and activation of T cells due to concomitant immunity promotes local macrophage activation and dampens detrimental neutrophil responses. Together, these studies uncover fundamental determinants of tuberculosis lung pathology, which have important implications for new strategies to prevent or treat tuberculosis.