Neutrophils Contribute to Severity of Tuberculosis Pathology and Recovery From Lung Damage Pre- and Posttreatment

Neutrophil-mediated (proportions of functional protective subtypes and reactive oxygen species generation capacity) tuberculosis susceptibility constitutes a strong scientific premise for future mechanistic and clinical studies targeting immunosuppressive host-directed therapies for tuberculosis disease progression and severity. Background Despite microbiological cure, about 50% of tuberculosis (TB) patients have poor lung recovery. Neutrophils are associated with lung pathology; however, CD16/CD62L-defined subsets have not been studied in TB. Using flow cytometry, we monitored frequencies, phenotype, and function of neutrophils following stimulation with Mycobacterium tuberculosis (Mtb) whole cell lysate (WCL) and ESAT-6/CFP-10 fusion protein (EC) in relation to lung pathology. Methods Fresh blood from 42 adult, human immunodeficiency virus (HIV)-negative TB patients were analyzed pre- and post-therapy, with disease severity determined using chest radiography and bacterial load. Flow cytometry was used to monitor frequencies, phenotype, and function (generation of reactive oxygen species [ROS], together with CD11b, tumor necrosis factor, and interleukin 10 [IL-10] expression) of neutrophils following 2-hour stimulation with Mtb-specific antigens. Results Total neutrophils decreased by post-treatment compared to baseline (P = .0059); however, CD16(br)CD62L(br) (segmented) neutrophils increased (P = .0031) and CD16(dim)CD62L(br) (banded) neutrophils decreased (P = .038). Banded neutrophils were lower in patients with severe lung damage at baseline (P = .035). Following WCL stimulation, ROS from segmented neutrophils was higher in patients with low Mtb loads even after adjusting for sex (P = .038), whereas IL-10-expressing CD16(dim)CD62L(lo) cells were higher in patients with mild damage (P = .0397) at baseline. Conclusions High ROS generation, low levels of banded neutrophils, and high levels of IL-10-expressing CD16(dim)CD62L(lo) neutrophils are associated with reduced lung pathology at diagnosis. Hence, neutrophils are potential early indicators of TB severity and promising targets for TB host-directed therapy.

Automated summary

The study used flow cytometry to monitor changes in neutrophils in the blood of tuberculosis patients before and after treatment, finding associations between high reactive oxygen species generation, low levels of banded neutrophils, and high levels of IL-10-expressing CD16(dim)CD62L(lo) neutrophils with reduced lung pathology, suggesting potential early indicators of tuberculosis severity.