Despite microbiological cure, about 50% of 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 Mtb whole cell lysate (WCL) and ESAT-6/CFP-10 fusion protein (EC)) in relation to lung pathology.
Fresh blood from 42 adult, HIV-negative TB patients were analysed pre- and post-therapy, with disease severity determined using Chest X-Rays and bacterial load. Flow cytometry was used to monitor frequencies, phenotype and function (generation of ROS, together with CD11b, TNF and IL10 expression) of neutrophils following 2-hour stimulation with Mtb-specific antigens.
We show that total neutrophils decrease by treatment completion compared to baseline (p=0.0059); however, CD16 brCD62L br (segmented) neutrophils increase (p=0.0031) and CD16 dimCD62L br (banded) neutrophils decrease (p=0.038). Moreover, banded neutrophils are lower in patients with severe lung damage at baseline (p=0.035). Furthermore, we demonstrate that following WCL stimulation, ROS from segmented neutrophils is higher in patients with low Mtb loads even after adjusting for sex (p=0.038) while IL-10-expressing CD16 dimCD62L lo are higher in patients with mild damage (p=0.0397) at baseline. Patients showing good recovery from lung damage possess higher baseline granulocyte frequencies following WCL (p=0.042) and EC stimulation (p=0.011).
Hence, our results suggest that high ROS generation, low levels of banded neutrophils and high levels of IL10-expressing CD16 dimCD62L lo neutrophils are associated with reduced lung pathology at TB diagnosis. Hence, neutrophils are potential early indicators of TB severity and promising targets for TB host-directed therapy.

© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.

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