Exploring the role of neutrophils in infectious and noninfectious pulmonary disorders

Abstract

With the change in global environment, respiratory disorders are becoming more threatening to the health of people all over the world. These diseases are closely linked to performance of immune system. Within the innate arm of immune system, Neutrophils are an important moiety to serve as an immune defense barrier. They are one of the first cells recruited to the site of infection and plays a critical role in pathogenesis of various pulmonary diseases. It is established that the migration and activation of neutrophils can lead to inflammation either directly or indirectly and this inflammation caused is very crucial for the clearance of pathogens and resolution of infection. However, the immunopathological mechanisms involved to carry out the same is very complex and not well understood. Despite there being studies concentrating on the role of neutrophils in multiple respiratory diseases, there is still a long way to go in order to completely understand the complexity of the participation of neutrophils and mechanisms involved in the development of these respiratory diseases. In the present article, we have reviewed the literature to comprehensively provide an insight in the current development and advancements about the role of neutrophils in infectious respiratory disorders including viral respiratory disorders such as Coronavirus disease (COVID-19) and bacterial pulmonary disorders with a focused review on pulmonary tuberculosis as well as in noninfectious disorders like Chronic obstructive pulmonary disease (COPD) and asthma. Also, future directions into research and therapeutic targets have been discussed for further exploration.

Graphical Abstract

PLAIN LANGUAGE SUMMARY

Respiratory illnesses are becoming more prevalent and a substantial source of sickness and mortality worldwide as a result of the changes in the global environment. Although diagnostic and therapeutic approaches for respiratory disorders have improved over the years, a thorough and in-depth approach is still required to understand the underlying immuno-pathophysiological mechanisms. Neutrophils are a crucial part of innate immune system which functions as a first line defense against various pulmonary infections. They are known to be involved in resistance against invading pulmonary pathogens and also play an important role in repairing of damaged lung tissue by removing debris. However, emerging evidences suggest that neutrophils may also be involved in promoting and aggravating the unabating inflammation in several pulmonary disorders by release of various proteases, forming neutrophil extracellular traps or by attracting and activating other immune cells at the site of inflammation. In this article, we have discussed diverse roles and responses of neutrophils and their use in potential future research and therapeutic approaches in infectious pulmonary disorders like Tuberculosis and COVID-19 and noninfectious pulmonary disorders like Chronic obstructive pulmonary disease (COPD) and asthma.

Keywords:

• Asthma
• COPD
• COVID-19
• neutrophils
• pulmonary disorders
• tuberculosis

Author contribution statement

All the authors have contributed equally in the formation of manuscript.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work is financially supported by Indian council of Medical Research, New Delhi [61/3/2018-BMS]. Alisha Arora is gratefully acknowledging the support of Council of Scientific and Industrial Research, India for Research fellowship under 09/006(0501)/2019-EMR-IThe authors are thankful to All India Institute of Medical Sciences, New Delhi, India for their support.