Pneumonia bacteria phagocyted by neutrophils

In this unique label-free footage obtained from a demo at the Infection and Immunity lab of the UMC in Utrecht, a culture of neutrophils can be seen phagocyting pneumonia bacteria. An image was obtained every 1.9s for 4 minutes and 45 seconds. We can clearly distinguish the different structures of the neutrophils, from their multi-lobulated nucleus to the phagosomes formed as a result of the phagocytic process.

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Pneumonia is an acute respiratory infection of either one or both lungs [1]. It is primarily caused by bacteria or viruses, although it can be caused by fungi and parasites as well.

Commonly isolated bacteria causing pneumonia are Streptococcus pneumoniae, Hemophilus influenzae, Chlamydophila pneumoniae and Mycoplasma pneumoniae [2]. Only S. pneumoniae is responsible for nearly 50% of cases [2].

Viral pneumonia, on the other hand, is frequently caused by rhinoviruses, coronaviruses, influenza virus, respiratory syncytial virus, adenovirus and parainfluenza[3,4]. Recently, an outbreak of SARS coronavirus 2, a new virus that can progress to pneumonia in infected individuals and that is conventionally known as COVID-19, has been declared a Public Health Emergency of International Concern by the WHO[5].

The immune mechanisms involved in pneumonia infections differs depending on the etiology of the disease. While in viral infections, mononuclear cells are the cellular type frequently linked to the inflammation[6], in bacterial infections neutrophils are key to the progression of the illness[7].

Neutrophils are granulocytes that have a characteristic multilobed nucleus, usually ranging from 3 to 5 interconnected lobes[8]. They combat pathogens in a non-specific way, as they take part in innate immune system[7]. After neutrophils migrate toward sites of infection or inflammation via chemotaxis, they help amplify inflammatory reactions by recruiting and activating other cells of the immune system and attack micro-organisms by phagocytosis, degranulation or neutrophil extracellular traps[9].

Discover more host-pathogen interaction videos on our dedicated page: Host-Pathogen Interactions >

 

[1] World Health Organization (2019, 2 August). Fact sheets: Pneumonia.

[2] Sharma S, Maycher B, Eschun G (May 2007). “Radiological imaging in pneumonia: recent innovations”. Current Opinion in Pulmonary Medicine13 (3): 159–69.

[3] Ruuskanen O, Lahti E, Jennings LC, Murdoch DR (April 2011). “Viral pneumonia”. Lancet377 (9773): 1264–75

[4] Figueiredo LT (September 2009). “Viral pneumonia: epidemiological, clinical, pathophysiological and therapeutic aspects”. Jornal Brasileiro de Pneumologia35 (9): 899–906

[5] World Health Organization (2020, 3 March). Rolling updates on coronavirus disease (COVID-19).

[6] Fleisher, Gary R.; Ludwig, Stephen, eds. (2010). Textbook of pediatric emergency medicine (6th ed.). Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins Health. p. 914

[7] Balamayooran, G., Batra, S., Fessler, M. B., Happel, K. I., & Jeyaseelan, S. (2010). Mechanisms of neutrophil accumulation in the lungs against bacteria. American journal of respiratory cell and molecular biology43(1), 5–16. https://doi.org/10.1165/rcmb.2009-0047TR

[8] Veda, P. (2011). Why are Neutrophils Polymorphonuclear? European Journal of Inflammation, 85–93.

[9] Selders, G. S., Fetz, A. E., Radic, M. Z., & Bowlin, G. L. (2017). An overview of the role of neutrophils in innate immunity, inflammation and host-biomaterial integration. Regenerative biomaterials4(1), 55–68. https://doi.org/10.1093/rb/rbw041

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