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Complex immune system changes are observed within the first hour after traumatic injury

PLOS

Within the first hour after a person experiences a traumatic injury, their immune system undergoes a series of complex, dynamic changes, according to a new study published in PLOS Medicine by Jon Hazeldine, of the University of Birmingham, UK, and colleagues.

Many trauma victims who survive their initial injury die later of multi-organ dysfunction or sepsis, complications related to the massive immune response mounted by the body after trauma. Much of what is known about this immune response is based on blood samples taken from patients after admission the hospital, generally hours after trauma. An ongoing question in the field has been whether immune activation and suppression happen simultaneously or one after the other. In the new study, researchers collected blood samples from 89 adult trauma patients at a regional trauma network in the West Midlands, UK, within an hour of their injury (mean time to sample 42 minutes, range 17-60 minutes). Levels of immune cells in those samples, as well as samples collected at later time points, were measured and patient outcomes were tracked.

The researchers observed that within minutes of a traumatic injury, levels of many immune cells and molecules were altered--in some cases, increasing compared to normal and in other cases decreasing. These changes reflected both innate immune cell activation and immune suppression, suggesting that both processes are being induced simultaneously. Many of the characteristics of the immune reaction observed in the first hour after trauma were different than those seen at later time points. Moreover, the researchers found an association between natural killer T cell numbers in the hour after trauma and the eventual development of multiple organ dysfunction syndrome.

"Our study highlights how differences in sample timing can influence our understanding of the post-injury immune response," the authors say. The results, they add, also underscore "the dynamic nature of the immune response to trauma and show at the functional and phenotypic level that immune alterations consistent with activation and suppression are evident within 1-hour of injury."

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Funding:

For funding this research, the authors acknowledge the National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre, which is joint funded by the Department of Health and Ministry of Defence (http://www.nihr.ac.uk; JH, DNN, ET, DD, JRBB, ZS, NC, AB, and JML), the Scar Free Foundation Birmingham Burns Research Centre, which is part of the Burns Collective within the Scar Free Foundation (http://www.scarfree.org.uk; PHam, RJD, and PHar), the RoseTrees Trust (http://www.rosetreestrust.co.uk; JH, AB, and JML; grant number, DTAA.RDBU18237), and the Medical Neuroscience Teaching and Research Fund (https://sites.google.com/site/mntrfund/; JH, AB, and JML; grant number, DTAA.RCLG19305). The authors would also like to acknowledge the Queen Elizabeth Hospital Birmingham Charity for funding the purchase of the Sysmex XN-1000 haematology analyser (https://www.qehb.org; PHar). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests:

The authors have declared that no competing interests exist.

Citation:

Hazeldine J, Naumann DN, Toman E, Davies D, Bishop JRB, Su Z, et al. (2017) Prehospital immune responses and development of multiple organ dysfunction syndrome following traumatic injury: A prospective cohort study. PLoS Med 14(7): e1002338. https://doi.org/10.1371/journal.pmed.1002338

Author Affiliations:

Institute of Inflammation and Ageing, University of Birmingham, Birmingham, United Kingdom

NIHR Surgical Reconstruction and Microbiology Research Centre, Queen Elizabeth Hospital Birmingham, Birmingham, United Kingdom

Scar Free Foundation, Birmingham Centre for Burns Research, Birmingham, United Kingdom

Midlands Air Ambulance, Unit 16 Enterprise Trading Estate, Brierley Hill, West Midlands, United Kingdom

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