Immune biomarkers predicting clinical outcomes for major trauma patients

Saleem, A

Abstract

Major trauma continues to be the most common cause of death in the population under the age of 40 in England. Despite advances in trauma care in the UK, sepsis and multiple organ dysfunction syndrome (MODS) continue to be severe complications of trauma worldwide. Ongoing research exploring the immune response to trauma over the years has highlighted the systemic inflammatory response syndrome (SIRS) as an early immune response to trauma. Driven mainly via macrophages and innate immune cells, this response is followed by the counter anti-inflammatory response syndrome (CARS), mediated predominantly by T regulatory cells, in order to restore immune homeostasis.

The ‘two-hit theory’ proposes a link between MODS and an imbalance between proinflammatory and counter inflammatory responses, during which, an overexpression of SIRS results in early MODS and an overexpression of CARS results in late MODS, sepsis or septic shock. The suppressive abilities of T reg cells and the role they may play in this immune response is an area of great interest as early identification of T reg activity within the CARS response may act as a predictive biomarker of late MODS and poor clinical outcome.

This study aims to analyse the trends of 7 subsets of T lymphocytes; CD3+, CD4+, CD8+, CD25BRI, CD4+FOXP3+, CD25BRIFOXP3+, and CD127LOWFOXP3+ following major trauma, in the hopes of utilizing these as predictive biomarkers in the future of trauma care. Poor clinical outcome was represented in this study by a Sequential organ failure assessment (SOFA) score of greater than 1. In order to explore the relationship between CD markers, particularly T reg cells, and other mediators of inflammation, all CD markers used in this study were also tested against interleukin 6 (IL-6) and IL-10.

Prior to this study, blood samples from a cohort of 85 patients were gathered by Basmah Allarakia and Matthew Jones from the Central Manchester Foundation Trust (CMFT) and Salford Royal Foundation Trust (SRFT). Laboratory procedures were then carried out by Basmah Allarakia, during which, peripheral blood mononuclear cells were isolated, retrieved, and enriched. Immunofluorescent staining of T cell surface markers was done using fluorochrome labelled antibodies, before finally being analysed using FACS Verse flow cytometry.

During this study, T lymphocyte expression was analysed using the SPSS statistical software. A Spearman’s rank correlation test highlighted a significant correlation between CD3+ expression on Day 1 and SOFA scores on Day 5 (p= 0.007). A significant correlation between CD3+, CD25BRIFOXP3+ and CD127LOWFOXP3+ on Day 3 against SOFA scores on Day 5 was also found (p=0.02, p=0.049 and p=0.048 respectively). Furthermore, a paired T test highlighted that CD25BRIFOXP3+ and CD127LOWFOXP3+ displayed higher expression on Day 1 in those patients who developed SOFA scores >1 on Day 5, in comparison to patients who developed SOFA scores <1 on Day 5. These differences were also found to be significant (p= 0.05 and p= 0.03 respectively). A second Spearman’s rank correlation test also displayed a significant correlation between CD3+ and IL-10 on Day 3 (p= 0.000). furthermore, a significant correlation between both CD25BRIFOXP3+ and CD127LOWFOXP3+ and IL-6 on Day 3 was also found (p= 0.026 and p= 0.029 respectively).

Overall, significant findings were displayed regarding the role of T reg cells and their ability to be used as predictive biomarkers in the future of trauma care. Correlating to previous research, a higher expression of T regs was seen in patients who later developed a higher SOFA score, thus a poorer clinical outcome. The suppression mechanisms of T regs which may explain these results have been grouped into four main categories, these are; metabolic disruption, cytolysis, inhibitory cytokines such as interleukin-35 (IL-35), IL-10, and transforming growth factor- (TGF-), and finally, suppression by modulation of dendritic cell function or maturation.

The correlation between T regs and IL-6 also provide promising potential for the future of biomarker research, however a larger patient cohort and greater statistical analysis of these two immune markers must be carried out in order to confirm the validity of these findings.

Citation

Saleem, A. Immune biomarkers predicting clinical outcomes for major trauma patients. (Dissertation). University of Salford

• Thesis Type: Dissertation
• Deposit Date: Feb 5, 2021
• Publicly Available Date: Feb 5, 2021
• Award Date: Dec 1, 2020