Assessment of Immune and Molecular Changes in T Lymphocytes, Natural Killer Cells and Vasoactive Neuropeptides in Chronic Fatigue Syndrome

  • Ekua Brenu

Student thesis: Doctoral Thesis


Immune dysregulation due to infection, inflammation or compromises to immune and molecular mechanisms can have detrimental effects on normal physiological functions. Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) is a disorder of unknown mechanism where diagnosis is often delayed and evidence-based effective treatments are lacking. CFS/ME is characterised by severe fatigue, flu-like symptoms, pain and cognitive disturbances. To date a mechanism explaining the relationship between these symptoms and the physiological irregularities presented by patients remains obscure. As such, CFS/ME patients spend a considerable amount of money on health service cost in pursuit of the most effective treatment to alleviate their symptoms. An important initiative towards better management of CFS/ME is the development of accurate diagnosis. The principal aim of this research is to identify feasible biomarkers that can be used in effective diagnosis of CFS/ME. This research examines the status of lymphocytes in CFS/ME with a specific focus on their cellular function including apoptosis, protein secretion, receptor expression and gene expression. It is hypothesized that irregularities in these cellular processes contribute to the mechanism of CFS/ME and thus may form a suite of diagnostic markers for assessing CFS/ME patients. Participants for the study comprised 95 CFS/ME patients and 50 non-fatigued controls at baseline. Data for 50 CFS/ME and 27 non-fatigued controls was available for the follow up study at 6 and 12 months. Participants were aged between 25-65 years. The criteria for inclusion were based on the Centre for Disease Prevention and Control (CDC) 1994 clinical diagnostic criteria. Whole blood was collected from each participant at baseline, at 6 months and at 12 months. Flow cytometric protocols were employed in examining measures of cytotoxic activity in CD8+T and Natural Killer (NK) cells, levels of CD56brightCD16negative NK cells CD56dimCD16positive NK phenotypes, CD4+T helper cytokine secretion and levels of Foxp3 and vasoactive neuropeptide receptor (VPACR2). The expression pattern of cytotoxic related genes including granzyme A (GZMA), granzyme K (GZMK), perforin (PRF1) and interferon-gamma (IFN-G) and the expression of microRNA (miRNA) molecules in NK and CD8+T cells were investigated. At baseline, compared to the non-fatigued controls, CFS/ME patients exhibited significant decreases in cytotoxic activity of NK and CD8+T cells, levels of CD56brightCD16negative NK cells and repression of IFN-G, GZMA and GZMK gene expression. At the same time, significant increases in cytokines, IL-10, IFN-γ and TNF-α, FOXP3, VPACR2 and PRF1expression were noticed in the CFS/ME patients compared to controls. At 6 months follow up, significant reductions in NK activity, CD56brightCD16negative NK cells, IL-10 and IL-17A were observed in the CFS/ME patients compared to the non-fatigued controls. At 12 months, in contrast to the nonfatigued controls, CFS/ME patients continued to demonstrate significant decreases in NK activity and significant increases in only IL-2. Assessment of miRNA expression revealed a significant down-regulation of a number of miRNAs in CFS/ME patients in comparison to the non-fatigued controls, specifically, miR-21, miR-146a, miR-223, miR-17-5p, miR-103, miR-106, miR-10a, miR-191 and miR-152 were significantly down-regulated mainly in the CFS/ME patients in comparison to the controls. In conclusion, the results from this study have elucidated the extent of decreases in cytotoxic activity in CFS/ME. In addition, this study has identified unique immune related processes and molecules that are compromised in CFS/ME patients. These novel parameters may have important implications in the development of biomarkers for CFS/ME. Moreover the consistent decrease in cytotoxic activity and NK phenotypes over the 12 month period strongly supports their usefulness as biomarkers for diagnosing CFS/ME. These biomarkers if implemented in the clinical setting could potentially assist in improving diagnosis and demonstrating a clear pathomechanism for CFS/ME. Eventually, this may result in the development of better therapeutic and treatment strategies for managing CFS/ME.
Date of Award9 Jun 2012
Original languageEnglish
SupervisorSonya Marshall-Gradisnik (Supervisor) & Kevin John Ashton (Supervisor)

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