Genetic and Immunological Mechanisms Regulating Neuroinflammation

Multiple Sclerosis (MS) is the most common neurological disorder in young adults and imposes both health and socioeconomic burdens on society. The cause and aetiology of MS are incompletely understood and current treatments are inadequate. Pathologically, prolonged chronic inflammation and widespread demyelination in the central nervous system leads to atrophy and progressive worsening of disease. This thesis combined use of in vivo animal models, in vitro cellular assays and in silico computational methods to characterise pathogenic mechanisms and translate findings from models to human disease. The animal model of MS, experimental autoimmune encephalomyelitis (EAE), was evaluated in light of novel findings in MS aetiology and further analyzed to explore differences in strain susceptibility. Susceptible rats had increased interleukin 7 receptor (Il7r) and Il2ra expression as well as altered isoform signatures in naïve lymphoid tissue, setting the stage for T cell differentiation towards pathogenic T helper 1 (TH1) and TH17 subtypes. Moreover, increased Il18r1 expression described in susceptible rats was explored in MS. Dysregulation of this receptor can mediate disease initiation through T cell differentiation as well as T cell and macrophage activation. IL18R1 levels were increased in peripheral immune and central nervous tissues in MS. Inflammatory molecules that are dysregulated in EAE likely represent true pathogenic mechanisms in humans. Multiple approaches were used to define tumour necrosis factor (TNF) regulation of disease severity. A region on chromosome 4 in the rat regulated TNF production in macrophages following innate inflammatory stimulation. Additional inflammatory molecules were also genetically regulated, modifying the cellular phenotype and severity of multiple diseases. This specific inflammatory control provides insight into disease pathogenesis and future treatment options. The approach of combining genetic and immunological approaches in both models and human samples will continue to improve disease understanding and provide novel therapeutics through identification of key regulators and general immune and non-immune pathways. LIST OF PUBLICATIONS This thesis is based on the following papers, which are referred to in the text by their Roman numerals. I. Melanie Thessen Hedreul*, Alan Gillett*, Tomas Olsson, Maja Jagodic and Robert A. Harris. Characterization of Multiple Sclerosis candidate gene expression kinetics in rat experimental autoimmune encephalomyelitis. Journal of Neuroimmunology. 2009;210(1-2):30-9. II. Alan Gillett, Klio Maratou, Chris Fewings, Robert A. Harris, Maja Jagodic, Tim Aitman and Tomas Olsson. Alternative splicing and transcriptome profiling of experimental autoimmune encephalomyelitis using genome-wide exon arrays. PLoS One. 2009;4(11):e7773. III. Alan Gillett, Monica Marta, Tao Jin, Jonatan Tuncel, Patrick Leclerc, Rita Nohra, Stefan Lange, Rikard Holmdahl, Tomas Olsson, Robert A. Harris and Maja Jagodic. TNF production in macrophages is genetically determined and regulates inflammatory disease in rats. Journal of Immunology. 2010;185(1):442-50. IV. Alan Gillett*, Melanie Thessen Hedreul*, Mohsen Khademi, Alexander Espinosa, Amennai Daniel Beyeen, Maja Jagodic, Ingrid Kockum, Robert A Harris and Tomas Olsson. Interleukin 18 Receptor 1 expression distinguishes MS patients. Multiple Sclerosis. 2010;16(9):1056-65. *These authors contributed equally to the work