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Title: Immunomodulatory roles of par-2 in innate and adaptive immune responses
Author: Steven, Rachael
Awarding Body: University of the West of Scotland
Current Institution: University of the West of Scotland
Date of Award: 2012
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PAR-2 is a GPCR activated in response to proteolytic cleavage of the N terminus. Previous studies have revealed a critical role for PAR-2 in a murine arthritic model, reporting PAR-2 KO mice are resistant to disease. Further studies have identified PAR-2 on rheumatoid synovial CD68+ macrophages. Also, ex vivo studies revealed blockade of PAR-2 using a specific antagonist results in substantial reduction of many pro-inflammatory cytokines, known to contribute to rheumatoid pathology including IL-1β, IL-6 and TNFα. Although these studies clearly identify PAR-2 as having a role in disease, the cellular mechanisms involved require elucidation. This doctoral project therefore focuses on identifying the effects of PAR-2 activation/blockade in immunological responses of innate and adaptive cells which are thought to play a pivotal role in inflammatory disease pathology. In order to assess the role of PAR-2 in innate and adaptive immune systems, studies were carried out to determine the key differences between PAR-2 WT and KO macrophage and T cell populations. Cellular markers, cytokine release and populations of T cells in peripheral lymphoid organs were assessed. The PAR-2 murine studies also comprised an in vivo component to assess and compare innate cell recruitment in an innate model of peritoneal inflammation induced by thioglycollate. The later stages of the thesis focused on human studies by examination of buffy coat derived innate and adaptive cells. Characterisation of PAR-2 expression in these cell types and effect of PAR-2 activation/blockade on innate responses was determined by analysis of cytokine production, cell surface markers and morphological studies. Key results from these investigations identified an important role for PAR-2 in innate cell recruitment with significantly reduced macrophage numbers in PAR-2 KO in the thioglycollate model. PAR-2 KO derived macrophages also had significantly reduced expression of co-stimulatory markers, whilst the responses and proliferation of murine ova specific T cells (OT2) were significantly reduced in PAR-2 KO mice. Human studies identified PAR-2 expression in human macrophages, B and T cells. PAR-2 antagonism during monocyte to macrophage maturation resulted in impaired cellular maturation as determined by significantly decreased cell area in both M1 and M2 type macrophages. In addition to this, PAR-2 activation in M1 macrophages significantly upregulated HLA-DR, an antigen presenting molecule, haplotypes of which have been highly associated with increased risk of rheumatoid disease. Stimulations of these cells with a panel of TLR agonists revealed significant differences in TNFα when stimulated with the addition of PAR-2 agonist or antagonist. Human B and T cells were also analysed for PAR-2 expression, which was dramatically upregulated in response to pro-inflammatory stimuli. These data add to the existing literature supporting a role for PAR-2 in innate cell development and activation. This doctoral project highlights a role for PAR-2 in macrophage development, and recruitment of inflammatory cells, clearly identifying an important role for PAR-2 in innate immunology. In addition to this, the data generated is strongly supportive of a role for PAR-2 in adaptive cell responses, not only by indirect effects on innate cells but also direct effects on the adaptive cells themselves. This data is also relevant to studies of autoimmune disease, by investigating the potential pathological role of PAR-2 in arthritis. The data suggests that the PAR-2 mediated mechanism, responsible for the amelioration of arthritis in KO mice, may involve reduced macrophage activation, recruitment and pro-inflammatory cytokine release. The data also provides evidence for a role for PAR-2 in T cell specific responses, thought to be critical in RA disease.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available