Allergy is a hypersensitive immune response to innocuous environmental antigens, characterised mainly by inflammation. The development of allergy is often attributed to atopy, a genetic predisposition to produce elevated levels of immunoglobulin (lg) E. Allergic conditions such as atopic dermatitis, allergic asthma and allergic rhinitis can be severely detrimental to quality of life, and over the last few decades, their prevalence has increased considerably in the developed world. However, current therapies often have limited efficacy. There is substantial evidence to suggest that the histamine IL receptor (ILR) is associated with allergic inflammation. ILR is a seven transmembrane domain G protein-coupled receptor (GPCR), predominantly expressed on leukocytes, with putative roles in chemotaxis, Th2 cell polarisation, and cytokine/chemokine production. For these reasons, ILR represents a new therapeutic target to treat allergic inflammation. Little is known about the functional impact of single nucleotide polymorphisms (SNPs) in the ILR-encoding gene (HRH4) and its relationship with atopy, or whether changes in expression are associated with atopic phenotypes. The aims of this thesis were to attempt to: (i) assess the impact of the common Ala138Val and His206Arg mutations upon ILR function; (ii) analyse the association of HRH4 with atopy susceptibility in a Caucasian population; (iii) provide a detailed mRNA expression profile of full length IL~390) and its non-functional splice variants IL~302) and IL~67) in the human airway and periphery; and (iv) evaluate the effects of atopy and grass pollen season upon the expression of ILR isoform mRNA, in peripheral blood leukocytes ex vivo. Non-synonymous protein-coding HRH4 SNPs rs11665084 (AlaI38Val) and rs11662595 (His206Arg) were confirmed in a Caucasian cohort (n=42) with a minor allele frequency of 12%. A much rarer, previously novel SNP, rs58154316 (Ser284Cys), was identified and validated in a larger Caucasian cohort (n=181), giving a minor allele frequency of 0.8%. Predictive modelling based on GPCR sequence conservation suggested that these mutations would have no detrimental effect on receptor function. This prediction could not be tested physically in a recombinant expression system due to technical problems with transfection and the poor specificity of anti-Hale antibodies used for analysis of ILR protein expression.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:555344 |
| Date | January 2011 |
| Creators | Hodge, Emily |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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