| dc.description.abstract | The transcription factor Retinoic acid-related Orphan Receptor (ROR)-a has roles in metabolism, circadian rhythm and cellular development, such as Th17 cells and group 2 innate lymphoid cells (ILC2). The identification that RORa is critical for the development of ILC2s was discovered using the type 2 inducing helminth N. brasiliensis. Recently, there is accumulating evidence for a role of Rora in Th2 cells during inflammation. The aims of this study were to investigate the role of other RORa-expressing cells in immune responses to N. brasiliensis infection and HDM challenge, with particular focus on the development of lung Th2 cells. Infecting Rorasg/sg mice, which have a natural mutation in the gene encoding Rora resulting in a non-functional protein, with N. brasiliensis developed an altered type 2 immune response, characterised by a higher worm count in the small intestine and reduced lung ILC2s compared to WT mice. Interestingly, it was also observed that Rorasg/sg mice also have a reduced frequency of lung CD4 T cells, GATA3+CD4 T (Th2) cells and eosinophils following N. brasiliensis infection. To expand on these findings, Rorasg/sg mice were used to generate Rorasg/sg BM chimera mice to explore the role of Rora in cells from hematopoietic versus non-hematopoietic origin. Rorasg/sg BM chimera mice had a delayed N. brasiliensis expulsion and also had a reduced frequency of lung ILC2s, CD4 T cell, GATA3+CD4 T (Th2) cells and eosinophils following N. brasiliensis infection. Therefore, indicating that in addition to its known role in ILC2 development, RORa may have a role in Th2 and eosinophil development. A Rora reporter mouse was generated to detect Rora expressing cells by flow cytometry. Notably, following N. brasiliensis infection, there was increase in Rora expressing CD4 T cell, GATA3+CD4 T (Th2) cells in the lung. In addition, there was also an increase in Rora expressing CD4 T cells with an activated, TEM and tissue-resident phenotype, indicating a role for RORa in Th2 cell development, memory and activation following N. brasiliensis infection. To expand on these observations, the Cre-Lox recombination technology was used to generate Rorafl/flCD4Cre and Rorafl/flIl7raCre mice, which have Rora deleted from CD4 and Il7ra expressing cells, respectively. As previously reported, Rorafl/flIl7raCre mice had a reduced frequency of ILC2s and a delayed worm expulsion, whilst Rorafl/flCD4Cre mice had comparable frequency of ILC2s and worm expulsion with WT mice. However, interestingly, Rorafl/flCD4Cre mice had a reduced frequency of lung GATA3+CD4 T cells following N. brasiliensis infection, therefore indicating that Rora has a role in GATA3+CD4 T cell development independent of ILC2s. A second model of type 2 immunity was utilised, i.n. HDM challenge which induces lung inflammation. In support of the helminth generated results, both Rorasg/sg and Rorafl/flCD4Cre mice had reduced frequency of lung GATA3+CD4 T cells and Rora reporter mice had an increase in frequency of Rora expressing GATA3+CD4 T cells, activated TEM and tissue-resident CD4 T cells following HDM challenge. Furthermore, in vitro analysis revealed that naive CD4 T cells isolated from both Rorasg/sg and Rorafl/flCD4Cre mice had reduced ability to polarise towards GATA3+CD4 T cells. Therefore, further implicating a role of Rora in Th2 cell development. Therefore, taken together, the findings presented in this thesis identify a role for transcription factor RORa in activation and development of Th2 cells. Therefore, may provide possible therapeutic benefit for targeting Rora in helminth infections or allergic disorders such as asthma. | en |
