PhD Oral Exam - Catalina Marysol Caryasal Gonczi, Biology
Modulation of Helper T Cells by β2 Adrenergic Receptor Ligands in a PKA-Dependent Manner
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School of Graduate Studies
When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.
Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.
The adaptive immune system protects the body against pathogens. It is composed of multiple molecules and immune cells, such as helper T (Th) cells. One subtype of Th cells, Th17 cells, are of particular interest because they secrete IL-17A cytokine, which plays a role in autoimmune diseases. I focused on a hormone receptor called beta2-adrenergic receptor (β2AR), which modulates the adaptive immune system when stimulated with catecholamine hormones or adrenergic drug ligands. This receptor is a G-protein-coupled receptor that alters the cAMP pathway and PKA enzyme. My main hypothesis was that β2AR will modulate IL-17A in a cAMP and PKA-dependent manner.
The methods to test the hypothesis, blood mononuclear cells obtained from healthy human participants were used. Cells were activated in-vitro along with several chemical agonists or inhibitors of β2AR-cAMP-PKA-pathway. Enzyme-linked immunoassay was used to detect IL-17A secretion and intracellular flow cytometry for detecting IL-17A and RORγ (Th17 specific transcription factor). Th cells were purified from blood mononuclear cells to demonstrate the specificity of the response. To determine genetic factors influencing the Th17 response to adrenergic drugs, genomic DNA was sequenced and single nucleotide polymorphisms were determined in ADRB2, gene encoding β2AR.
The novel results were that Th17 cells expressed β2AR and that agonists (stimulatory ligands) of the receptor augmented IL-17A secretion as demonstrated in chapter 2. I further tested the involvement of the cAMP and PKA pathway in Th17 cells using a range of chemicals to suppress or augment the cell signalling pathway in chapter 3. Finally, I determined one of the genetic factors causing inter-individual variations in Th17 modulation and discovered a drug that can suppress Th17 cells in chapter 4.
In conclusion, I demonstrated that Th17 cells are modulated by β2AR because of cAMP-PKA pathway. I found that genetic factors alter the response. I discovered a drug that can suppress Th17 cells, a potential breakthrough for immunomodulatory treatment of autoimmune diseases. My thesis represents an early pre-clinical study that was meant to find new drug options to treat autoimmune diseases mediated by Th17 cells. My promising results will lead to future studies to assess safety and efficacy.