Evaluating the Role of IL-17 as an Orchestrator of Peripheral-central Cross Talk in Depressive Symptoms

The investigators seek clinically actionable understanding of the mechanisms that underlie depression in the context of immune mediated inflammatory diseases (IMIDs), delivered by a focused immune intervention study examining brain circuitry using state of the art imaging in the context of exquisitely specific therapeutic immune interception in human immune disease. Glutamate concentration in the NAcc will be positively correlated with the magnitude of the inflammatory response and will be attenuated by IL-17A inhibition. Ultimately, this will be associated with an improvement in depressive symptoms. The strength of coupling between early and late systems will be attenuated in the context of IL-17A-driven inflammation and will be correlated with less frequent switching behaviour following negative outcomes and ultimately depressive symptoms. This coupling will be re-established following IL-17 antagonism. Patients whose depressive symptoms benefit most from IL-17A antagonism will exhibit greatest resting-state and task-specific functional connectivity between Th-NAcc.