Investigation of enteric neuron and type 2 lymphocyte interactions at homeostasis and during Nippostrongylus brasiliensis infection

Type 2 lymphocyte responses are vital for mediating immunity to parasitic helminths and establishing wound repair. Key lymphocytes – type 2 innate lymphoid cells (ILC2s) and T helper 2 (Th2) cells – express the effector cytokines IL-4, IL-5, and IL-13 which drive the canonical “weep and sweep” responses that are critical for resistance to parasitic helminth infections. Emerging evidence indicates neuropeptides, such as Neuromedin U (NMU), as salient regulators of ILC2s. The bona fide sources of these neuropeptides has not been verified, with reciprocal interactions between ILC2s and distinct enteric neuronal populations not yet explored. In this thesis, a population of murine enteric neurons was identified as a meaningful player in the regulation of type 2 lymphocyte responses in steady-state conditions and after infection with *Nippostrongylus brasiliensis* (*N. brasiliensis*). Analysis of publicly available single cell RNA-sequencing data revealed one subset of enteric cholinergic neurons, termed NMU-ergic neurons, which express genes encoding known regulators of ILC2s (*Nmu*, *Calcb*, *Chat*) as well as molecules (*Il13ra1*, *Il4ra*, *Il7*) not previously implicated in intestinal neuro-immune interactions. Generation of a mouse strain, *Nmu^Cre-iRFP670*, enabled the interrogation of how NMU-ergic neurons regulate type 2 immunity. Confocal microscopy imaging of tissues from an *Nmu^Cre-iRFP670* fate mapper revealed that ILC2s closely associate with enteric NMU-ergic in either steady-state conditions or after infection with *N. brasiliensis*. Conditional deletion of *Il4ra* or *Il7* in NMU-ergic neurons established novel mechanisms of intestinal neuro-immune interactions. Flow cytometric analysis of lymphocytes following *Il4ra* deletion in NMU-ergic neurons unveiled an interesting mechanism by which type 2 cytokines can affect NMU-ergic neuronal regulation of ILC2 and Th2 cell responses across different mucosal sites during infection with *N. brasiliensis*. Furthermore, flow cytometric analysis of lymphocyte populations following *Il7* deletion in NMU-ergic neurons demonstrated that these neurons represent a novel and important source of IL-7 for lymphocytes at steady-state conditions, but not during *N. brasiliensis* infection. To further dissect the dynamic interactions between NMU-ergic neurons and ILC2s, a chemogenetic system using Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) was established using the *Nmu^Cre-iRFP670* strain. The establishment and study of *Nmu^Cre-iRFP670* strain has elucidated a significant intestinal neuro-immune circuit for the regulation and potentiation of type 2 immune responses.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Ko, Michelle

Advisor dc:contributor.advisor

• McKenzie, Andrew

• ILC2
• neuroimmune
• type 2 immunity

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/aac24894-edb5-421f-9084-761ea49ae0b9/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.104675

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/362553