Author ORCID Identifier

0000-0002-1848-5494

Date of Graduation

5-2022

Document Type

Dissertation (PhD)

Program Affiliation

Immunology

Degree Name

Doctor of Philosophy (PhD)

Advisor/Committee Chair

Stephanie S. Watowich, PhD

Committee Member

Min Chen, PhD

Committee Member

Gregory Lizee, PhD

Committee Member

Margarida Albuquerque Almeida Santos, PhD

Committee Member

Pamela Wenzel, PhD

Abstract

Dendritic cells (DCs) are specialized innate immune cells that sense pathogen-associated signals via pattern recognition receptors, including the TLRs, and subsequently stimulate adaptive immune responses to combat infection. The mutual antagonists and transcriptional regulators inhibitor of DNA binding 2 (Id2) and the E protein E2-2 direct type 1 conventional DC (cDC1) and plasmacytoid DC (pDC) development, respectively. Though the requirement of Id2 in cDC1 lineage development during the steady state is well established, roles for Id2 in DC subset or progenitor response to TLR agonists remains unknown. Prior work found Id2 is induced in pDCs upon maturation, suggesting Id2 may be an important regulator of pDC function and that TLR agonist signaling directly regulates Id2 gene expression. It also remains unknown whether TLR agonist-regulated Id2 is important in other DC populations, including the DC progenitor compartment and cDC1s. Therefore, we hypothesize TLR agonist signaling regulates Id2 induction, affecting both DC lineage development and the unique effector functions of pDCs and cDC1s. Herein, we found Id2 expression correlates with pDC maturation upon TLR agonist treatment, modestly regulates proinflammatory soluble factor production, but is largely dispensable for their maturation. We further determined mechanisms of Id2 gene regulation via molecular assays and genetic mouse models. TLR activation of the E2 ubiquitin-conjugating enzyme Ubc13, rapidly stimulates Id2 transcriptional activity, independent of type I IFN (IFN-I) signaling in pDCs. Based on this mechanism, we further assessed roles for TLR agonists in related DC populations. We found TLR agonist treatment induces Id2 expression in CD115+ common DC progenitors (CDPs), but not cDC1s. To study the impact of Id2 in the DC progenitor compartment upon TLR agonist treatment, we utilized both in vitro differentiation assays and in vivo TLR agonist challenges and found Id2 is essential for cDC1 development following TLR challenge. Finally, using Id2 conditional deletion, we identified specific roles for Id2 to modestly promote CXCL2 production from CD103+ cDC1s, though Id2 was largely dispensable for their maturation. Collectively, we conclude Id2 predominately exerts its role as a developmental regulator of the cDC1 lineage, but also regulates the production of specific cytokines or chemokines in a DC subset-specific manner. Furthermore, we found TLR agonists stimulate Id2 transcription in a cell-type specific manner via Ubc13, which may be an important regulatory pathway in other immune or non-immune cells.

Keywords

dendritic cells, TLRs, Id2, pDCs, cDC1s, dendritic cell progenitors, transcriptional regulation, cell activation

Available for download on Friday, April 28, 2023

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