PhD, University of Cincinnati, 2023, Medicine: Immunology

Cognate interaction between effector memory CD4+ T cells (TEM) and dendritic cells (DCs) induces innate inflammatory cytokine production, resulting in detrimental outcomes such as autoimmune pathology and cytokine storms. We previously established that TEM cells use TNF superfamily ligands to activate DCs, yet whether this interaction with DCs induces other cell intrinsic changes that influence inflammatory responses by DCs has never been investigated. Here we have made a surprising discovery that TEM cells trigger double-strand DNA breaks via mitochondrial ROS production in interacting DCs. Initiation of the DNA damage response in DCs leads to activation of a cGAS-independent, non-canonical STING-TRAF6-NFκB signaling axis. Consequently, STING deficient DCs display reduced NFκB activation leading to significant defects in transcriptional induction and functional production of IL-1β and IL-6 following their interaction with TEM cells, both in vitro and in vivo. The discovery of TEM cell-induced innate inflammation through DNA damage and a non-canonical STING-NFκB pathway presents this pathway as a potential target to alleviate T cell driven inflammation in autoimmunity and cytokine storms.

Committee: Chandrashekhar Pasare Ph.D. (Committee Chair); Jonathan Katz Ph.D. (Committee Member); Sing Sing Way M.D. Ph.D. (Committee Member); William Miller Ph.D. (Committee Member); Daniel Starczynowski Ph.D. (Committee Member); Leah Claire Kottyan Ph.D. (Committee Member) Subjects: Immunology

Doctor of Philosophy, Case Western Reserve University, 2008, Pathology

Proper expression of pro-inflammatory genes, including ELR+ CXC chemokines, is achieved through regulation of transcription and post-transcriptional processes including mRNA decay. Modulation of transcription is an important means of achieving stimulus-induced expression and the mechanisms of this response have been well-characterized. mRNA stability is becoming increasingly recognized as a critical factor influencing expression of these genes. The mRNAs are constitutively unstable, but are stabilized in response to a variety of stimuli to allow robust expression.IL-17-induced gene expression has emerged as a critical factor driving inflammation in both host defense and autoimmunity. However, the molecular mechanisms by which IL-17 regulates expression are poorly understood. IL-17 alone has little effect on gene expression, but induces a synergistic response in combination with TNFα. We have determined that this observation is explained by the finding that IL-17 has relatively little effect on transcription, but rather works primarily through mRNA stabilization. It thus cooperates with TNFα, which drives transcription but is unable to prolong mRNA half-life, by providing a distinct requirement for gene expression. Although the adaptors Act1 and TRAF6 have both been previously reported to be essential for IL-17-induced responses, we find that only Act1 is involved in mRNA stabilization. Taken together our finds indicate the existence of a novel signaling pathway downstream of Act1 that is responsible for mRNA stabilization and plays a central role in IL-17-induced gene expression. The finding that IL-17-induced stabilization does not require TRAF6 raised questions regarding the role of this adaptor in IL-1α-induced mRNA stabilization. Although all IL-1α driven responses previously examined, including NF-κB and MAP kinase activation, require TRAF6, surprisingly we have found that TRAF6 is not required for IL-1α-induced mRNA stabilization. The signals leading to these (open full item for complete abstract)

Committee: Thomas Hamilton PhD (Advisor); Clifford Harding MD/PhD (Committee Chair); Ganes Sen PhD (Committee Member); George Dubyak PhD (Committee Member); Clive Hamlin PhD (Committee Member) Subjects: Immunology; Pathology