Frey, B. F. | bioRxiv Science

bioRxiv2023

IL-2-induced Stat3 Signaling is Critical for Effector Treg Cell Programming

Maintenance of immune homeostasis to the intestinal mictrobiota is dependent on a population of effector regulatory T (eTreg) cells that develop from microbiota-reactive induced (i)Treg cells. A cardinal feature of eTreg cells is their production of IL-10, which plays a non-redundant role in immune tolerance of commensal microbes. Here, we identify an unexpected role for IL-2-induced Stat3 signaling to program iTreg cells for eTreg cell differentiation and Il10 transcriptional competency. IL-2 proved to be both necessary and sufficient for eTreg cell development - contingent on Stat3 output of the IL-2 receptor coordinate with IL-2 signaling during early Treg cell commitment. Induction of iTreg cell programming in absence of IL-2-induced Stat3 signaling resulted in impaired eTreg cell differentiation and a failure to produce IL-10. An IL-2 mutein with reduced affinity for the IL-2R{gamma} ({gamma}c) chain was found to have blunted IL-2R Stat3 output, resulting in a deficiency of Il10 transcriptional programming that could not be fully rescued by Stat3 signaling subsequent to an initial window of iTreg cell differentiation. These findings expose a heretofore unappreciated role of IL-2 signaling that acts early to program subsequent production of IL-10 by developing eTreg cells, with broad implications for IL-2-based therapeutic interventions in immune-mediated diseases.

immunology↗

bioRxiv2023

Fixation Before Dissociation Using a Deep Eutectic Solvent Preserves In Vivo States and Phospho-Signaling in Single-Cell Sequencing

Single-cell RNA-sequencing (scRNA-seq) presents an opportunity to deconstruct cellular networks but is limited by the loss of biological information, including in vivo cellular states and phospho-signaling. Herein, we present fixation before dissociation using a deep eutectic solvent (DES), which preserves multiple domains of in vivo biological data, including morphology, RNA, proteins, and post-translational modifications. In scRNA-seq of viable versus DES bone marrow, dissociation induced global stress responses, immune and stromal cell activation, and loss of highly sensitive cell populations, which were prevented with DES. Further, we introduce a validated and flexible method for performing intracellular CITE-seq in DES-fixed cells. Leveraging this approach during Th17 T cell stimulation allowed the simultaneous quantification of transcriptomes and four phosphorylated proteins, leading to the identification of a hyperactivated state in p-ERK/p-FOS double positive cells, which we experimentally validated. We anticipate that DES-based fixatives will allow the accurate reconstruction of in vivo cellular networks and uncover cooperativity amongst intracellular pathways.

immunology↗