Simultaneous snRNA&ATACseq characterizes specific innate immune memory 4712

Abstract Description We aimed to pinpoint the molecular mechanisms underlying specific innate immune memory by investigating the epigenetic and transcriptional changes that specifically occur in monocytes after allo-stimulation. B6.Rag-/- γc-/- (BRG) mice were immunized by ip injection of Balb/c irradiated splenocytes. Splenic monocytes were FACS sorted at 0-, 3-, 7- and 28-days post-immunization and from BRG mice injected with irradiated B6 splenocytes and allo-immunized BRG Pira-/- mice at day 7 after injection. Simultaneous snRNA&ATACseq was then performed. WNN UMAP projected 4 cell neighborhoods (N). N1 and N2 increased in abundance after allo-stimulation. N1 highly expressed genes encoding cell cycle proteins, Ly-6C, and PIR-A. Pseudotime and Real-time multiomic trajectory inference supported that N1 is a precursor subset that differentiates to downstream monocytes after allostimulation. N1 and its progeny acquired memory pathways specifically after allostimulation. Dynamic GRNi using Dictys revealed key transcription factors governing monocyte memory formation and response. EdU pulse chase, adoptive transfer, ddPCR, and phenotyping experiments confirmed the findings. Hence, specific innate immune memory is sourced from a monocyte precursor subset specifically responding to allo-stimulation with unique transcriptional and epigenetic changes that are passed down to its progeny. Funding Sources Supported by 2023 American Society of Transplantation Career Transition Grant (Grant #998676); NIAID R01 AI172973; NIAID R01 AI099465. Topic Categories Transplantation Immunology (TRAN)