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Memory T and B cells in tissues are essential for protective immunity. Here, we performed a comprehensive analysis of the tissue distribution, phenotype, durability, and transcriptional profile of COVID-19 mRNA vaccine-induced immune memory across blood, lymphoid organs, and lungs obtained from 63 vaccinated organ donors aged 23-86, some of whom experienced SARS-CoV-2 infection. Spike (S)-reactive memory T cells were detected in lymphoid organs and lungs and variably expressed tissue-resident markers based on infection history, and S-reactive B cells comprised class-switched memory cells resident in lymphoid organs. Compared with blood, S-reactive tissue memory T cells persisted for longer times post-vaccination and were more prevalent with age. S-reactive T cells displayed site-specific subset compositions and functions: regulatory cell profiles were enriched in tissues, while effector and cytolytic profiles were more abundant in circulation. Our findings reveal functional compartmentalization of vaccine-induced T cell memory where surveilling effectors and in situ regulatory responses confer protection with minimal tissue damage., Competing Interests: Declaration of interests A.S. is a consultant for Gritstone Bio, Flow Pharma, Moderna, AstraZeneca, Qiagen, Fortress, Gilead, Sanofi, Merck, RiverVest, MedaCorp, Turnstone, NA Vaccine Institute, Emervax, Gerson Lehrman Group, and Guggenheim. La Jolla Institute. has filed for patent protection for various aspects of T cell epitope and vaccine design work. Columbia University has filed patent applications related to vaccine tissue assays., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Circulating memory CD8 T cell trafficking and protective capacity during liver-stage malaria infection remains undefined. We find that effector memory CD8 T cells (Tem) infiltrate the liver within 6 hours after malarial or bacterial infections and mediate pathogen clearance. Tem recruitment coincides with rapid transcriptional upregulation of inflammatory genes in Plasmodium-infected livers. Recruitment requires CD8 T cell-intrinsic LFA-1 expression and the presence of liver phagocytes. Rapid Tem liver infiltration is distinct from recruitment to other non-lymphoid tissues in that it occurs both in the absence of liver tissue resident memory "sensing-and-alarm" function and ∼42 hours earlier than in lung infection by influenza virus. These data demonstrate relevance for Tem in protection against malaria and provide generalizable mechanistic insights germane to control of liver infections., Competing Interests: Declarations of interests The authors declare no competing interests., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Microbial exposures can define an individual's basal immune state. Cohousing specific pathogen-free (SPF) mice with pet store mice, which harbor numerous infectious microbes, results in global changes to the immune system, including increased circulating phagocytes and elevated inflammatory cytokines. How these differences in the basal immune state influence the acute response to systemic infection is unclear. Cohoused mice exhibit enhanced protection from virulent Listeria monocytogenes (LM) infection, but increased morbidity and mortality to polymicrobial sepsis. Cohoused mice have more TLR2 + and TLR4 + phagocytes, enhancing recognition of microbes through pattern-recognition receptors. However, the response to a TLR2 ligand is muted in cohoused mice, whereas the response to a TLR4 ligand is greatly amplified, suggesting a basis for the distinct response to Listeria monocytogenes and sepsis. Our data illustrate how microbial exposure can enhance the immune response to unrelated challenges but also increase the risk of immunopathology from a severe cytokine storm., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)