Carr, Allison R.

Abstract Introduction It is critical for the immune system to destroy cells harboring intracellular infection to remove pathogen burden. This function is widely attributed to cytotoxic T cells, which can physically engage with their targets through the T cell receptor complex, releasing cytotoxic granules, resulting in a specific death of infected targets. However, effector cytokines tumor necrosis factor-α (TNF) and interferon-γ (IFNγ), secreted by T cells, are themselves cytotoxic in combination to a degree. While TNF has appreciated cell death function through the TNF receptor 1 (TNFR1) signaling pathway, no clear cytotoxic function is attributed to IFNγ. Because of the diffusible nature of these cytokines, it is possible for T cells to elicit cytotoxicity without requiring direct contact with their targets, termed paracrine killing. Whether paracrine killing occurs during viral infection and how it is regulated is unclear. Paracrine killing poses issues of both sensitivity to these cytokines in that high concentrations of these cytokines are needed to affect target cells, as well as specificity in discriminating infected from uninfected host cells. Accounting for both issues, we hypothesize that paracrine killing is elicited through pathogen restriction whereby only infected cells are susceptible to death. Methods Analysis was performed in vitro using the Incucyte live cell imaging system and Western blots with fibroblast targets and a VSV infection model and OT1 T cells were leveraged ex vivo. Results TNF and IFNγ protect cells against the cytopathic effect of the virus. TNF specifically synergizes with VSV resulting in death of the infected cells and the two cytokines have distinct roles that work in concert. We demonstrate that TNF and IFNγ released by activated T cells suppress viral infection of nearby cells in a paracrine manner. Conclusion Here we provide insight and context into how distinct cytokines function in a cooperative manner for immune protection during an infection. Funding Source Mayo Clinic Graduate School of Biomedical Sciences Topic Categories Viral Immunology (VIR)

Cytotoxic T cells produce the cytokine interferon-γ (IFN-γ). We sought to determine whether IFN-γ directly kills target cells and found that T cells used IFN-γ to kill murine melanoma cells lacking the kinases TBK1 and IKKε. In the absence of both kinases, IFN-γ induced the production of TNF receptor 1 (TNFR1) and the sensor Z-DNA binding protein 1 (ZBP1) in the tumor cells to stimulate receptor-interacting protein kinase 1 (RIPK1)–dependent apoptosis in a cell-autonomous manner. IFN-γ also enhanced the activation of nuclear factor κB (NF-κB) signaling in a TNFR1-dependent manner in cells deficient in both TBK1 and IKKε. Because IFN-γ–induced apoptosis occurred in a transcription-dependent manner with slow kinetics, STAT1 and NF-κB cooperated to activate the expression of inflammatory genes in the dying cells. Thus, IFN-γ–induced cell death was accompanied by an inflammatory signature in the absence of TBK1 and IKKε. TBK1 and IKKε not only mediated the induction of type I IFN but also inhibited RIPK1-dependent death and NF-κB–dependent inflammation. Therefore, we propose that these kinases may have gained these intertwined functions so that cells infected by pathogens that produce antagonists of TBK1 and IKKε are eliminated by IFN-γ–secreting T cells in an inflammatory manner to compensate for the inhibition of type I IFN production.

ABSTRACT Cytotoxic T lymphocytes (CTLs) are known to eliminate target cells through perforin-mediated, contact-dependent killing - a process limited by the number of effector T cells despite its serial nature. CTLs likely also possess a mass killing mechanism that can eliminate target cells more efficiently. Using CAR-T cells against B7H3 present on B16 tumor targets, we demonstrate that activated T cells can also kill targets in a perforin-independent manner by releasing diffusible TNF and IFNγ capable of killing nearby targets in a paracrine fashion even if they bear no antigen. Against an unperturbed target, paracrine killing is inefficient but is enhanced by the deletion of TNFR1 signaling molecules such as TAK1, HOIP, or TBK1/IKKε. Notably, these molecules are inhibited naturally by pathogen-encoded antagonists. Expression of a microbial-encoded antagonist, such as the Yersinia -encoded YopJ that antagonizes TAK1 or Ebola-encoded VP35 that antagonizes TBK1/IKKε, alters the target cell response to these cytokines from non-lethal to lethal. We propose that target cells are inherently resistant to killing by TNF and IFNγ, but the presence of a microbial factor alters this sensitivity, providing for the selective elimination of the infected cell while minimizing harm to uninfected bystander cells. We propose the term ‘pathogen-restriction’ to describe this discriminatory mechanism. Potentially, any microbial-derived factor that crosstalks with the TNF and IFNγ signaling pathways can function as a pathogen-restriction element. GRAPHICAL ABSTRACT Short Summary T cells use TNF and IFNγ to kill target cells in a paracrine manner where target elimination is restricted by the presence of pathogen-derived factors.

Abstract Medical researchers are increasingly prioritizing the inclusion of underserved communities in clinical studies. However, mere inclusion is not enough. People from underserved communities frequently experience chronic stress that may lead to accelerated biological aging and early morbidity and mortality. It is our hope and intent that the medical community come together to engineer improved health outcomes for vulnerable populations. Here, we introduce Health Equity Engineering (HEE), a comprehensive scientific framework to guide research on the development of tools to identify individuals at risk of poor health outcomes due to chronic stress, the integration of these tools within existing healthcare system infrastructures, and a robust assessment of their effectiveness and sustainability. HEE is anchored in the premise that strategic intervention at the individual level, tailored to the needs of the most at-risk people, can pave the way for achieving equitable health standards at a broader population level. HEE provides a scientific framework guiding health equity research to equip the medical community with a robust set of tools to enhance health equity for current and future generations.

Abstract Waldenstrom macroglobulinemia (WM) and its precursor IgM gammopathy are distinct disorders characterized by clonal mature IgM-expressing B-cell outgrowth in the bone marrow. Here, we show by high-dimensional single-cell immunogenomic profiling of patient samples that these disorders originate in the setting of global B-cell compartment alterations, characterized by expansion of genomically aberrant extrafollicular B cells of the nonmalignant clonotype. Alterations in the immune microenvironment preceding malignant clonal expansion include myeloid inflammation and naïve B- and T-cell depletion. Host response to these early lesions involves clone-specific T-cell immunity that may include MYD88 mutation–specific responses. Hematopoietic progenitors carry the oncogenic MYD88 mutations characteristic of the malignant WM clone. These data support a model for WM pathogenesis wherein oncogenic alterations and signaling in progenitors, myeloid inflammation, and global alterations in extrafollicular B cells create the milieu promoting extranodal pattern of growth in differentiated malignant cells. Significance: These data provide evidence that growth of the malignant clone in WM is preceded by expansion of extrafollicular B cells, myeloid inflammation, and immune dysfunction in the preneoplastic phase. These changes may be related in part to MYD88 oncogenic signaling in pre–B progenitor cells and suggest a novel model for WM pathogenesis. This article is highlighted in the In This Issue feature, p. 549