Annual review of immunology最新文献

The role of the autoimmune regulator (Aire) in central immune tolerance and thymic self-representation was first described more than 20 years ago, but fascinating new insights into its biology continue to emerge, particularly in the era of advanced single-cell genomics. We briefly describe the role of human genetics in the discovery of Aire, as well as insights into its function gained from genotype-phenotype correlations and the spectrum of Aire-associated autoimmunity-including insights from patients with Aire mutations with broad and diverse implications for human health. We then highlight emerging trends in Aire biology, focusing on three topic areas. First, we discuss medullary thymic epithelial diversity and the role of Aire in thymic epithelial development. Second, we highlight recent developments regarding the molecular mechanisms of Aire and its binding partners. Finally, we describe the rapidly evolving biology of the identity and function of extrathymic Aire-expressing cells (eTACs), and a novel eTAC subset called Janus cells, as well as their potential roles in immune homeostasis.

Elite controllers are a heterogeneous group of people living with HIV who control viral replication without antiretroviral therapy. There is substantial evidence that at least some elite controllers are infected with replication-competent virus, thus they may serve as a model of a functional cure of HIV. The mechanisms responsible for virologic control have been actively studied. The most objective data support CD8+ T cell-based mechanisms of control, but other immune responses, mediated by antibodies and natural killer cells, may also play a role in controlling viral replication. In this article, we review the evidence for different mechanisms of immune control in these remarkable individuals.

Poxviruses have evolved a wide array of mechanisms to evade the immune response, and we provide an overview of the different immunomodulatory strategies. Poxviruses prevent the recognition of viral DNA that triggers the immune responses and inhibit signaling pathways within the infected cell. A unique feature of poxviruses is the production of secreted proteins that mimic cytokines and cytokine receptors, acting as decoy receptors to neutralize the activity of cytokines and chemokines. The capacity of these proteins to evade cellular immune responses by inhibiting cytokine activation is complemented by poxviruses' strategies to block natural killer cells and cytotoxic T cells, often through interfering with antigen presentation pathways. Mechanisms that target complement activation are also encoded by poxviruses. Virus-encoded proteins that target immune molecules and pathways play a major role in immune modulation, and their contribution to viral pathogenesis, facilitating virus replication or preventing immunopathology, is discussed.

The kidneys are life-sustaining organs that are vital to removing waste from our bodies. Because of their anatomic position and high blood flow, the kidneys are vulnerable to damage due to infections and autoinflammatory conditions. Even now, our knowledge of immune responses in the kidney is surprisingly rudimentary. Studying kidney-specific immune events is challenging because of the poor regenerative capacity of the nephrons, accumulation of uremic toxins, and hypoxia- and arterial blood pressure-mediated changes, all of which have unexpected positive or negative impacts on the immune response in the kidney. Kidney-specific defense confers protection against pathogens. On the other hand, unresolved inflammation leads to kidney damage and fibrosis. Interleukin-17 is a proinflammatory cytokine that has been linked to immunity against pathogens and pathogenesis of autoinflammatory diseases. In this review, we discuss current knowledge of IL-17 activities in the kidney in the context of infections, autoinflammatory diseases, and renal fibrosis.

The intestinal epithelium, which segregates the highly stimulatory lumen from the underlying tissue, harbors one of the largest lymphocyte populations in the body, intestinal intraepithelial lymphocytes (IELs). IELs must balance tolerance, resistance, and tissue protection to maintain epithelial homeostasis and barrier integrity. This review discusses the ontogeny, environmental imprinting, T cell receptor (TCR) repertoire, and function of intestinal IELs. Despite distinct developmental pathways, IEL subsets share core traits including an epithelium-adapted profile, innate-like properties, cytotoxic potential, and limited TCR diversity. IELs also receive important developmental and functional cues through interactions with epithelial cells, microbiota, and dietary components. The restricted TCR diversity of IELs suggests that a limited set of intestinal antigens drives IEL responses, with potential functional consequences. Finally, IELs play a key role in promoting homeostatic immunity and epithelial barrier integrity but can become pathogenic upon dysregulation. Therefore, IELs represent intriguing but underexamined therapeutic targets for inflammatory diseases and cancer.

Gastrointestinal nematode (GIN) infection has applied significant evolutionary pressure to the mammalian immune system and remains a global economic and human health burden. Upon infection, type 2 immune sentinels activate a common antihelminth response that mobilizes and remodels the intestinal tissue for effector function; however, there is growing appreciation of the impact GIN infection also has on the distal tissue immune state. Indeed, this effect is observed even in tissues through which GINs never transit. This review highlights how GIN infection modulates systemic immunity through (a) induction of host resistance and tolerance responses, (b) secretion of immunomodulatory products, and (c) interaction with the intestinal microbiome. It also discusses the direct consequences that changes to distal tissue immunity can have for concurrent and subsequent infection, chronic noncommunicable diseases, and vaccination efficacy.

Alzheimer disease (AD) is the most common neurodegenerative disease, and with no efficient curative treatment available, its medical, social, and economic burdens are expected to dramatically increase. AD is historically characterized by amyloid β (Aβ) plaques and tau neurofibrillary tangles, but over the last 25 years chronic immune activation has been identified as an important factor contributing to AD pathogenesis. In this article, we review recent and important advances in our understanding of the significance of immune activation in the development of AD. We describe how brain-resident macrophages, the microglia, are able to detect Aβ species and be activated, as well as the consequences of activated microglia in AD pathogenesis. We discuss transcriptional changes of microglia in AD, their unique heterogeneity in humans, and emerging strategies to study human microglia. Finally, we expose, beyond Aβ and microglia, the role of peripheral signals and different cell types in immune activation.

T cell responses must be balanced to ensure adequate protection against malignant transformation and an array of pathogens while also limiting damage to healthy cells and preventing autoimmunity. T cell exhaustion serves as a regulatory mechanism to limit the activity and effector function of T cells undergoing chronic antigen stimulation. Exhausted T cells exhibit poor proliferative potential; high inhibitory receptor expression; altered transcriptome, epigenome, and metabolism; and, most importantly, reduced effector function. While exhaustion helps to restrain damage caused by aberrant T cells in settings of autoimmune disease, it also limits the ability of cells to respond against persistent infection and cancer, leading to disease progression. Here we review the process of T cell exhaustion, detailing the key characteristics and drivers as well as highlighting our current understanding of the underlying transcriptional and epigenetic programming. We also discuss how exhaustion can be targeted to enhance T cell functionality in cancer.

The COVID-19 pandemic was caused by the recently emerged β-coronavirus SARS-CoV-2. SARS-CoV-2 has had a catastrophic impact, resulting in nearly 7 million fatalities worldwide to date. The innate immune system is the first line of defense against infections, including the detection and response to SARS-CoV-2. Here, we discuss the innate immune mechanisms that sense coronaviruses, with a focus on SARS-CoV-2 infection and how these protective responses can become detrimental in severe cases of COVID-19, contributing to cytokine storm, inflammation, long-COVID, and other complications. We also highlight the complex cross talk among cytokines and the cellular components of the innate immune system, which can aid in viral clearance but also contribute to inflammatory cell death, cytokine storm, and organ damage in severe COVID-19 pathogenesis. Furthermore, we discuss how SARS-CoV-2 evades key protective innate immune mechanisms to enhance its virulence and pathogenicity, as well as how innate immunity can be therapeutically targeted as part of the vaccination and treatment strategy. Overall, we highlight how a comprehensive understanding of innate immune mechanisms has been crucial in the fight against SARS-CoV-2 infections and the development of novel host-directed immunotherapeutic strategies for various diseases.

The choice of developing thymocytes to become CD8+ cytotoxic or CD4+ helper T cells has been intensely studied, but many of the underlying mechanisms remain to be elucidated. Recent multiomics approaches have provided much higher resolution analysis of gene expression in developing thymocytes than was previously achievable, thereby offering a fresh perspective on this question. Focusing on our recent studies using CITE-seq (cellular indexing of transcriptomes and epitopes) analyses of mouse thymocytes, we present a detailed timeline of RNA and protein expression changes during CD8 versus CD4 T cell differentiation. We also revisit our current understanding of the links between T cell receptor signaling and expression of the lineage-defining transcription factors ThPOK and RUNX3. Finally, we propose a sequential selection model to explain the tight linkage between MHC-I versus MHC-II recognition and T cell lineage choice. This model incorporates key aspects of previously proposed kinetic signaling, instructive, and stochastic/selection models.