Defining Genetic Variation in Widely Used Congenic and Backcrossed Mouse Models Reveals Varied Regulation of Genes Important for Immune Responses.

Genetic variation influences how the genome is interpreted in individuals and in mouse strains used to model immune responses. We developed approaches to utilize next-generation sequencing datasets to identify sequence variation in genes and enhancer elements in congenic and backcross mouse models. We defined genetic variation in the widely used B6-CD45.2 and B6.SJL-CD45.1 congenic model, identifying substantial differences in SJL genetic content retained in B6.SJL-CD45.1 strains on the basis of the vendor source of the mice. Genes encoding PD-1, CD62L, Bcl-2, cathepsin E, and Cxcr4 were within SJL genetic content in at least one vendor source of B6.SJL-CD45.1 mice. SJL genetic content affected enhancer elements, gene regulation, protein expression, and amino acid content in CD4+ T helper 1 cells, and mice infected with influenza showed reduced expression of Cxcr4 on B6.SJL-CD45.1 T follicular helper cells. These findings provide information on experimental variables and aid in creating approaches that account for genetic variables.

Immunity in adipose tissues: Cutting through the fat.

Well known functions of adipose tissue include energy storage, regulation of thermogenesis, and glucose homeostasis-each of which are associated with the metabolic functions of fat. However, adipose tissues also have important immune functions. In this issue of Immunological Reviews, we present a series of articles that highlight the immune functions of adipose tissue, including the roles of specialized adipose-resident immune cells and fat-associated lymphoid structures. Importantly, immune cell functions in adipose tissues are often linked to the metabolic functions of adipocytes and vice versa. These reciprocal interactions and how they influence both immune and metabolic functions will be discussed in each article. In the first article, Wang et al.,11 discuss adipose-associated macrophages and how obesity and metabolism impact their phenotype and function. Several articles in this issue discuss T cells as either contributors to, or regulators of, inflammatory responses in adipose tissues. Valentine and Nikolajczyk12 provide insights into the role of T cells in obesity-associated inflammation and their contribution to metabolic dysfunction, whereas an article from Kallies and Vasanthakumar13 and another from Elkins and Li14 describe adipose-associated Tregs and how they help prevent inflammation and maintain metabolic homeostasis. Articles from Okabe35 as well as from Daley and Benezech15 discuss the structure and function of fat-associated lymphoid clusters (FALCs) that are prevalent in some adipose tissues and support local immune responses to pathogens, gut-derived microbes and fat-associated antigens. Finally, an article from Meher and McNamara16 describes how innate-like B1 cells in adipose tissues regulate cardiometabolic disease. Importantly, these articles highlight the physical and functional attributes of adipose tissues that are different between mice and humans, the metabolic and immune differences between various adipose depots in the body and the differences in immune cells, adipose tissues and metabolic functions between the sexes. At the end of this preface, we highlight how these differences are critically important for our understanding of anti-tumor immunity to cancers that metastasize to a specific example of visceral adipose tissue, the omentum. Together, these articles identify some unanswered mechanistic questions that will be important to address for a better understanding of immunity in adipose tissues.

A spatial proteomic study of platinum refractory HGSOC implicates dual AKT and WNT activity linked to an immunosuppressive tumor microenvironment.

OBJECTIVE: Advanced-stage high-grade serous ovarian cancer (HGSOC) remains a deadly gynecologic malignancy with high rates of disease recurrence and limited, effective therapeutic options for patients. There is a significant need to better stratify HGSOC patients into platinum refractory (PRF) vs. sensitive (PS) cohorts at baseline to improve therapeutic responses and survival outcomes for PRF HGSOC. METHODS: We performed NanoString for GeoMx Digital Spatial Profile (G-DSP) multiplex protein analysis on PRF and PS tissue microarrays (TMAs) to study the bidirectional communication of cancer cells with immune cells in the tumor microenvironment (TME) of HGSOC. We demonstrate robust stratification of PRF and PS tumors at baseline using multiplex spatial proteomic biomarkers with implications for tailoring subsequent therapy. RESULTS: PS patients had elevated apoptotic and anti-tumor immune profiles, while PRF patients had dual AKT1 and WNT signaling with immunosuppressive profiles. We found that dual activity of AKT1 and WNT signaling supported the exclusion of immune cells, specifically tumor infiltrating lymphocytes (TILs), from the TME in PRF tumors, and this was not observed in PS tumors. The exclusion of immune cells from the TME of PRF tumors corresponded to abnormal endothelial cell structure in tumors with dual AKT1 and WNT signaling activity. CONCLUSIONS: We believe our findings provide improved understanding of tumor-immune crosstalk in HGSOC TME highlighting the importance of the relationship between AKT and WNT pathways, immune cell function, and platinum response in HGSOC.

Sequential modulation of the Wnt/ß-catenin signaling pathway enhances tumor-intrinsic MHC I expression and tumor clearance.

BACKGROUND: Progress in immunotherapy use for gynecologic malignancies is hampered by poor tumor antigenicity and weak T cell infiltration of the tumor microenvironment (TME). Wnt/ß-catenin pathway modulation demonstrated patient benefit in clinical trials as well as enhanced immune cell recruitment in preclinical studies. The purpose of this study was to characterize the pathways by which Wnt/ß-catenin modulation facilitates a more immunotherapy-favorable TME. METHODS: Human tumor samples and in vivo patient-derived xenograft and syngeneic murine models were administered Wnt/ß-catenin modulating agents DKN-01 and CGX-1321 individually or in sequence. Analytical methods included immunohistochemistry, flow cytometry, multiplex cytokine/chemokine array, and RNA sequencing. RESULTS: DKK1 blockade via DKN-01 increased HLA/MHC expression in human and murine tissues, correlating with heightened expression of known MHC I regulators: NFkB, IL-1, LPS, and IFNy. PORCN inhibition via CGX-1321 increased production of T cell chemoattractant CXCL10, providing a mechanism for observed increases in intra-tumoral T cells. Diverse leukocyte recruitment was noted with elevations in B cells and macrophages, with increased tumor expression of population-specific chemokines. Sequential DKK1 blockade and PORCN inhibition decreased tumor burden as evidenced by reduced omental weights. CONCLUSIONS: Wnt/ß-catenin pathway modulation increases MHC I expression and promotes tumor leukocytic infiltration, facilitating a pro-immune TME associated with decreased tumor burden. This intervention overcomes common tumor immune-evasion mechanisms and may render ovarian tumors susceptible to immunotherapy.

Immunological Functions of the Omentum.

The omentum is a visceral adipose tissue with unique immune functions. Although it is primarily an adipose tissue, the omentum also contains lymphoid aggregates, called milky spots (MSs), that contribute to peritoneal immunity by collecting antigens, particulates, and pathogens from the peritoneal cavity and, depending on the stimuli, promoting a variety of immune responses, including inflammation, tolerance, or even fibrosis. Reciprocal interactions between cells in the MS and adipocytes regulate their immune and metabolic functions. Importantly, the omentum collects metastasizing tumor cells and supports tumor growth by immunological and metabolic mechanisms. Here we summarize our current knowledge about the development, organization, and function of the omentum in peritoneal immunity.

The expression of MHC class II molecules on murine breast tumors delays T-cell exhaustion, expands the T-cell repertoire, and slows tumor growth.

The expression of MHC class II molecules (MHCII) on tumor cells correlates with survival and responsiveness to immunotherapy. However, the mechanisms underlying these observations are poorly defined. Using a murine breast tumor line, we showed that MHCII-expressing tumors grew more slowly than controls and recruited more functional CD4+ and CD8+ T cells. In addition, MHCII-expressing tumors contained more TCR clonotypes expanded to a larger degree than control tumors. Functional CD8+ T cells in tumors depended on CD4+ T cells. However, both CD4+ and CD8+ T cells eventually became exhausted, even in MHCII-expressing tumors. Treatment with anti-CTLA4, but not anti-PD-1 or anti-TIM-3, promoted complete eradication of MHCII-expressing tumors. These results suggest tumor cell expression of MHCII facilitates the local activation of CD4+ T cells, indirectly helps the activation and expansion of CD8+ T cells, and, in combination with the appropriate checkpoint inhibitor, promotes tumor regression.

The antitumor effects of entinostat in ovarian cancer require adaptive immunity.

BACKGROUND: Ovarian cancer is poorly immunogenic; however, increased major histocompatibility complex class II (MHCII) expression correlates with improved immune response and prolonged survival in patients with ovarian cancer. The authors previously demonstrated that the histone deacetylase inhibitor entinostat increases MHCII expression on ovarian cancer cells. In the current study, they evaluated whether entinostat treatment and resultant MHCII expression would enhance beneficial immune responses and impair tumor growth in mice with ovarian cancer. METHODS: C57BL/6 mice bearing intraperitoneal ID8 tumors were randomized to receive entinostat 20 mg/kg daily versus control. Changes in messenger RNA (mRNA) expression of 46 genes important for antitumor immunity were evaluated using NanoString analysis, and multicolor flow cytometry was used to measure changes in protein expression and tumor-infiltrating immune cells. RESULTS: Entinostat treatment decreased the growth of both subcutaneously and omental ID8 tumors and prolonged survival in immunocompetent C57BL/6 mice. NanoString analysis revealed significant changes in mRNA expression in 21 of 46 genes, including increased expression of the MHCI pathway, the MHCII transactivator (CIITA), interferon γ, and granzyme B. C57BL/6 mice that received entinostat had increased MHCII expression on omental tumor cells and a higher frequency of tumor-infiltrating, CD8-positive T cells by flow cytometry. In immunocompromised mice, treatment with entinostat had no effect on tumor size and did not increase MHCII expression. CONCLUSIONS: In the current murine ovarian cancer model, entinostat treatment enhances beneficial immune responses. Moreover, these antitumor effects of entinostat are dependent on an intact immune system. Future studies combining entinostat with checkpoint inhibitors or other immunomodulatory agents may achieve more durable antitumor responses in patients with ovarian cancer.

Proteobacteria impair anti-tumor immunity in the omentum by consuming arginine.

Gut microbiota influence anti-tumor immunity, often by producing immune-modulating metabolites. However, microbes consume a variety of metabolites that may also impact host immune responses. We show that tumors grow unchecked in the omenta of microbe-replete mice due to immunosuppressive Tregs. By contrast, omental tumors in germ-free, neomycin-treated mice or mice colonized with altered Schaedler's flora (ASF) are spontaneously eliminated by CD8+ T cells. These mice lack Proteobacteria capable of arginine catabolism, causing increases in serum arginine that activate the mammalian target of the rapamycin (mTOR) pathway in Tregs to reduce their suppressive capacity. Transfer of the Proteobacteria, Escherichia coli (E. coli), but not a mutant unable to catabolize arginine, to ASF mice reduces arginine levels, restores Treg suppression, and prevents tumor clearance. Supplementary arginine similarly decreases Treg suppressive capacity, increases CD8+ T cell effectiveness, and reduces tumor burden. Thus, microbial consumption of arginine alters anti-tumor immunity, offering potential therapeutic strategies for tumors in visceral adipose tissue.

Activation of regulatory dendritic cells by Mertk coincides with a temporal wave of apoptosis in neonatal lungs.

Multiple mechanisms restrain inflammation in neonates, most likely to prevent tissue damage caused by overly robust immune responses against newly encountered pathogens. Here, we identify a population of pulmonary dendritic cells (DCs) that express intermediate levels of CD103 (CD103int) and appear in the lungs and lung-draining lymph nodes of mice between birth and 2 weeks of age. CD103int DCs express XCR1 and CD205 and require expression of the transcription factor BATF3 for development, suggesting that they belong to the cDC1 lineage. In addition, CD103int DCs express CCR7 constitutively and spontaneously migrate to the lung-draining lymph node, where they promote stromal cell maturation and lymph node expansion. CD103int DCs mature independently of microbial exposure and TRIF- or MyD88-dependent signaling and are transcriptionally related to efferocytic and tolerogenic DCs as well as mature, regulatory DCs. Correlating with this, CD103int DCs show limited ability to stimulate proliferation and IFN-γ production by CD8+ T cells. Moreover, CD103int DCs acquire apoptotic cells efficiently, in a process that is dependent on the expression of the TAM receptor, Mertk, which drives their homeostatic maturation. The appearance of CD103int DCs coincides with a temporal wave of apoptosis in developing lungs and explains, in part, dampened pulmonary immunity in neonatal mice. Together, these data suggest a mechanism by which DCs sense apoptotic cells at sites of noninflammatory tissue remodeling, such as tumors or the developing lungs, and limit local T cell responses.

Neonate antigen presenting cells within murine intestinal muscular layer.

The intestinal mucosa is exposed to a vast antigenic contact. Several antigen presenting cell (APCs) have been described within the gut associated lymphoid tissue (GALT) (Peyer's patches, lamina propria, mesenteric lymph nodes, muscular layer); however, this has been done almost exclusively in adult organisms. As there is no characterization of intestinal muscular layer's APCs during early neonate development we adapted the conventional technique used in adults, to the neonate intestine. We obtained the intestinal muscular layer from early neonates (days 0-3 upon birth) and from young mice (2 and 3 weeks after birth). A planar network of CD45(+), MHC-II(+), DEC-205(+) cells with irregular, some with prominent dendritic morphology was found at birth under basal physiological conditions, whereas Langerin(+) DCs appeared after two weeks. The variations seen in CD45(+), MHC-II(+) and DEC-205(+) cells along the early neonatal development, could be related to the new challenges by intestinal antigen exposure from the newborn diet (breast milk, solid food), and to important environmental changes (start walking, exploring the surroundings, etc). Our study reveals the presence of APCs in intestinal muscular layer at birth, and their subsequent changes in physiological, non-induced conditions, contributing basic information about these cells in the neonate intestinal immune system.

Circulating Tregs Accumulate in Omental Tumors and Acquire Adipose-Resident Features.

Tumors that metastasize in the peritoneal cavity typically end up in the omental adipose tissue, a particularly immune-suppressive environment that includes specialized adipose-resident regulatory T cells (Treg). Tregs rapidly accumulate in the omentum after tumor implantation and potently suppress antitumor immunity. However, it is unclear whether these Tregs are recruited from the circulation or derived from preexisting adipose-resident Tregs by clonal expansion. Here we show that Tregs in tumor-bearing omenta predominantly have thymus-derived characteristics. Moreover, naïve tumor antigen-specific CD4+ T cells fail to differentiate into Tregs in tumor-bearing omenta. In fact, Tregs derived from the pretumor repertoire are sufficient to suppress antitumor immunity and promote tumor growth. However, tumor implantation in the omentum does not promote Treg clonal expansion, but instead leads to increased clonal diversity. Parabiosis experiments show that despite tissue-resident (noncirculating) characteristics of omental Tregs in naïve mice, tumor implantation promotes a rapid influx of circulating Tregs, many of which come from the spleen. Finally, we show that newly recruited Tregs rapidly acquire characteristics of adipose-resident Tregs in tumor-bearing omenta. These data demonstrate that most Tregs in omental tumors are recruited from the circulation and adapt to their environment by altering their homing, transcriptional, and metabolic properties.

Rotavirus infection activates dendritic cells from Peyer's patches in adult mice.

This study used an in vivo mouse model to analyze the response of dendritic cells (DCs) in Peyer's patches (PPs) within the first 48 h of infection with the wild-type murine rotavirus EDIM (EDIM(wt)). After the infection, the absolute number of DCs was increased by 2-fold in the PPs without a modification of their relative percentage of the total cell number. Also, the DCs from PPs of infected mice showed a time-dependent migration to the subepithelial dome (SED) and an increase of the surface activation markers CD40, CD80, and CD86. This response was more evident at 48 h postinfection (p.i.) and depended on viral replication, since DCs from PPs of mice inoculated with UV-treated virus did not show this phenotype. As a result of the activation, the DCs showed an increase in the expression of mRNA for the proinflammatory cytokines interleukin-12/23p40 (IL-12/23p40), tumor necrosis factor alpha (TNF-alpha), and beta interferon (IFN-beta), as well as for the regulatory cytokine IL-10. These results suggest that, a short time after rotavirus infection, the DCs from PPs play a critical role in controlling the infection and, at the same time, avoiding an excessive inflammatory immune response.

Specialized immune responses in the peritoneal cavity and omentum.

The peritoneal cavity is a fluid filled space that holds most of the abdominal organs, including the omentum, a visceral adipose tissue that contains milky spots or clusters of leukocytes that are organized similar to those in conventional lymphoid tissues. A unique assortment of leukocytes patrol the peritoneal cavity and migrate in and out of the milky spots, where they encounter Ags or pathogens from the peritoneal fluid and respond accordingly. The principal role of leukocytes in the peritoneal cavity is to preserve tissue homeostasis and secure tissue repair. However, when peritoneal homeostasis is disturbed by inflammation, infection, obesity, or tumor metastasis, specialized fibroblastic stromal cells and mesothelial cells in the omentum regulate the recruitment of peritoneal leukocytes and steer their activation in unique ways. In this review, the types of cells that reside in the peritoneal cavity, the role of the omentum in their maintenance and activation, and how these processes function in response to pathogens and malignancy will be discussed.

Neutralization of TGFß Improves Tumor Immunity and Reduces Tumor Progression in Ovarian Carcinoma.

The immunosuppressive effects of TGFß promotes tumor progression and diminishes response to therapy. In this study, we used ID8-p53-/- tumors as a murine model of high-grade serous ovarian cancer. An mAb targeting all three TGFß ligands was used to neutralize TGFß. Ascites and omentum were collected and changes in T-cell response were measured using flow. Treatment with anti-TGFß therapy every other day following injection of tumor cells resulted in decreased ascites volume (4.1 mL vs. 0.7 mL; P < 0.001) and improved the CD8:Treg ratio (0.37 vs. 2.5; P = 0.02) compared with untreated mice. A single dose of therapy prior to tumor challenge resulted in a similar reduction of ascites volume (2.7 vs. 0.67 mL; P = 0.002) and increased CD8:Tregs ratio (0.36 vs. 1.49; P = 0.007), while also significantly reducing omental weight (114.9 mg vs. 93.4 mg; P = 0.017). Beginning treatment before inoculation with tumor cells and continuing for 6 weeks, we observe similar changes and prolonged overall survival (median 70 days vs. 57.5 days). TGFß neutralization results in favorable changes to the T-cell response within the tumor microenvironment, leading to decreased tumor progression in ovarian cancer. The utilization of anti-TGFß therapy may be an option for management in patients with ovarian cancer to improve clinical outcomes and warrants further investigation.

Single-Dose Intranasal Administration of AdCOVID Elicits Systemic and Mucosal Immunity against SARS-CoV-2 and Fully Protects Mice from Lethal Challenge.

The coronavirus disease 2019 (COVID-19) pandemic has highlighted the urgent need for effective prophylactic vaccination to prevent the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Intranasal vaccination is an attractive strategy to prevent COVID-19 as the nasal mucosa represents the first-line barrier to SARS-CoV-2 entry. The current intramuscular vaccines elicit systemic immunity but not necessarily high-level mucosal immunity. Here, we tested a single intranasal dose of our candidate adenovirus type 5-vectored vaccine encoding the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein (AdCOVID) in inbred, outbred, and transgenic mice. A single intranasal vaccination with AdCOVID elicited a strong and focused immune response against RBD through the induction of mucosal IgA in the respiratory tract, serum neutralizing antibodies, and CD4+ and CD8+ T cells with a Th1-like cytokine expression profile. A single AdCOVID dose resulted in immunity that was sustained for over six months. Moreover, a single intranasal dose completely protected K18-hACE2 mice from lethal SARS-CoV-2 challenge, preventing weight loss and mortality. These data show that AdCOVID promotes concomitant systemic and mucosal immunity and represents a promising vaccine candidate.

Inhibiting WNT Ligand Production for Improved Immune Recognition in the Ovarian Tumor Microenvironment.

In ovarian cancer, upregulation of the Wnt/ß-catenin pathway leads to chemoresistance and correlates with T cell exclusion from the tumor microenvironment (TME). Our objectives were to validate these findings in an independent cohort of ovarian cancer subjects and determine whether inhibiting the Wnt pathway in a syngeneic ovarian cancer murine model could create a more T-cell-inflamed TME, which would lead to decreased tumor growth and improved survival. We preformed RNA sequencing in a cohort of human high grade serous ovarian carcinoma subjects. We used CGX1321, an inhibitor to the porcupine (PORCN) enzyme that is necessary for secretion of WNT ligand, in mice with established ID8 tumors, a murine ovarian cancer cell line. In order to investigate the effect of decreased Wnt/ß-catenin pathway activity in the dendritic cells (DCs), we injected ID8 cells in mice that lacked ß-catenin specifically in DCs. Furthermore, to understand how much the effects of blocking the Wnt/ß-catenin pathway are dependent on CD8+ T cells, we injected ID8 cells into mice with CD8+ T cell depletion. We confirmed a negative correlation between Wnt activity and T cell signature in our cohort. Decreasing WNT ligand production resulted in increases in T cell, macrophage and dendritic cell functions, decreased tumor burden and improved survival. Reduced tumor growth was found in mice that lacked ß-catenin specifically in DCs. When CD8+ T cells were depleted, CGX1321 treatment did not have the same magnitude of effect on tumor growth. Our investigation confirmed an increase in Wnt activity correlated with a decreased T-cell-inflamed environment; a relationship that was further supported in our pre-clinical model that suggests inhibiting the Wnt/ß-catenin pathway was associated with decreased tumor growth and improved survival via a partial dependence on CD8+ T cells.

Single-dose intranasal administration of AdCOVID elicits systemic and mucosal immunity against SARS-CoV-2 in mice.

The coronavirus disease 2019 (COVID-19) pandemic has highlighted the urgent need for effective preventive vaccination to reduce burden and spread of severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2) in humans. Intranasal vaccination is an attractive strategy to prevent COVID-19 as the nasal mucosa represents the first-line barrier to SARS-CoV-2 entry before viral spread to the lung. Although SARS-CoV-2 vaccine development is rapidly progressing, the current intramuscular vaccines are designed to elicit systemic immunity without conferring mucosal immunity. Here, we show that AdCOVID, an intranasal adenovirus type 5 (Ad5)-vectored vaccine encoding the receptor binding domain (RBD) of the SARS-CoV-2 spike protein, elicits a strong and focused immune response against RBD through the induction of mucosal IgA, serum neutralizing antibodies and CD4+ and CD8+ T cells with a Th1-like cytokine expression profile. Therefore, AdCOVID, which promotes concomitant systemic and local mucosal immunity, represents a promising COVID-19 vaccine candidate.

Inhibition of the Wnt/ß-catenin pathway enhances antitumor immunity in ovarian cancer.

BACKGROUND: The Wnt/ß-catenin pathway is linked to tumorigenesis in a variety of tumors and promotes T cell exclusion and resistance to checkpoint inhibitors. We sought to determine whether a small molecule inhibitor of this pathway, WNT974, would impair tumor growth, affect gene expression patterns, and improve the immune response in human and murine ovarian cancer models. METHODS: Human ovarian cancer cells were treated with WNT974 in vitro. RNAseq libraries were constructed and differences in gene expression patterns between responders and nonresponders were compared to The Cancer Genome Atlas (TCGA). Mice with subcutaneous or intraperitoneal ID8 ovarian cancer tumors were treated with WNT974, paclitaxel, combination, or control. Tumor growth and survival were measured. Flow cytometry and ß-TCR repertoire analysis were used to determine the immune response. RESULTS: Gene expression profiling revealed distinct signatures in responders and nonresponders, which strongly correlated with T cell infiltration patterns in the TCGA analysis of ovarian cancer. WNT974 inhibited tumor growth, prevented ascites formation, and prolonged survival in mouse models. WNT974 increased the ratio of CD8+ T cells to T regulatory cells (Tregs) in tumors and enhanced the effector functions of infiltrating CD4+ and CD8+ T cells. Treatment also decreased the expression of inhibitory receptors on CD8+ T cells. Combining WNT974 with paclitaxel further reduced tumor growth, prolonged survival, and expanded the T cell repertoire. CONCLUSIONS: These findings suggest that inhibiting the Wnt/ß-catenin pathway may have a potent immunomodulatory effect in the treatment of ovarian cancer, particularly when combined with paclitaxel.

Mitochondrial calcium uniporter regulates PGC-1α expression to mediate metabolic reprogramming in pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with an increased mortality. Metabolic reprogramming has a critical role in multiple chronic diseases. Lung macrophages expressing the mitochondrial calcium uniporter (MCU) have a critical role in fibrotic repair, but the contribution of MCU in macrophage metabolism is not known. Here, we show that MCU regulates peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and metabolic reprogramming to fatty acid oxidation (FAO) in macrophages. MCU regulated PGC-1α expression by increasing the phosphorylation of ATF-2 by the p38 MAPK in a redox-dependent manner. The expression and activation of PGC-1α via the p38 MAPK was regulated by MCU-mediated mitochondrial calcium uptake, which is linked to increased mitochondrial ROS (mtROS) production. Mice harboring a conditional expression of dominant-negative MCU in macrophages had a marked reduction in mtROS and FAO and were protected from pulmonary fibrosis. Moreover, IPF lung macrophages had evidence of increased MCU and mitochondrial calcium, increased phosphorylation of ATF2 and p38, as well as increased expression of PGC-1α. These observations suggest that macrophage MCU-mediated metabolic reprogramming contributes to fibrotic repair after lung injury.

Tertiary Lymphoid Structures Among the World of Noncanonical Ectopic Lymphoid Organizations.

Tertiary lymphoid structures (TLOs), also known as ectopic lymphoid structures, are associated with chronic infections and inflammatory diseases. Despite their association with pathology, these structures are actually a normal, albeit transient, component of the immune system and facilitate local immune responses that are meant to mitigate inflammation and resolve infection. Many of the mechanisms controlling the formation and function of tertiary lymphoid structures have been identified, in part by experimentally triggering their formation using defined stimuli under controlled conditions. Here, we introduce the experimental and pathological conditions in which tertiary lymphoid tissues are formed, describe the mechanisms linked to their formation, and discuss their functions in the context of both infection and inflammation.