Tertiary Lymphoid Tissue Formation Research Articles

Pharmacological Management of IgG4-Related Disease: From Traditional to Mechanism-Based Targeted Therapies.

IgG4-related disease (IgG4-RD) is an immune-mediated disorder characterized by organ enlargement and dysfunction. The formation of tertiary lymphoid tissues (TLTs) in affected organs is crucial for understanding IgG4-RD, as T follicular helper (Tfh) 2 cells within TLTs drive IgG4+B cell differentiation, contributing to mass formation. Key cytokines IL-4 and IL-10, produced by Tfh2 cells, are essential for this process. Additionally, cytotoxic T cells and M2 macrophages significantly contribute to inflammation and fibrosis in the lesions. These insights into IgG4-RD have led to the development of innovative targeted therapies. While glucocorticoids are effective in many cases, they often cause disease flares during tapering and rarely result in long-term, treatment-free remissions. Long-term glucocorticoid use poses significant challenges owing to potential side effects, particularly in older patients who may already have complications such as diabetes and atherosclerotic diseases. In contrast, targeted therapies offer a promising alternative, potentially providing more effective disease control with fewer side effects. Current research is exploring several exciting approaches, including B-cell depletion, targeted immunomodulation of B cells, Bruton's tyrosine kinase inhibition, disruption of co-stimulation pathways, targeting the SLAMF7 cytokine or its receptor blockade (BAFF, IL-4, or IL-6), and JAK-STAT signaling pathway inhibition. These emerging strategies hold the promise of improving patient outcomes and advancing the management of IgG4-RD.

IgG4-related Disease: Recent Topics on Immunological Aspects of This Disorder and Their Application in New Treatment Strategies

IgG4-related disease (IgG4-RD) is a systemic and chronic inflammatory disorder that can affect every part of the body. The formation of tertiary lymphoid tissues (TLT) in the affected organs may be a key phenomenon in understanding the pathogenesis of this disease because T follicular helper (Tfh) 2 cells play an important role in IgG4 class switching within TLT in the affected organs or tissues. TLT formation leads to the formation of masses or swelling of the affected organs. Interleukin (IL)-4 and IL-10 are critical cytokines for IgG4-class switching and are produced in TLT. Other factors, such as CD4-positive (CD4+) cytotoxic T cells, M2 macrophages, and LAG3+ Tfh cells, have been identified as disease-specific contributors to lesion formation. In this review, I describe the current knowledge necessary to understand the pathogenesis of this disease and recent developments in treatment strategies beyond B-cell depletion therapy.

Involvement of Intestinal Epithelium Aryl Hydrocarbon Receptor Expression and 3, 3'-Diindolylmethane in Colonic Tertiary Lymphoid Tissue Formation.

Tertiary lymphoid tissues (TLTs) are adaptive immune structures that develop during chronic inflammation and may worsen or lessen disease outcomes in a context-specific manner. Immune cell activity governing TLT formation in the intestines is dependent on immune cell aryl hydrocarbon receptor (AhR) activation. Homeostatic immune cell activity in the intestines is further dependent on ligand activation of AhR in intestinal epithelial cells (IECs), yet whether AhR activation and signaling in IECs influences the formation of TLTs in the presence of dietary AhR ligands is not known. To this end, we used IEC-specific AhR deletion coupled with a mouse model of dextran sodium sulfate (DSS)-induced colitis to understand how dietary AhR ligand 3, 3'-diindolylmethane (DIM) influenced TLT formation. DIM consumption increased the size of TLTs and decreased T-cell aggregation to TLT sites in an IEC-specific manner. In DSS-exposed female mice, DIM consumption increased the expression of genes implicated in TLT formation (Interleukin-22, Il-22; CXC motif chemokine ligand 13, CXCL13) in an IEC AhR-specific manner. Conversely, in female mice without DSS exposure, DIM significantly reduced the expression of Il-22 or CXCL13 in iAhRKO mice, but this effect was not observed in WT animals. Our findings suggest that DIM affects the immunological landscape of TLT formation during DSS-induced colitis in a manner contingent on AhR expression in IECs and biological sex. Further investigations into specific immune cell activity, IEC-specific AhR signaling pathways, and dietary AhR ligand-mediated effects on TLT formation are warranted.

The atypical chemokine receptor 2 reduces T cell expansion and tertiary lymphoid tissue but does not limit autoimmune organ injury in lupus-prone B6lpr mice.

The atypical chemokine receptor 2 (ACKR2) is a chemokine scavenger receptor, which limits inflammation and organ damage in several experimental disease models including kidney diseases. However, potential roles of ACKR2 in reducing inflammation and tissue injury in autoimmune disorders like systemic lupus erythematosus (SLE) and lupus nephritis are unknown, as well as its effects on systemic autoimmunity. To characterize functional roles of ACKR2 in SLE, genetic Ackr2 deficiency was introduced into lupus-prone C57BL/6lpr (Ackr2-/- B6lpr) mice. Upon inflammatory stimulation in vitro, secreted chemokine levels increased in Ackr2 deficient tubulointerstitial tissue but not glomeruli. Moreover, Ackr2 expression was induced in kidneys and lungs of female C57BL/6lpr mice developing SLE. However, female Ackr2-/- B6lpr mice at 28 weeks of age showed similar renal functional parameters as wildtype (WT)-B6lpr mice. Consistently, assessment of activity and chronicity indices for lupus nephritis revealed comparable renal injury. Interestingly, Ackr2-/- B6lpr mice showed significantly increased renal infiltrates of CD3+ T and B cells, but not neutrophils, macrophages or dendritic cells, with T cells predominantly accumulating in the tubulointerstitial compartment of Ackr2-/- B6lpr mice. In addition, histology demonstrated significantly increased peribronchial lung infiltrates of CD3+ T cells in Ackr2-/- B6lpr mice. Despite this, protein levels of pro-inflammatory chemokines and mRNA expression of inflammatory mediators were not different in kidneys and lungs of WT- and Ackr2-/- B6lpr mice. This data suggests compensatory mechanisms for sufficient chemokine clearance in Ackr2-deficient B6lpr mice in vivo. Analysis of systemic autoimmune responses revealed comparable levels of circulating lupus-associated autoantibodies and glomerular immunoglobulin deposition in the two genotypes. Interestingly, similar to kidney and lung CD4+ T cell numbers and activation were significantly increased in spleens of Ackr2-deficient B6lpr mice. In lymph nodes of Ackr2-/- B6lpr mice abundance of activated dendritic cells decreased, but CD4+ T cell numbers were comparable to WT. Moreover, increased plasma levels of CCL2 were present in Ackr2-/- B6lpr mice, which may facilitate T cell mobilization into spleens and peripheral organs. In summary, we show that ACKR2 prevents expansion of T cells and formation of tertiary lymphoid tissue, but is not essential to limit autoimmune tissue injury in lupus-prone B6lpr mice.

Single cell sequencing data identify distinct B cell and fibroblast populations in stricturing Crohn's disease.

Single cell RNA sequencing of human full thickness Crohn's disease (CD) small bowel resection specimens was used to identify potential therapeutic targets for stricturing (S) CD. Using an unbiased approach, 16 cell lineages were assigned within 14,539 sequenced cells from patient-matched SCD and non-stricturing (NSCD) preparations. SCD and NSCD contained identical cell types. Amongst immune cells, B cells and plasma cells were selectively increased in SCD samples. B cell subsets suggested formation of tertiary lymphoid tissue in SCD and compared with NSCD there was an increase in IgG, and a decrease in IgA plasma cells, consistent with their potential role in CD fibrosis. Two Lumican-positive fibroblast subtypes were identified and subclassified based on expression of selectively enriched genes as fibroblast clusters (C) 12 and C9. Cells within these clusters expressed the profibrotic genes Decorin (C12) and JUN (C9). C9 cells expressed ACTA2; ECM genes COL4A1, COL4A2, COL15A1, COL6A3, COL18A1 and ADAMDEC1; LAMB1 and GREM1. GO and KEGG Biological terms showed extracellular matrix and stricture organization associated with C12 and C9, and regulation of WNT pathway genes with C9. Trajectory and differential gene analysis of C12 and C9 identified four sub-clusters. Intra sub-cluster gene analysis detected 13 co-regulated gene modules that aligned along predicted pseudotime trajectories. CXCL14 and ADAMDEC1 were key markers in module 1. Our findings support further investigation of fibroblast heterogeneity and interactions with local and circulating immune cells at earlier time points in fibrosis progression. Breaking these interactions by targeting one or other population may improve therapeutic management for SCD.

Aryl hydrocarbon receptor activity in intestinal epithelial cells in the formation of colonic tertiary lymphoid tissues.

After birth, the development of secondary lymphoid tissues (SLTs) in the colon is dependent on the expression of the aryl hydrocarbon receptor (AhR) in immune cells as a response to the availability of AhR ligands. However, little is known about how AhR activity from intestinal epithelial cells (IECs) may influence the development of tertiary lymphoid tissues (TLTs). As organized structures that develop at sites of inflammation or infection during adulthood, TLTs serve as localized centers of adaptive immune responses, and their presence has been associated with the resolution of inflammation and tumorigenesis in the colon. Here, we investigated the effect of the conditional loss of AhR activity in IECs in the formation and immune cell composition of TLTs in a model of acute inflammation. In females, loss of AhR activity in IECs reduced the formation of TLTs without significantly changing disease outcomes or immune cell composition within TLTs. In males lacking AhR expression in IECs, increased disease activity index, lower expression of functional-IEC genes, increased number of TLTs, increased T-cell density, and lower B- to T-cell ratio were observed. These findings may represent an unfavorable prognosis when exposed to dextran sodium sulfate (DSS)-induced epithelial damage compared with females. Sex and loss of IEC AhR also resulted in changes in microbial populations in the gut. Collectively, these data suggest that the formation of TLTs in the colon is influenced by sex and AhR expression in IECs.NEW & NOTEWORTHY This is the first research of its kind to demonstrate a clear connection between biological sex and the development of tertiary lymphoid tissues (TLT) in the colon. In addition, the research finds that in a preclinical model of inflammatory bowel disease, the expression of the aryl hydrocarbon receptor (AhR) influences the development of these structures in a sex-specific manner.

Young Plasma Attenuated Chronic Kidney Disease Progression after Acute Kidney Injury by Inhibiting Inflammation in Mice.

In the aged patients suffering from acute kidney injury, the risk for progression to chronic kidney disease and mortality is high. Aging accompanied by glomerulosclerosis, interstitial inflammation, and fibrosis might be one of the underlying mechanisms for vulnerability. In addition to sustained activation of the renin-angiotensin system, persistent chronic inflammation with tertiary lymphoid tissue formation is more common and is associated with disease progression in the aged kidney after acute injury. Based on recent laboratory evidence that young blood can rejuvenate the brain, muscle, and heart, we were intrigued by the possible protective effect of young plasma on acute kidney injury in aged mice. Here, we demonstrated that young plasma from 2-month-old mice could attenuate chronic kidney disease progression in 15-month-old mice subjected to acute kidney injury induced by ischemia-reperfusion. In the aged mice after acute kidney injury, young plasma administration decreased tubulointerstitial injury, fibrosis, and tertiary lymphoid tissue formation in kidneys assessed on day 28 after acute injury despite no significant beneficial effect on injury severity and survival. Mechanistically, young plasma inhibited angiotensin II-activated chemokines in pericytes that were responsible for tertiary lymphoid tissue formation. In summary, our data provide evidence that young plasma attenuates the transition from acute kidney injury to chronic kidney disease in aged mice. The therapeutic potential of young plasma infusion or exchange in the aged patients suffering acute kidney injury needs to be addressed in clinical trials.

Glutathione Synthesis Contributes to the Formation of Tertiary Lymphoid Tissues in the Kidney

Glutathione Synthesis Contributes to the Formation of Tertiary Lymphoid Tissues in the Kidney

The mutation PTPN6Ala455Thrcausing pulmonary emphysema affects B cell populations and causes spontaneous pulmonary tertiary lymphoid tissue formation

Abstract Rationale: A new mutation causing severe pulmonary emphysema was recently discovered in a French-Canadian family. The mutation is located in the PTPN6 gene (PTPN6 Ala455Thr) leading to a reduction in the activity of SHP-1, a phosphatase that regulates pathways associated to B cells. We aimed to characterize B cell abnormalities associated with aging in both humans and mice carrying this mutation. Methods: Circulating B cell populations in humans carrying the PTPN6Ala455Thrmutation were analyzed by flow cytometry and immunoglobulin levels were measured in serum. In mice carrying the same mutation (Ptpn6Ala457Thr) aged up to 12 months, B cell populations were analyzed by flow cytometry and lung tissue histology performed. Mice were immunized with the T cell-independent antigen and NP-specific antibodies were measured in plasma. Results: Human carriers of the PTPN6Ala455Thrmutation had reduced IgG1 and IgG4, and increased IgG3 levels as well as a lower ratio of naive B cells/ isotype switched memory B cells compared to controls. Aging Ptpn6Ala457Thrmice developed spontaneous pulmonary tertiary lymphoid tissues and exhibited higher proportion of B-1 cells, age-associated B cells and germinal center B cells along with lower B-2 cells in the lung and spleen. Ptpn6Ala457Thrmice had lower levels of NP-specific IgG1 antibodies compared to the wild-type group. Conclusion: SHP-1 appears to affect aging of B cells as the PTPN6Ala455Thrmutation leads to changes in B cell populations associated with age, tertiary lymphoid tissue formation and an alteration of immunoglobulin levels. The link between B cell abnormalities, aging and emphysema requires further investigation. Funding:CIHR, FRQS CIHR, FRQS

Abstract 3443: Aryl hydrocarbon receptor and its ligands influence the formation of colonic tertiary lymphoid tissues

Abstract Background: In the large intestine, tertiary lymphoid tissues (TLTs) serve as localized centers of adaptive immune responses. These structures often form in response to inflammation and infection during adulthood. However, more recently TLTs have become a focal point of colon caner development and progression as their presence is often associated with positive clinical outcomes. Interestingly, several studies have demonstrated that the aryl hydrocarbon receptor (AhR) influences the development of secondary lymphoid tissues, but minimal studies have focused on its role in TLT formation. The purpose of the presented studies was to test the hypothesis that activation of AhR in intestinal epithelial cells (IECs) induces the formation of TLTs in the colon. Methods: Wild type (WT) and IEC-specific AhR knockout (CDX2PCreT2 x AhRf/f- iAhRKO) mice were used in several different experimental models. In the first study, azoxymethane (AOM) was used to induce precancerous lesions in the colon and TLT formation was evaluated in the presence and absence of AhR. Then, experiments were conducted to determine the necessity of AhR expression in IECs to influence the formation of TLTs following induction of acute inflammation induced by Dextran sodium sulfate (DSS) exposure. Finally, the ability of known, naturally occurring and microbial-derived AhR ligands (indole-3-aldehyde (I3A), 3,3ʹ-diindolylmethane (DIM), and indole-3-acetic acid (IAA)) were tested for their ability to induce TLT formation in the colon. Intestinal permeability (FITC-Dextran), expression of IEC-associated genes (real-time qPCR), and TLT formation/composition (H&E staining/Immunofluorescence) were evaluated. Results: Results from the first study demonstrated that IEC-specific AhR KO mice exposed to AOM developed significantly fewer TLTs when compared to WT controls, while expression of Il-22 and other chemokines involved in TLT formation were also significantly downregulated. In the acute inflammation study, sex specific results were found. In females, loss of AhR activity in IECs reduced the formation of TLTs without significant changes in immune cell composition within their TLTs. Conversely, in males, loss of AhR lowered expression of functional-IEC genes (Ocln, Il-22), increased number of TLTs, increased T-cell density, and lower B: T cell ratio. Finally, in the other experiments, I3A induced TLT formation and DIM promoted intestinal barrier integrity through the upregulation of various tight junction genes and genes involved in the signaling associated with TLT formation. Evaluation of IAA which is a microbial-derived, AhR ligand is ongoing. Conclusion: These data indicate that AhR plays a distinct role in the formation of TLTs in the colon and these effects are likely ligand specific and may have a significant effect on colon tumor formation. Citation Format: Kimberly F. Allred, Erika L. Garcia-Villatoro, Jennifer DeLuca, Victoria Tepe, Zachary Bomstein, Arinzechukwu Ufondu, Stephen H. Safe, Robert S. Chapkin, Arul Jayaraman, Clinton D. Allred. Aryl hydrocarbon receptor and its ligands influence the formation of colonic tertiary lymphoid tissues [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3443.

S-41-2: ROLE OF TERTIARY LYMPHOID TISSUES IN KIDNEY INFLAMMATION

Kidneys are vulnerable organs, and often fail to repair. In particular, renal damage is prolonged and severe in the elderly, but the mechanism behind this was unknown. Recently, we identified a unique microenvironment orchestrating kidney injury and inflammation. Tertiary lymphoid tissues (TLTs), which mainly consist of lymphocytes and fibroblasts, are formed in the chronic phase after injury in aged kidneys, contributing to prolonged inflammation and delayed regeneration. Resident fibroblasts in the kidney play critical roles in the formation of TLTs by acquiring the abilities to produce retinoic acid and homeostatic chemokines, and to support B cell area formation. Notably, therapeutic strategy targeting TLTs attenuates tubular injury and fibrosis in mouse models. Furthermore, TLTs are found in human kidneys, and the presence of advanced-stage TLTs correlates with the severity of kidney injury and inflammation. Specifically, TLTs are commonly found in protocol biopsies of transplanted kidneys, and advanced-stage TLTs are associated with progressive graft dysfunction. Recently, we identifed TNF superfamily CD153-CD30 signaling between two unique age-dependent lymphocyte subpopulations, senescence-associated T (SAT) cells and age-associated B cells (ABCs), as a driver for TLT expansion, and demonstrated that CD153 or CD30 deficiency resulted in attenuated TLT formation with improved inflammation, fibrosis and renal function. Understanding the mechanism of TLT formation may provide clues for the development of therapeutic agents for slowing kidney disease progression.

Supraphysiologic Vaginal Estrogen Therapy in Aged Mice Mitigates Age-Associated Bladder Inflammatory Response to Urinary Tract Infections.

Bladder diseases characterized by chronic inflammation are highly prevalent in older women, as are recurrent urinary tract infections (rUTIs). Recurrent urinary tract infections lead to chronic inflammation of the bladder mucosa and cause lower urinary tract symptoms that persist even after the infection is cleared. Vaginal estrogen therapy (VET) has long been used for the treatment of rUTIs; however, its mechanism of action remains unclear. The objective of this study was to examine the mechanism(s) by which VET affects bladder inflammation and response to rUTIs. Here, we induced surgical menopause in aged (18 months old) mice followed by VET. Mice were then infected with uropathogenic Escherichia coli , and course of infection was investigated. Inflammatory cytokine response was assessed before and during infection using enzyme-linked immunosorbent assay. RNA sequencing analysis was used to compare the inflammatory status of the young versus aged bladder and principal changes confirmed via quantitative reverse transcriptase-polymerase chain reaction to determine the effects of VET on bladder inflammation. Impact on age-associated bladder tertiary lymphoid tissue formation was evaluated histologically. In the ovariectomized aged model, VET not only mitigated uterine atrophy but was also associated with reduced rUTIs, number of bacterial reservoirs, dampened immune response, and promotion of terminal differentiation of urothelial cells. Bladder tertiary lymphoid tissue lesions were also reduced with VET, with an associated decrease in signals important for bladder tertiary lymphoid tissue formation. Finally, we determined that VET reverses age-associated upregulation of inflammatory genes and pathways. Our data suggest that VET is effective by reducing age-associated hyperinflammatory conditions in bladder mucosa and in enhancing the host response to infection.

The mutation PTPN6Ala455Thr causing pulmonary emphysema affects B lymphocyte populations and causes spontaneous pulmonary tertiary lymphoid tissue formation

Abstract Background A new mutation responsible for causing severe and early pulmonary emphysema was recently discovered in a French-Canadian family. The mutation is located in the PTPN6 gene (PTPN6Ala455Thr) leading to a reduction in the activity of SHP-1, a phosphatase that regulates numerous pathways including B cell differentiation and activation. Here, we aimed to characterize B cell abnormalities in both humans and mice carrying this mutation. Methods Circulating B cell populations in humans carrying the PTPN6Ala455Thr mutation were analyzed by flow cytometry and immunoglobulin levels were measured in serum. In mice carrying the same mutation (Ptpn6Ala457Thr) aged up to 12 months, B cell populations were analyzed by flow cytometry and lung tissue histology performed. Mice were immunized with the T cell-independent antigen NP-Ficoll and plasma was collected to assess NP-specific antibodies. Results Human carriers of the PTPN6Ala455Thr mutation had reduced IgG1 and IgG4, and increased IgG3 levels as well as high circulating immature/mature B cell ratio compared to controls. Aging Ptpn6Ala457Thr mice developed spontaneous pulmonary tertiary lymphoid tissues and exhibited higher B-1 cells and lower B-2 cells proportions in the lung and spleen. Ptpn6Ala457Thr mice had lower levels of NP-specific IgG1 antibodies compared to the wild-type group, but normal IgG3 in response to NP-Ficoll immunization. Conclusion SHP-1 appears to be important to B cell development and functions, as the PTPN6Ala455Thr mutation seems to cause a form of subclinical immunodeficiency that affects B cell populations and immunoglobulin levels. The link between B cell abnormalities and development of pulmonary emphysema requires further investigation. Supported by grants from Canadian Institutes of Health and Research and Fonds de Recherche du Québec- Santé

S01.1: Age‐ sex‐, and TNFα‐dependent but microbiota‐independent tertiary lymphoid tissue formation in the urinary tract

S01.1: Age‐ sex‐, and TNFα‐dependent but microbiota‐independent tertiary lymphoid tissue formation in the urinary tract

Tertiary lymphoid tissue in early\u2010stage IgG4-related tubulointerstitial nephritis incidentally detected with a tumor lesion of the ureteropelvic junction: a case report

BackgroundIgG4-related kidney disease causes renal impairment of unknown pathogenesis that may progress to kidney failure. Although ectopic germinal centers contribute to the pathogenesis of the head and neck lesions of IgG4-related disease, the presence of tertiary lymphoid tissue (TLT) containing germinal centers in IgG4-RKD has rarely been reported. Case presentationWe report a 72-year-old Japanese man who had IgG4-related tubulointerstitial nephritis (TIN) with TLT formation incidentally detected in a resected kidney with mass lesion of IgG4-related ureteritis in the ureteropelvic junction. During follow-up for past surgical resection of a bladder tumor, renal dysfunction developed and a ureter mass was found in the right ureteropelvic junction, which was treated by nephroureterectomy after chemotherapy. Pathology revealed no malignancy but abundant IgG4-positive cell infiltration, obliterative phlebitis and storiform fibrosis, confirming the diagnosis of IgG4-related ureteritis. In the resected right kidney, lymphoplasmacytes infiltrated the interstitium with focal distribution in the renal subcapsule and around medium vessels without storiform fibrosis, suggesting the very early stage of IgG4-TIN. Lymphocyte aggregates were also detected at these sites and consisted of B, T, and follicular dendritic cells, indicating TLT formation. IgG4-positive cells infiltrated around TLTs.ConclusionsOur case suggests that TLT formation is related with the development of IgG4-TIN and our analysis of distribution of TLT have possibility to elucidate IgG4-TIN pathophysiology.

Impact of Local Alloimmunity and Recipient Cells in Transplant Arteriosclerosis.

Transplant arteriosclerosis is the major limitation to long-term survival of solid organ transplantation. Although both immune and nonimmune cells have been suggested to contribute to this process, the complex cellular heterogeneity within the grafts, and the underlying mechanisms regulating the disease progression remain largely uncharacterized. We aimed to delineate the cellular heterogeneity within the allografts, and to explore possible mechanisms underlying this process. Here, we reported the transcriptional profiling of 11 868 cells in a mouse model of transplant arteriosclerosis by single-cell RNA sequencing. Unbiased clustering analyses identified 21 cell clusters at different stages of diseases, and focused analysis revealed several previously unknown subpopulations enriched in the allografts. Interestingly, we found evidence of the local formation of tertiary lymphoid tissues and suggested a possible local modulation of alloimmune responses within the grafts. Intercellular communication analyses uncovered a potential role of several ligands and receptors, including Ccl21a and Cxcr3, in regulating lymphatic endothelial cell-induced early chemotaxis and infiltration of immune cells. In vivo mouse experiments confirmed the therapeutic potential of CCL21 and CXCR3 neutralizing antibodies in transplant arteriosclerosis. Combinational use of genetic lineage tracing and single-cell techniques further indicate the infiltration of host-derived c-Kit+ stem cells as heterogeneous populations in the allografts. Finally, we compared the immune response between mouse allograft and atherosclerosis models in single-cell RNA-seq analysis. By analyzing susceptibility genes of disease traits, we also identified several cell clusters expressing genes associated with disease risk. Our study provides a transcriptional and cellular landscape of transplant arteriosclerosis, which could be fundamental to understanding the initiation and progression of this disease. CCL21/CXCR3 was also identified as important regulators of immune response and may serve as potential therapeutic targets in disease treatment.

Janus-Faced: Molecular Mechanisms and Versatile Nature of Renal Fibrosis.

Renal fibrosis is a major hallmark of CKD, regardless of the underlying etiology. In fibrosis development and progression, myofibroblasts play a pivotal role, producing extracellular matrix and interacting with various resident cells in the kidney. Over the past decade, the origin of myofibroblasts has been thoroughly investigated. Emerging evidence suggests that renal myofibroblasts originate from several cellular sources, including resident fibroblasts, pericytes, and bone marrow-derived cells. The contribution of resident fibroblasts is most crucial, and currently available data strongly suggest the importance of functional heterogeneity and plasticity of fibroblasts in kidney disease progression. Resident fibroblasts acquire distinct phenotypes based on their local microenvironment and exert multifactorial functions. For example, age-dependent alterations of renal fibroblasts make a significant contribution to the formation of tertiary lymphoid tissues, which promote local inflammation after injury in the aged kidney. In conjunction with fibrosis development, dysfunction of resident fibroblasts provokes unique pathologic conditions including renal anemia and peritubular capillary loss, both of which are major complications of CKD. Although renal fibrosis is considered detrimental in general, recent studies suggest it has beneficial roles, such as maintaining functional crosstalk with injured proximal tubular cells and supporting their regeneration. These findings provide novel insight into the mechanisms of renal fibrosis, which could be regarded as an adaptive process of kidney injury and repair. Precise understanding of the functional heterogeneity of resident fibroblasts and myofibroblasts has the potential to facilitate the development of novel therapeutics against kidney diseases. In this review, we describe the current perspective on the origin of myofibroblasts and fibroblast heterogeneity, with special emphasis on the dual aspects of renal fibrosis, both beneficial and detrimental, in CKD progression.

Single cell and tissue-transcriptomic analysis of murine bladders reveals age- and TNFα-dependent but microbiota-independent tertiary lymphoid tissue formation.

Aging has multifaceted effects on the immune system, but how aging affects tissue-specific immunity is not well-defined. Bladder diseases characterized by chronic inflammation are highly prevalent in older women, but mechanisms by which aging promotes these pathologies remain unknown. Tissue transcriptomics of unperturbed, young and aged bladders identified a highly altered immune landscape as a fundamental feature of the aging female bladder. Detailed mapping of immune cells using single cell RNA-sequencing revealed novel subsets of macrophages and dendritic cells and unique changes to the immune repertoire in the aged bladder. B and T cells are highly enriched in aged bladders and spontaneously form organized bladder tertiary lymphoid tissues (bTLTs). Naïve, activated, and germinal center B cells and IgA+ plasma cells are found within bTLT and associated with increased urinary IgA concentrations. bTLTs form with increasing age and their formation is dependent on TNFα. Microbiota are not required to form bTLT form, as aged germfree mice harbor them. Thus, bTLTs require age-dependent TNFα but are independent of the microbiota. Our results indicate that chronic, age-associated inflammation underlies a fundamental alteration to the bladder and establishes a resource for further investigation of the bladder immune system in homeostasis, aging, and disease.

Skin-Associated B Cells in Health and Inflammation.

Traditionally, the skin was believed to be devoid of B cells, and studies of the skin immune system have largely focused on other types of leukocytes. Exciting recent data show that B cells localize to the healthy skin of humans and other mammalian species with likely homeostatic functions in host defense, regulation of microbial communities, and wound healing. Distinct skin-associated B cell subsets drive or suppress cutaneous inflammatory responses with important clinical implications. Localized functions of skin-associated B cell subsets during inflammation comprise Ab production, interactions with skin T cells, tertiary lymphoid tissue formation, and production of proinflammatory cytokines but also include immunosuppression by providing IL-10. In this review, we delve into the intriguing new roles of skin-associated B cells in homeostasis and inflammation.

Immune cells and inflammation in AKI to CKD progression.

Acute kidney injury (AKI) is a common clinical state resulting from pathogenic conditions such as ischemic and toxic insults. The pathophysiology of AKI shares common pathogenic denominators including cell death/injury, inflammation, and fibrosis, regardless of the initiating insults. Recent clinical studies have shown that a single episode of AKI can lead to subsequent chronic kidney disease (CKD). Although the involvement of multiple types of cells in the pathophysiology of AKI is becoming increasingly clear, the precise mechanisms for this "AKI to CKD progression" are still unknown, and no drug has been shown to halt this progression. An increasing number of epidemiological studies have also revealed that the presence of aging greatly increases the risk of AKI to CKD progression, and chronic inflammation is increasingly recognized as an important determinant factor for this progression. In this review article, we first describe the current understanding of the pathophysiology of AKI to CKD progression based on multiple types of cells. In particular, we will highlight the recent findings in regard to the mechanisms for chronic inflammation after AKI. Subsequently, we will focus on the mechanisms responsible for the increased risk of AKI to CKD progression in the elderly. Finally, we highlight our recent finding of age-dependent tertiary lymphoid tissue formation and its roles in AKI to CKD progression and speculate on the potential therapeutic opportunities that come from targeting aberrant inflammation after AKI.