Group 3 innate lymphocytes make a distinct contribution to type 17 immunity in bladder defence

ILC2-derived CGRP triggers acute inflammation and nociceptive responses in bacterial cystitis

Calcitonin gene-related peptide (CGRP), a neuropeptide involved in nociceptor neuronal function, plays a critical role in mediating neuroinflammation and pain. In this study, we find that bladder group 2 innate lymphoid cells (ILC2s) function as primary producers of CGRP in the early phase of bacterial cystitis, contributing to increased inflammation, altered voiding behavior, and heightened pelvic allodynia. Furthermore, we demonstrate that interleukin (IL)-33, a cytokine secreted by urothelial cells, upregulates CGRP production by ILC2s in the bladder during uropathogenic Escherichia coli (UPEC) infection. Moreover, our research reveals that monocytes expressing high levels of receptor activity-modifying protein 1 (RAMP1), a CGRP receptor, mediate the pro-inflammatory effects of CGRP-producing ILC2s. In summary, our results underscore the significance of the immune cell-derived neuropeptides in the pathology of UPEC infection, suggesting a promising therapeutic approach targeting the IL-33-ILC2-CGRP axis for managing lower urinary tract symptoms in bacterial cystitis.

Neutrophil extracellular traps protect the kidney from ascending infection and are required for a positive leukocyte dipstick test

Lower urinary tract infection (UTI) is common but only rarely complicated by pyelonephritis. However, the mechanisms preventing extension to the kidney are unclear. Here, we identified neutrophil extracellular traps (NETs) in healthy human urine that provide an antibacterial defense strategy within the urinary tract. In both in vivo murine models of UTI where uropathogenic E. coli are inoculated into the bladder and ex vivo human urine models, NETs interacted with uromodulin to form large webs that entrapped the bacteria. Peptidyl arginine deiminase 4 (PADI4) inhibition in mice blocked NETosis and resulted in progression of cystitis into pyelonephritis, suggesting that NETosis of urinary neutrophils acts to prevent bacterial ascent into the kidney. Analysis of UK Biobank data revealed that genetic variants in PADI4 that associated with increased risk of rheumatoid arthritis in multiple genome-wide association studies were consistently associated with reduced susceptibility to UTI. Last, we showed that urine dipstick testing for leukocyte esterase was negative in the presence of intact blood neutrophils but became positive when neutrophils were stimulated to NET, and this could be prevented by selective PADI4 inhibition, demonstrating that this test does not detect absolute neutrophil count, as has long been assumed, but specifically detects neutrophils that have undergone NETosis. These findings highlight the role of NETosis in preventing ascending infections in the urinary tract and improve our understanding of one of the most common clinical tests in medicine.

A Dynamic Interplay of Innate Immune Responses During Urinary Tract Infection

Urinary tract infections (UTIs) represent one of the most prevalent bacterial infections globally, manifesting in diverse clinical phenotypes with varying degrees of severity and complications. The mechanisms underlying UTIs are gradually being elucidated, leading to an enhanced understanding of the immune responses involved. Innate immune cells play a crucial defensive role against uropathogenic bacteria through various mechanisms. Despite their significant contributions to host defense, these cells often fail to achieve complete clearance of uropathogens, necessitating the frequent prescription of antibiotics for UTI patients. However, the persistence of infections and related pathological symptoms in the absence of innate immune cells in animal models underscore the importance of innate immunity in UTIs. Therefore, the host protective functions of innate immune cells, including neutrophils, macrophages, mast cells, NK cells, innate lymphoid cells, and γδ T cells, are delicately coordinated and timely regulated by a variety of cytokines to ensure successful pathogen clearance.

Innate Lymphoid Cells in Bladder Cancer: From Mechanisms of Action to Immune Therapies

Bladder tumors have a high mutational burden and tend to be responsive to immune therapies; however, response rates remain modest. To date, immunotherapy in bladder cancer has largely focused on enhancing T-cell immune responses in the bladder tumor microenvironment. It is anticipated that other immune cells, including innate lymphoid cells (ILC), which play an important role in bladder oncogenesis and tumor suppression, could be targeted to improve response to existing therapies. ILCs are classified into five groups: natural killer cells, ILC1s, ILC2s, ILC3s, and lymphoid tissue inducer cells. ILCs are pleiotropic and play dual and sometimes paradoxical roles in cancer development and progression. Here, a comprehensive discussion of the current knowledge and recent advancements in understanding the role of ILCs in bladder cancer is provided. We discuss the multifaceted roles that ILCs play in bladder immune surveillance, tumor protection, and immunopathology of bladder cancer. This review provides a rationale for targeting ILCs in bladder cancer, which is relevant for other solid tumors.

Type 2 innate lymphoid cells are not involved in mouse bladder tumor development

Therapies for bladder cancer patients are limited by side effects and failures, highlighting the need for novel targets to improve disease management. Given the emerging evidence highlighting the key role of innate lymphoid cell subsets, especially type 2 innate lymphoid cells (ILC2s), in shaping the tumor microenvironment and immune responses, we investigated the contribution of ILC2s in bladder tumor development. Using the orthotopic murine MB49 bladder tumor model, we found a strong enrichment of ILC2s in the bladder under steady-state conditions, comparable to that in the lung. However, as tumors grew, we observed an increase in ILC1s but no changes in ILC2s. Targeting ILC2s by blocking IL-4/IL-13 signaling pathways, IL-5, or IL-33 receptor, or using IL-33-deficient or ILC2-deficient mice, did not affect mice survival following bladder tumor implantation. Overall, these results suggest that ILC2s do not contribute significantly to bladder tumor development, yet further investigations are required to confirm these results in bladder cancer patients.

ILC3: a case of conflicted identity

Innate lymphoid cells type 3 (ILC3s) are the first line sentinels at the mucous tissues, where they contribute to the homeostatic immune response in a major way. Also, they have been increasingly appreciated as important modulators of chronic inflammatory and autoimmune responses, both locally and systemically. The proper identification of ILC3 is of utmost importance for meaningful studies on their role in immunity. Flow cytometry is the method of choice for the detection and characterization of ILC3. However, the analysis of ILC3-related papers shows inconsistency in ILC3 phenotypic definition, as different inclusion and exclusion markers are used for their identification. Here, we present these discrepancies in the phenotypic characterization of human and mouse ILC3s. We discuss the pros and cons of using various markers for ILC3 identification. Furthermore, we consider the possibilities for the efficient isolation and propagation of ILC3 from different organs and tissues for in-vitro and in-vivo studies. This paper calls upon uniformity in ILC3 definition, isolation, and propagation for the increased possibility of confluent interpretation of ILC3's role in immunity.

Immune defenses in the urinary tract

Recent advances in preclinical modeling of urinary tract infections (UTIs) have enabled the identification of key facets of the host response that influence pathogen clearance and tissue damage. Here, we review new insights into the functions of neutrophils, macrophages, and antimicrobial peptides in innate control of uropathogens and in mammalian infection-related tissue injury and repair. We also discuss novel functions for renal epithelial cells in innate antimicrobial defense. In addition, epigenetic modifications during bacterial cystitis have been implicated in bladder remodeling, conveying susceptibility to recurrent UTI. In total, contemporary work in this arena has better defined host processes that shape UTI susceptibility and severity and might inform the development of novel preventive and therapeutic approaches for acute and recurrent UTI.

CD90 is not constitutively expressed in functional innate lymphoid cells

Huge progress has been made in understanding the biology of innate lymphoid cells (ILC) by adopting several well-known concepts in T cell biology. As such, flow cytometry gating strategies and markers, such as CD90, have been applied to indentify ILC. Here, we report that most non-NK intestinal ILC have a high expression of CD90 as expected, but surprisingly a sub-population of cells exhibit low or even no expression of this marker. CD90-negative and CD90-low CD127+ ILC were present amongst all ILC subsets in the gut. The frequency of CD90-negative and CD90-low CD127+ ILC was dependent on stimulatory cues in vitro and enhanced by dysbiosis in vivo. CD90-negative and CD90-low CD127+ ILC were a potential source of IL-13, IFNγ and IL-17A at steady state and upon dysbiosis- and dextran sulphate sodium-elicited colitis. Hence, this study reveals that, contrary to expectations, CD90 is not constitutively expressed by functional ILC in the gut.

Effects of aging on urinary tract epithelial homeostasis and immunity

A global increase in older individuals creates an increasing demand to understand numerous healthcare challenges related to aging. This population is subject to changes in tissue physiology and the immune response network. Older individuals are particularly susceptible to infectious diseases, with one of the most common being urinary tract infections (UTIs). Postmenopausal and older women have the highest risk of recurrent UTIs (rUTIs); however, why rUTIs become more frequent after menopause and during old age is incompletely understood. This increased susceptibility and severity among older individuals may involve functional changes to the immune system with age. Aging also has substantial effects on the epithelium and the immune system that led to impaired protection against pathogens, yet heightened and prolonged inflammation. How the immune system and its responses to infection changes within the bladder mucosa during aging has largely remained poorly understood. In this review, we highlight our understanding of bladder innate and adaptive immunity and the impact of aging and hormones and hormone therapy on bladder epithelial homeostasis and immunity. In particular, we elaborate on how the cellular and molecular immune landscape within the bladder can be altered during aging as aged mice develop bladder tertiary lymphoid tissues (bTLT), which are absent in young mice leading to profound age-associated change to the immune landscape in bladders that might drive the significant increase in UTI susceptibility. Knowledge of host factors that prevent or promote infection can lead to targeted treatment and prevention regimens. This review also identifies unique host factors to consider in the older, female host for improving rUTI treatment and prevention by dissecting the age-associated alteration of the bladder mucosal immune system.