Lymphoid Tissue Inducer Research Articles

LTi-like type 3 innate lymphoid cells are associated with the transient induction of tertiary lymphoid structures in inflamed pulmonary tissue

Abstract Tertiary lymphoid structures (TLS) are ectopic lymphoid aggregates observed in inflamed tissues. Their presence in pulmonary tissue has been associated with good prognosis in patients with lung cancer. Although TLS formation shares common features with secondary lymphoid organogenesis, the mechanisms underlying this process are yet to be fully elucidated. Presence of ILC3 in the vicinity of tumor-associated TLS correlates with the density of lymphoid structures. We hypothesized that RORγt+ ILC3 play a major role in TLS induction in inflamed lungs, as do RORγt+ fetal lymphoid tissue inducer cells (LTi) during lymph node formation. We developed a murine model of pulmonary inflammation induced by LPS intranasal instillation that triggers TLS formation. ILC3 presence in lungs was observed with a specific flow cytometry antibody panel. Three RORgt+ILC3 subsets (NCR− CCR6−, NCR−CCR6+, NCR+CCR6−) were detected. In particular, NCR−CCR6+ LTi-like cells represented about 25% of CD117+CD127+ILC (ILC2/ILC3) and less than 0.04% among CD45+ cells. Analyses of ILC subsets at different time points following LPS instillation showed an increase in the number and % (up to 0.59%) of ILC3 among CD45+ cells, as well as an increase in the % of LTi-like ILC3 among CD45+ cells, that peaked around day 10 (from 0.02% up to 0.15%). Quantification of TLS by histochemistry showed that they are induced in lung tissue in an LPS dose-dependent manner. TLS density increases between days 3 and 10 and decreases thereafter. They were no longer detected at day 25, while LTi-like ILC3 % returned to baseline. Gene expression analysis and functional assays of sorted LTi-like ILC3 are essential to determine if these cells are key players in TLS induction. Supported by grants from La Ligue Nationale contre le cancer (TAHG21042) and Fondation ARC (R19232DD).

The Metabolic Basis of ILC Plasticity.

Innate Lymphoid Cells (ILCs) are the innate counterpart of adaptive lymphoid T cells. They are key players in the regulation of tissues homeostasis and early inflammatory host responses. ILCs are divided into three groups, and further subdivided into five subsets, that are characterised by distinct transcription factors, surface markers and their cytokine expression profiles. Group 1 ILCs, including natural killer (NK) cells and non-NK cell ILC1s, express T-bet and produce IFN-γ. Group 2 ILCs depend on GATA3 and produce IL-4, IL-5 and IL-13. Group 3 ILCs, composed of ILC3s and Lymphoid Tissue Inducer (LTi) cells, express RORγt and produce IL-17 and IL-22. Even though, the phenotype of each subset is well defined, environmental signals can trigger the interconversion of phenotypes and the plasticity of ILCs, in both mice and humans. Several extrinsic and intrinsic drivers of ILC plasticity have been described. However, the changes in cellular metabolism that underlie ILC plasticity remain largely unexplored. Given that metabolic changes critically affect fate and effector function of several immune cell types, we, here, review recent findings on ILC metabolism and discuss the implications for ILC plasticity.

Candida Infection Associated with Anti-IL-17 Medication: A Systematic Analysis and Review of the Literature.

Anti-interleukin (IL)-17 agents have shown excellent therapeutic efficacy in patients with psoriasis and are expected to be expanded to other chronic inflammatory diseases. However, patients receiving anti-IL-17 agents are at an increased risk of developing Candida infection, with some agents reported to increase the incidence in a dose-dependent manner. Interleukin-17 is secreted by the Th17 subset of CD4+ lymphocytes, CD8+ T cells, and innate cells, including natural killer T cells, lymphoid tissue inducer cells, innate lymphoid cells, and γδ-T cells, and plays an important role in antifungal defense. Genetic defects in the IL-17-signaling pathway in both humans and animal models render susceptibility to candidiasis caused by Candida albicans. The purpose of this narrative review is to evaluate the literature on the role of IL-17 in protection against candidiasis, the prevalence of candidiasis in anti-IL-17 agent use, and to offer clinical recommendations on the diagnosis and management of anti-IL-17 medication-associated candidiasis.

Innate Lymphoid Cells in Autoimmune Diseases.

Innate lymphoid cells (ILC) are a heterogeneous group of immune cells characterized by lymphoid morphology and cytokine profile similar to T cells but which do not express clonally distributed diverse antigen receptors. These particular cells express transcription factors and cytokines reflecting their similarities to T helper (Th)1, Th2, and Th17 cells and are therefore referred to as ILC1, ILC2, and ILC3. Other members of the ILC subsets include lymphoid tissue inducer (LTi) and regulatory ILC (ILCreg). Natural killer (NK) cells share a common progenitor with ILC and also exhibit a lymphoid phenotype without antigen specificity. ILC are found in low numbers in peripheral blood but are much more abundant at barrier sites such as the skin, liver, airways, lymph nodes, and the gastrointestinal tract. They play an important role in innate immunity due to their capacity to respond rapidly to pathogens through the production of cytokines. Recent evidence has shown that ILC also play a key role in autoimmunity, as alterations in their number or function have been identified in systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Here, we review recent advances in the understanding of the role of ILC in the pathogenesis of autoimmune diseases, with particular emphasis on their role as a potential diagnostic biomarker and as therapeutic targets.

Single-cell analyses reveal key immune cell subsets associated with response to PD-L1 blockade in triple-negative breast cancer

In triple-negative breast cancer (TNBC), the benefit of combining chemotherapy with checkpoint inhibitors is still not very clear. We utilize single-cell RNA- and ATAC-sequencing to examine the immune cell dynamics in 22 patients with advanced TNBC treated with paclitaxel or its combination with the anti-PD-L1 atezolizumab. We demonstrate that high levels of baseline CXCL13+ Tcells are linked to the proinflammatory features of macrophages and can predict effective responses to the combination therapy. In responsive patients, lymphoid tissue inducer (LTi) cells, follicular B (Bfoc) cells, CXCL13+ Tcells, and conventional type 1 dendritic cells (cDC1) concertedly increase following the combination therapy, but instead decrease after paclitaxel monotherapy. Our data highlight the importance of CXCL13+ Tcells in effective responses to anti-PD-L1 therapies and suggest that their reduction by paclitaxel regimen may compromise the clinical outcomes of accompanying atezolizumab for TNBC treatment.

ILC3s control airway inflammation by limiting T cell responses to allergens and microbes.

SUMMARYGroup 3 innate lymphoid cells (ILC3s) critically regulate host-microbe interactions in the gastrointestinal tract, but their role in the airway remains poorly understood. Here, we demonstrate that lymphoid-tissue-inducer (LTi)-like ILC3s are enriched in the lung-draining lymph nodes of healthy mice and humans. These ILC3s abundantly express major histocompatibility complex class II (MHC class II) and functionally restrict the expansion of allergen-specific CD4+ T cells upon experimental airway challenge. In a mouse model of house-dust-mite-induced allergic airway inflammation, MHC class II+ ILC3s limit T helper type 2 (Th2) cell responses, eosinophilia, and airway hyperresponsiveness. Furthermore, MHC class II+ ILC3s limit a concomitant Th17 cell response and airway neutrophilia. This exacerbated Th17 cell response requires exposure of the lung to microbial stimuli, which can be found associated with house dust mites. These findings demonstrate a critical role for antigen-presenting ILC3s in orchestrating immune tolerance in the airway by restricting pro-inflammatory T cell responses to both allergens and microbes.

Therapeutic Potential of Innate Lymphoid Cells for Multiple Myeloma Therapy.

Simple SummaryMultiple myeloma (MM) is the second most common haematological malignancy. Despite huge progress associated with the introduction of new antimyeloma drugs, MM remains an incurable disease. In this review, we discuss the role of the innate lymphoid system, its role in the pathogenesis of the disease, and the mechanisms by which innate lymphoid cells (ILC) can theoretically achieve therapeutic benefit in MM treatment.Innate lymphoid cells (ILCs) are a recently identified family of lymphocyte-like cells lacking a specific antigen receptor. They are part of the innate immune system. They play a key role in tissue homeostasis and also control inflammatory and neoplastic processes. In response to environmental stimuli, ILCs change their phenotype and functions, and influence the activity of other cells in the microenvironment. ILC dysfunction can lead to a wide variety of diseases, including cancer. ILC can be divided into three subgroups: ILC Group 1, comprising NK cells and ILC1; Group 2, including ILC2 alone; and Group 3, containing Lymphoid Tissue inducers (LTi) and ILC3 cells. While Group 1 ILCs mainly exert antitumour activity, Group 2 and Group 3 ILCs are protumorigenic in nature. A growing body of preclinical and clinical data support the role of ILCs in the pathogenesis of multiple myeloma (MM). Therefore, targeting ILCs may be of clinical benefit. In this manuscript, we review the available data on the role of ILCs in MM immunology and therapy.

T-bet and RORα control lymph node formation by regulating embryonic innate lymphoid cell differentiation.

The generation of lymphoid tissues during embryogenesis relies on group 3 innate lymphoid cells (ILC3) displaying lymphoid tissue inducer (LTi) activity and expressing the master transcription factor RORγt. Accordingly, RORγt-deficient mice lack ILC3 and lymphoid structures, including lymph nodes (LN). Whereas T-bet affects differentiation and functions of ILC3 postnatally, the role of T-bet in regulating fetal ILC3 and LN formation remains completely unknown. Using multiple mouse models and single-cell analyses of fetal ILCs and ILC progenitors (ILCP), here we identify a key role for T-bet during embryogenesis and show that its deficiency rescues LN formation in RORγt-deficient mice. Mechanistically, T-bet deletion skews the differentiation fate of fetal ILCs and promotes the accumulation of PLZFhi ILCP expressing central LTi molecules in a RORα-dependent fashion. Our data unveil an unexpected role for T-bet and RORα during embryonic ILC function and highlight that RORγt is crucial in counteracting the suppressive effects of T-bet.

The Role of Innate Lymphoid Cells in Chronic Respiratory Diseases.

The lung is a vital mucosal organ that is constantly exposed to the external environment, and as such, its defenses are continuously under threat. The pulmonary immune system has evolved to sense and respond to these danger signals while remaining silent to innocuous aeroantigens. The origin of the defense system is the respiratory epithelium, which responds rapidly to insults by the production of an array of mediators that initiate protection by directly killing microbes, activating tissue-resident immune cells and recruiting leukocytes from the blood. At the steady-state, the lung comprises a large collection of leukocytes, amongst which are specialized cells of lymphoid origin known as innate lymphoid cells (ILCs). ILCs are divided into three major helper-like subsets, ILC1, ILC2 and ILC3, which are considered the innate counterparts of type 1, 2 and 17 T helper cells, respectively, in addition to natural killer cells and lymphoid tissue inducer cells. Although ILCs represent a small fraction of the pulmonary immune system, they play an important role in early responses to pathogens and facilitate the acquisition of adaptive immunity. However, it is now also emerging that these cells are active participants in the development of chronic lung diseases. In this mini-review, we provide an update on our current understanding of the role of ILCs and their regulation in the lung. We summarise how these cells and their mediators initiate, sustain and potentially control pulmonary inflammation, and their contribution to the respiratory diseases chronic obstructive pulmonary disease (COPD) and asthma.

Single-cell transcriptomic landscape reveals tumor specific innate lymphoid cells associated with colorectal cancer progression

SummaryInnate lymphoid cells (ILCs) are tissue-resident lymphocytes differing from conventional T lymphocytes in having no antigen-specific receptors. ILCs include natural killer (NK) cells, helper-like ILC1s, ILC2s, and ILC3s, and lymphoid tissue-inducer (LTi) cells. Tumor ILCs are frequently found in various cancers, but their roles in cancer immunity and immunotherapy remain largely unclear. We report here the single-cell characterization of blood and gut helper-like ILC subsets in healthy conditions and in colorectal cancer (CRC). The healthy gut contains ILC1s, ILC3s, and ILC3/NKs, but no ILC2s. Additional tumor-specific ILC1-like and ILC2 subsets were identified in CRC patients. Signaling lymphocytic activation molecule family member 1 (SLAMF1) was found to be selectively expressed on tumor-specific ILCs, and higher levels of SLAMF1+ ILCs were observed in the blood of CRC patients. The SLAMF1-high group of CRC patients had a significantly higher survival rate than the SLAMF1-low group, suggesting that SLAMF1 is an anti-tumor biomarker in CRC.

Alternative pathways for the development of lymphoid structures in humans

Lymphoid tissue inducer (LTi) cells are critical for inducing the differentiation of most secondary lymphoid organs (SLOs) in mice. In humans, JAK3 and γc deficiencies result in severe combined immunodeficiency (SCIDs) characterized by an absence of T cells, natural killer cells, innate lymphoid cells (ILCs), and presumably LTi cells. Some of these patients have undergone allogeneic stem cell transplantation (HSCT) in the absence of myeloablation, which leads to donor T cell engraftment, while other leukocyte subsets are of host origin. By using MRI to look for SLOs in nine of these patients 16 to 44 y after HSCT, we discovered that SLOs were exclusively found in the three areas of the abdomen that drain the intestinal tract. A postmortem examination of a child with γc-SCID who had died 3.5 mo after HSCT showed corticomedullary differentiation in the thymus, T cell zones in the spleen, and the appendix, but in neither lymph nodes nor Peyer patches. Tertiary lymphoid organs were observed in the lung. No RAR-related orphan receptor-positive LTi cells could be detected in the existing lymphoid structures. These results suggest that while LTi cells are required for the genesis of most SLOs in humans, SLO in the appendix and in gut-draining areas, as well as tertiary lymphoid organs, can be generated likely by LTi cell-independent mechanisms.

Innate lymphoid cells and cancer: Role in tumor progression and inhibition.

Innate lymphoid cells (ILCs), a critical component of the immune system, have recently been nominated as emerging players associated with tumor progression and inhibition. ILCs are classified into five groups: natural killer (NK) cells, ILC1s, ILC2s, ILC3s, and lymphoid tissue inducer (LTis) cells. NK cells and ILC1s are mainly involved in antitumor activities due to their cytotoxic and cytokine production capabilities, respectively. The current understanding of the heterogeneous behavior of ILC2s and ILC3s in tumors is limited and incomplete. Mostly, their dual roles are modulated by their resident tissues, released cytokines, cancer types, and plasticity. Based on overlap RORγt and cytokine expression, the LTi cells were previously considered part of the ILC3s ontogeny, which are essential for the formation of the secondary lymphoid organs during embryogenesis. Indeed, these facts highlight the urgency in understanding the respective mechanisms that shape the phenotypes and responses of ILCs, either on the repressive or proliferative side in the tumor microenvironment (TME). This review aims to provide an updated view of ILCs biology with respect to tumorigenesis, including a description of ILC plasticity, their interaction with other immune cells and communication with components of the TME. Taken together, targeting ILCs for cancer immunotherapy could be a promising approach against tumors that needs to be further study.

B cell residency but not T cell–independent IgA switching in the gut requires innate lymphoid cells

Immunoglobulin A (IgA)-producing plasma cells derived from conventional B cells in the gut play an important role in maintaining the homeostasis of gut flora. Both T cell-dependent and T cell-independent IgA class switching occurs in the lymphoid structures in the gut, whose formation depends on lymphoid tissue inducers (LTis), a subset of innate lymphoid cells (ILCs). However, our knowledge on the functions of non-LTi helper-like ILCs, the innate counter parts of CD4 T helper cells, in promoting IgA production is still limited. By cell adoptive transfer and utilizing a unique mouse strain, we demonstrated that the generation of IgA-producing plasma cells from B cells in the gut occurred efficiently in the absence of both T cells and helper-like ILCs and without engaging TGF-β signaling. Nevertheless, B cell recruitment and/or retention in the gut required functional NKp46-CCR6+ LTis. Therefore, while CCR6+ LTis contribute to the accumulation of B cells in the gut through inducing lymphoid structure formation, helper-like ILCs are not essential for the T cell-independent generation of IgA-producing plasma cells.

Spatial distribution of LTi-like cells in intestinal mucosa regulates type 3 innate immunity

Lymphoid tissue inducer (LTi)-like cells are tissue resident innate lymphocytes that rapidly secrete cytokines that promote gut epithelial integrity and protect against extracellular bacterial infections.Here, we report that the retention of LTi-like cells in conventional solitary intestinal lymphoid tissue (SILT) is essential for controlling LTi-like cell function and is maintained by expression of the chemokine receptor CXCR5. Deletion of Cxcr5 functionally unleashed LTi-like cells in a cell intrinsic manner, leading to uncontrolled IL-17 and IL-22 production. The elevated production of IL-22 in Cxcr5-deficient mice improved gut barrier integrity and protected mice during infection with the opportunistic pathogen Clostridium difficile Interestingly, Cxcr5-/- mice developed LTi-like cell aggregates that were displaced from their typical niche at the intestinal crypt, and LTi-like cell hyperresponsiveness was associated with the local formation of this unconventional SILT. Thus, LTi-like cell positioning within mucosa controls their activity via niche-specific signals that temper cytokine production during homeostasis.

GATA2 participates in the recanalization of lymphatic vessels after surgical lymph node extirpation.

Lymphatic recanalization failure after lymphadenectomy constitutes a major risk of lymphedema in cancer surgery. It has been reported that GATA2, a zinc finger transcription factor, is expressed in lymphatic endothelial cells and is involved in the development of fetal lymphatic vessels. GATA3, another member of the GATA family of transcription factors, is required for the differentiation of lymphoid tissue inducer (LTi) cells and is essential for lymph node formation. However, how GATA2 and GATA3 function in recanalization after the surgical extirpation of lymphatic vessels has not been elucidated. Employing a new model of lymphatic recanalization, we examined the lymphatic reconnection process in Gata2 heterozygous deficient (Gata2+/- ) and Gata3 heterozygous deficient (Gata3+/- ) mice. We found that lymphatic recanalization was significantly impaired in Gata2+/- mice, while Gata3+/- mice rarely showed such abnormalities. Notably, the perturbed lymphatic recanalization in the Gata2+/- mice was partially restored by crossing with the Gata3+/- mice. Our results demonstrate for the first time that GATA2 participates in the regeneration of damaged lymphatic vessels and the unexpected suppressive activity of GATA3 against lymphatic recanalization processes.

Dietary Derived Micronutrients Modulate Immune Responses Through Innate Lymphoid Cells.

Innate lymphoid cells (ILCs) are a group of innate immune cells that possess overlapping features with T cells, although they lack antigen-specific receptors. ILCs consist of five subsets-ILC1, ILC2, ILC3, lymphoid tissue inducer (LTi-like) cells, and natural killer (NK) cells. They have significant functions in mediating various immune responses, protecting mucosal barrier integrity and maintaining tissue homeostasis in the lung, skin, intestines, and liver. ILCs react immediately to signals from internal and external sources. Emerging evidence has revealed that dietary micronutrients, such as various vitamins and minerals can significantly modulate immune responses through ILCs and subsequently affect human health. It has been demonstrated that micronutrients control the development and proliferation of different types of ILCs. They are also potent immunoregulators in several autoimmune diseases and play vital roles in resolving local inflammation. Here, we summarize the interplay between several essential micronutrients and ILCs to maintain epithelial barrier functions in various mucosal tissues and discuss their limitations and potentials for promoting human health.

025 ALA-PDT inhibits skin squamous cell carcinoma (cSCC) via regulating formation of tertiary lymphoid structures

Topical ALA-mediated PDT, ALA-PDT, is a novel therapeutic modality widely used to treat actinic keratosis, Bowen’s Disease, superficial skin SCC, and other cancerous and precancerous skin diseases. Several studies have proved that ALA-PDT can inhibit SCC growth. Subsequent research suggested that ALA-PDT not only directly induced tumor cells apoptosis, but also improve tumor microenvironment through regulation of immune cells. However, the anti-tumor immune function of ALA-PDT is still need to be elucidated. Here, we found that tertiary lymphoid structures (TLSs), which are ectopic lymphoid organs that develop in non-lymphoid tissues at sites of chronic inflammation including tumors, play a pivotal role in anti-tumor immune function of ALA-PDT. We analyzed 77 samples of cSCC patient in our hospital. TLS was observed in 79% of the patient samples, and the density of TLS is negatively correlation with the Brodes classification of cSCC. Intriguingly, immunohistochemistry showed that ALA-PDT could promote the formation of TLS in vivo. We also found that promotion effect of ALA-PDT on TLS is mediated by M1 macrophage, which function as lymphoid tissue inducer cells in TLS formation and recruited by ALA-PDT. Further investigation substantiated that PDT-secreted exosomes were involved in M1 macrophage polarization. Our study elucidated a mechanism that ALA-PDT influence M1 macrophage polarization via PDT-secreted exosomes, which could facilitate the formation of TLS. Thus, our research may contribute to in-depth molecular understanding of the ALA-PDT on anti-tumor immune function.

A wave of bipotent T/ILC-restricted progenitors shapes the embryonic thymus microenvironment in a time-dependent manner

AbstractDuring embryonic development, multiple waves of hematopoietic progenitors with distinct lineage potential are differentially regulated in time and space. Two different waves of thymic progenitors colonize the fetal thymus where they contribute to thymic organogenesis and homeostasis. The origin, the lineage differentiation potential of the first wave, and their relative contribution in shaping the thymus architecture, remained, however, unclear. Here, we show that the first wave of thymic progenitors comprises a unique population of bipotent T and innatel lymphoid cells (T/ILC), generating a lymphoid tissue inducer cells (LTi's), in addition to invariant Vγ5+ T cells. Transcriptional analysis revealed that innate lymphoid gene signatures and, more precisely, the LTi-associated transcripts were expressed in the first, but not in the second, wave of thymic progenitors. Depletion of early thymic progenitors in a temporally controlled manner showed that the progeny of the first wave is indispensable for the differentiation of autoimmune regulator–expressing medullary thymic epithelial cells (mTECs). We further show that these progenitors are of strict hematopoietic stem cell origin, despite the overlap between lymphopoiesis initiation and the transient expression of lymphoid-associated transcripts in yolk sac (YS) erythromyeloid-restricted precursors. Our work highlights the relevance of the developmental timing on the emergence of different lymphoid subsets, required for the establishment of a functionally diverse immune system.

ILC3-derived acetylcholine promotes protease-driven allergic lung pathology

ILC3-derived acetylcholine promotes protease-driven allergic lung pathology

Innate Lymphoid Cells in Human Pregnancy.

Innate lymphoid cells (ILCs) are a new set of cells considered to be a part of the innate immune system. ILCs are classified into five subsets (according to their transcription factors and cytokine profile) as natural killer cells (NK cells), group 1 ILCs, group 2 ILCs, group 3 ILCs, and lymphoid tissue inducers (LTi). Functionally, these cells resemble the T helper population but lack the expression of recombinant genes, which is essential for the formation of T cell receptors. In this work, the authors address the distinction between peripheral and decidual NK cells, highlighting their diversity in ILC biology and its relevance to human pregnancy. ILCs are effector cells that are important in promoting immunity, inflammation, and tissue repair. Recent studies have directed their attention to ILC actions in pregnancy. Dysregulation or expansion of pro-inflammatory ILC populations as well as abnormal tolerogenic responses may directly interfere with pregnancy, ultimately resulting in pregnancy loss or adverse outcomes. In this review, we characterize these cells, considering recent findings and addressing knowledge gaps in perinatal medicine in the context of ILC biology. Moreover, we discuss the relevance of these cells not only to the process of immune tolerance, but also in disease.