The ERM Protein Moesin Regulates CD8+ Regulatory T Cell Homeostasis and Self-Tolerance

Novel Mutation in the Moesin (MSN) Gene Leads to Immunodeficiency with Epstein-Barr Virus (EBV) Infection and Dermatomyositis-Like Symptoms

PURPOSE

Moesin (MSN) deficiency is a recently reported combined immunodeficiency, and few cases have been reported to date. We describe a Chinese patient with a novel mutation causing MSN deficiency and a novel phenotype.

METHODS

Clinical and immunological data were collected. Whole-exome sequencing was performed to identify gene mutations. MSN protein expression and T cell proliferation and activation were determined by flow cytometry. Cell migration was confirmed with a Transwell assay. Autoantibody levels were analyzed using antigen microarrays.

RESULTS

The patient was a 10-year-old boy who presented with recurrent fever, oral ulcers and dermatomyositis-like symptoms, such as periorbital edema, facial swelling, elevated creatine kinase levels, and abnormal electromyography and muscle biopsy results. Epstein-Barr virus (EBV) DNA was detected in the serum, cells and tissues of this patient. He further developed nasal-type NK/T-cell lymphoma. A novel hemizygous mutation (c.68 A > G, p.N23S) in the MSN gene was found. The immunological phenotype of this patient included persistent decreases in T and B lymphocyte counts but normal immunoglobulin IgG levels. The patient had attenuated MSN protein expression and impaired T-cell proliferation and migration. The proportions of Tfh cells and CD21low B cells in the patient were higher than those in the controls. Moreover, 82 IgG and 102 IgM autoantibodies were more abundant in the patient than in the healthy controls.

CONCLUSIONS

The novel mutation N23S is pathogenic and leads to a severe clinical phenotype. EBV infection, tumor, and dermatomyositis-like autoimmune symptoms may be associated with MSN deficiency, further expanding the understanding of the disease.

Moesin deficiency leads to lupus-like nephritis with accumulation of CXCL13-producing patrolling monocytes

Moesin is a member of the ezrin-radixin-moesin (ERM) family of proteins that link plasma membrane proteins to the cortical cytoskeleton and thus regulate diverse cellular processes. Mutations in the human moesin gene cause a primary immunodeficiency called X-linked moesin-associated immunodeficiency (X-MAID), which may be complicated by an autoimmune phenotype with kidney involvement. We previously reported that moesin-deficient mice exhibit lymphopenia similar to that of X-MAID and develop a lupus-like autoimmune phenotype with age. However, the mechanism through which moesin defects cause kidney pathology remains obscure. Here, we characterized immune cell infiltration and chemokine expression in the kidney of moesin-deficient mice. We found accumulation of CD4+ T and CD11b+ myeloid cells and high expression of CXCL13, whose upregulation was detected before the onset of overt nephritis. CD4+ T cell population contained IFN-γ-producing effectors and expressed the CXCL13 receptor CXCR5. Among myeloid cells, Ly6Clo patrolling monocytes and MHCIIlo macrophages markedly accumulated in moesin-deficient kidneys and expressed high CXCL13 levels, implicating the CXCL13-CXCR5 axis in nephritis development. Functionally, Ly6Clo monocytes from moesin-deficient mice showed reduced migration toward sphingosine 1-phosphate. These findings suggest that moesin plays a role in regulating patrolling monocyte homeostasis, and that its defects lead to nephritis associated with accumulation of CXCL13-producing monocytes and macrophages.

Moesin activation controls bone resorption and tunneling nanotube-dependent osteoclast fusion

Osteoclasts are multinucleated cells unique in their ability to resorb bone. Osteoclastogenesis involves several steps of actin-driven rearrangements that participate not only in the cell-cell fusion process, but also in the formation of the sealing zone, the adhesive structure determining the resorption area. Despite the importance of these actin cytoskeleton-based processes, their precise mechanisms of regulation are still poorly characterized. Here, we found that moesin, a member of the Ezrin/Radixin/Moesin (ERM) protein family, is activated during osteoclast maturation and plays an instrumental role for both osteoclast fusion and function. In mouse and human osteoclast precursors, moesin is negatively regulated to potentiate their ability to fuse and degrade bone. Accordingly, we demonstrated that moesin depletion decreases membrane-to-cortex attachment and enhances formation of tunneling nanotubes (TNTs), F-actin-containing intercellular bridges that we revealed to trigger osteoclast fusion. In addition, via a β3-integrin/RhoA/SLK pathway and independently of its role in fusion, moesin regulates the number and organization of sealing zones in mature osteoclast, and thus participates in the control of bone resorption. Supporting these findings, we found that moesin-deficient mice are osteopenic with a reduced density of trabecular bones and increased osteoclast abundance and activity. These findings provide a better understanding of the regulation of osteoclast biology, and open new opportunities to specifically target osteoclast activity in bone disease therapy.

Helios as a Potential Biomarker in Systemic Lupus Erythematosus and New Therapies Based on Immunosuppressive Cells

The Helios protein (encoded by the IKZF2 gene) is a member of the Ikaros transcription family and it has recently been proposed as a promising biomarker for systemic lupus erythematosus (SLE) disease progression in both mouse models and patients. Helios is beginning to be studied extensively for its influence on the T regulatory (Treg) compartment, both CD4+ Tregs and KIR+/Ly49+ CD8+ Tregs, with alterations to the number and function of these cells correlated to the autoimmune phenomenon. This review analyzes the most recent research on Helios expression in relation to the main immune cell populations and its role in SLE immune homeostasis, specifically focusing on the interaction between T cells and tolerogenic dendritic cells (tolDCs). This information could be potentially useful in the design of new therapies, with a particular focus on transfer therapies using immunosuppressive cells. Finally, we will discuss the possibility of using nanotechnology for magnetic targeting to overcome some of the obstacles related to these therapeutic approaches.

Inherited human ezrin deficiency impairs adaptive immunity

BACKGROUND

Inborn errors of immunity (IEI) are a group of monogenic diseases that confer susceptibility to infection, autoimmunity, and cancer. Despite the life-threatening consequences of some IEI, their genetic cause remains unknown in many patients.

OBJECTIVE

We investigated a patient with an IEI of unknown genetic etiology.

METHODS

Whole-exome sequencing identified a homozygous missense mutation of the gene encoding ezrin (EZR), substituting a threonine for an alanine at position 129.

RESULTS

Ezrin is one of the subunits of the ezrin, radixin, and moesin (ERM) complex. The ERM complex links the plasma membrane to the cytoskeleton and is crucial for the assembly of an efficient immune response. The A129T mutation abolishes basal phosphorylation and decreases calcium signaling, leading to complete loss of function. Consistent with the pleiotropic function of ezrin in myriad immune cells, multidimensional immunophenotyping by mass and flow cytometry revealed that in addition to hypogammaglobulinemia, the patient had low frequencies of switched memory B cells, CD4+ and CD8+ T cells, MAIT, γδ T cells, and centralnaive CD4+ cells.

CONCLUSIONS

Autosomal-recessive human ezrin deficiency is a newly recognized genetic cause of B-cell deficiency affecting cellular and humoral immunity.

A Novel Variant of X-Linked Moesin Gene in a Boy With Inflammatory Bowel Disease Like Disease-A Case Report

Variants in the MSN gene were recently reported as the cause of a primary immunodeficiency disease called X-linked moesin-associated immunodeficiency (X-MAID). Hitherto, only 10 patients were reported worldwide. Here, we report a boy who presented with recurrent high fever, oral ulcers, abdominal pain, and hematochezia for over 2 weeks. His serum inflammatory markers were elevated, and colonoscopy showed multiple colon ulcers and terminal ileum ulcers which resemble colitis caused by inflammatory bowel disease. A novel heterozygous variant c.934G>T(p.Glu312Ter) in the MSN gene was identified using whole exome sequencing (WES) and trio analysis. Intestinal ulcers were almost healed after inducing therapy with steroids and maintenance treatment of anti-TNFα therapy. We summarized the genotype and phenotype of reported X-MAID patients and presented the patient’s unique phenotype in this study. This study also expanded the spectrum of MSN mutation-caused immunodeficiency.

Helios Expression Is Downregulated on CD8+ Treg in Two Mouse Models of Lupus During Disease Progression

T-cell–mediated autoimmunity reflects an imbalance in this compartment that is not restored by tolerogenic immune cells, e.g., regulatory T cells or tolerogenic dendritic cells (tolDCs). Although studies into T-cell equilibrium have mainly focused on regulatory CD4⁺FoxP3⁺ T cells (CD4⁺ Tregs), recent findings on the lesser known CD8⁺ Tregs (CD44⁺CD122⁺Ly49⁺) have highlighted their non-redundant role in regulating lupus-like disease and their regulatory phenotype facilitated by the transcription factor Helios in mice and humans. However, there are still remaining questions about Helios regulation and dynamics in different autoimmune contexts. Here, we show the absence of CD8⁺ Tregs in two lupus-prone murine models: MRL/MPJ and MRL/lpr, in comparison with a non-prone mouse strain like C57BL/6. We observed that all MRL animals showed a dramatically reduced population of CD8⁺ Tregs and a greater Helios downregulation on diseased mice. Helios induction was detected preferentially on CD8⁺ T cells from OT-I mice co-cultured with tolDCs from C57BL/6 but not in MRL animals. Furthermore, the Helios profile was also altered in other relevant T-cell populations implicated in lupus, such as CD4⁺ Tregs, conventional CD4⁺, and double-negative T cells. Together, these findings could make Helios a versatile maker across the T-cell repertoire that is capable of differentiating lupus disease states.

Plasma Exosomal Proteomic Pattern of Epstein-Barr Virus-Associated Hemophagocytic Lymphohistiocytosis

Epstein-Barr virus (EBV)-associated hemophagocytic lymphohistiocytosis (EBV-HLH) is a life-threatening syndrome, which is caused by EBV infection that is usually refractory to treatment and shows relapse. The development of new biomarkers for the early diagnosis and clinical treatment of EBV-HLH is urgently needed. Exosomes have been shown to mediate various biological processes and are ideal non-invasive biomarkers. Here, we present the differential plasma exosomal proteome of a patient with EBV-HLH before vs. during treatment and with that of his healthy twin brother. A tandem mass tag-labeled LC-MS technique was employed for proteomic detection. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses indicated that differential proteomic profiles were related to virus infection, coagulopathy, nervous system dysfunction, imbalance of immune response, and abnormal liver function. The candidate biomarkers were first identified in the patient’s plasma exosomes at different treatment and follow-up time points. Then, 14 additional EBV-HLH exosome samples were used to verify six differentially expressed proteins. The upregulation of C-reactive protein, moesin, galectin three-binding protein, and heat shock cognate 71 kDa protein and the downregulation of plasminogen and fibronectin 1 could serve as potential biomarkers of EBV-HLH. This plasma exosomal proteomic analysis provides new insights into the diagnostic and therapeutic biomarkers of EBV-HLH.

Thrombospondin-1, Platelet Factor 4, and Galectin-1 are Associated with Engraftment in Patients with Sickle Cell Disease Who Underwent Haploidentical HSCT

Sickle cell disease (SCD) is an inherited red blood cell disorder that leads to significant morbidity and early mortality. The most widely available curative approach remains allogeneic hematopoietic stem cell transplantation (HSCT). HLA-haploidentical (haplo) HSCT expands the donor pool considerably and is a practical alternative for these patients, but traditionally with an increased risk of allograft rejection. Biomarkers in patient plasma could potentially help predict HSCT outcome and allow treatment at an early stage to reverse or prevent graft rejection. Reliable, noninvasive methods to predict engraftment or rejection early after HSCT are needed. We sought to detect variations in the plasma proteomes of patients who engrafted compared with those who rejected their grafts. We used a mass spectrometry-based proteomics approach to identify candidate biomarkers associated with engraftment and rejection by comparing plasma samples obtained from 9 engrafted patients and 10 patients who experienced graft rejection. A total of 1378 proteins were identified, 45 of which were differentially expressed in the engrafted group compared with the rejected group. Based on bioinformatics analysis results, information from the literature, and immunoassay availability, 7 proteins-thrombospondin-1 (Tsp-1), platelet factor 4 (Pf-4), talin-1, moesin, cell division control protein 42 homolog (CDC42), galectin-1 (Gal-1), and CD9-were selected for further analysis. We compared these protein concentrations among 35 plasma samples (engrafted, n = 9; rejected, n = 10; healthy volunteers, n = 8; nontransplanted SCD, n = 8). ELISA analysis confirmed the significant up-regulation of Tsp-1, Pf-4, and Gal-1 in plasma samples from engrafted patients compared with rejected patients, healthy African American volunteers, and the nontransplanted SCD group (P < .01). By receiver operating characteristic analysis, these 3 proteins distinguished engrafted patients from the other groups (area under the curve, >0.8; P < .05). We then evaluated the concentration of these 3 proteins in samples collected pre-HSCT and at days +30, +60, +100, and +180 post-HSCT. The results demonstrate that Tsp-1 and Pf-4 stratified engrafted patients as early as day 60 post-HSCT (P < .01), and that Gal-1 was significantly higher in engrafted patients as early as day 30 post-HSCT (P < .01). We also divided the rejected group into those who experienced primary (n = 5) and secondary graft rejection (n = 5) and found that engrafted patients had significantly higher Tsp-1 levels compared with patients who developed primary graft rejection at days +60 and +100 (P < .05), as well as higher Pf-4 levels compared with patients who developed primary graft rejection at post-transplantation (PT) day 100. Furthermore, Tsp-1 levels were significantly higher at PT days 60 and 100 and Pf-4 levels were higher at PT day 100 in engrafted patients compared with those who experienced secondary graft rejection. Increased concentrations of plasma Gal-1, Tsp-1, and Pf-4 could reflect increased T regulatory cells, IL-10, and TGF-β, which are essential players in the initiation of immunologic tolerance. These biomarkers may provide opportunities for preemptive intervention to minimize the incidence of graft rejection.

Expression Dynamics of the O-Glycosylated Proteins Recognized by Amaranthus leucocarpus Lectin in T Lymphocytes and Its Relationship With Moesin as an Alternative Mechanism of Cell Activation

T lymphocyte activation begins with antigen/MHC recognition by the TCR/CD3 complex followed by a costimulatory signal provided by CD28. The search for novel costimulatory molecules has been extensive due to their potential use as immunotherapeutic targets. Although some molecules have been identified, they are unable to provide sustainable signaling to allow for proper T cell activation and proliferation. It has been shown that the Amaranthus leucocarpus lectin (ALL) can be used as an in vitro costimulator of CD4+ lymphocytes in the presence of anti-CD3 mAb; this lectin specifically recognizes O-glycans of the Galβ1-3GalNAc-O-Ser/Thr type, including a 70-kDa moesin-like protein that has been suggested as the costimulatory molecule. However, the identity of this molecule has not been confirmed and such costimulation has not been analyzed in CD8+ lymphocytes. We show herein that the expression kinetics of the glycoproteins recognized by ALL (gpALL) is different in CD4+ and CD8+ T cells, unlike moesin expression. Results from IP experiments demonstrate that the previously described 70-kDa moesin-like protein is an O-glycosylated form of moesin (O-moesin) and that in vitro stimulation with anti-CD3 and anti-moesin mAb induces expression of the activation molecules CD69 and CD25, proliferation and IL-2 production as efficiently as cells costimulated with ALL or anti-CD28. Overall, our results demonstrate that O-moesin is expressed in CD4+ and CD8+ T lymphocytes and that moesin provides a new costimulatory activation signal in both T cell subsets.

Crosstalk between basal extracellular matrix adhesion and building of apical architecture during morphogenesis

Tissues build complex structures like lumens and microvilli to carry out their functions. Most of the mechanisms used to build these structures rely on cells remodelling their apical plasma membranes, which ultimately constitute the specialised compartments. In addition to apical remodelling, these shape changes also depend on the proper attachment of the basal plasma membrane to the extracellular matrix (ECM). The ECM provides cues to establish apicobasal polarity, and it also transduces forces that allow apical remodelling. However, physical crosstalk mechanisms between basal ECM attachment and the apical plasma membrane remain understudied, and the ones described so far are very diverse, which highlights the importance of identifying the general principles. Here, we review apicobasal crosstalk of two well-established models of membrane remodelling taking place during Drosophila melanogaster embryogenesis: amnioserosa cell shape oscillations during dorsal closure and subcellular tube formation in tracheal cells. We discuss how anchoring to the basal ECM affects apical architecture and the mechanisms that mediate these interactions. We analyse this knowledge under the scope of other morphogenetic processes and discuss what aspects of apicobasal crosstalk may represent widespread phenomena and which ones are used to build subsets of specialised compartments.

The ERM protein moesin regulates natural killer cell homeostasis in vivo

Moesin is a member of the ezrin-radixin-moesin (ERM) family of proteins that link plasma membrane proteins with actin filaments in the cell cortex. Hemizygous mutations in the X-linked moesin gene are associated with primary immunodeficiency with T and B cell lymphopenia, which also affects natural killer (NK) cells in most cases. We previously showed that moesin deficiency in mice substantially affects lymphocyte homeostasis, but its impact on NK cells remains unexplored. Here, we found that in moesin-deficient mice, NK cells were decreased in the peripheral blood and bone marrow but increased in the spleen. Analysis of female heterozygous mice showed a selective advantage for moesin-expressing NK cells in the blood. Moesin-deficient NK cells exhibited increased cell death and impaired signaling in response to IL-15, suggesting that moesin regulates NK cell survival through IL-15-mediated signaling. Our findings thus identify moesin as an NK cell homeostasis regulator in vivo.

Citrullinated fibrinogen is a target of auto-antibodies in interstitial lung disease in mice with collagen-induced arthritis

Interstitial lung disease (ILD) is a very common and lethal complication of rheumatoid arthritis (RA), yet its pathogenesis is not well understood, in part due to the lack of adequate animal models. Although collagen-induced arthritis (CIA) is the most widely used animal model for RA, the lung involvement occurring in this model has scarcely been studied. To evaluate the suitability of CIA as a model for RA-associated ILD (RA-ILD), we immunized DBA/1 mice with bovine type II collagen and characterized lung disease in this model. Histologic analyses revealed patchy interstitial infiltration of inflammatory cells in the peripheral regions of the lung, notably in the subpleural region, in mice with CIA. This pattern resembled usual interstitial pneumonia in humans, which is the most prevalent pattern in RA-ILD. Among infiltrates in the lung, CD11bhi macrophages of the M2 phenotype were most prominently increased. IgG and C3 were deposited in the subpleural region where inflammatory cells infiltrated. The sera from CIA mice contained auto-antibodies against citrullinated proteins, which are specific and predictive markers for RA. Protein citrullination was enhanced in the lung of CIA mice compared with naive mice, and citrullinated fibrinogen was primarily targeted by these auto-antibodies. The elevation of auto-antibodies against citrullinated proteins and their deposition in the lung with patchy subpleural preponderance suggest that CIA can serve as a model to study the pathogenesis of RA-ILD.

CD8+ Regulatory T Cell - A Mystery to Be Revealed

Regulatory T cells (Treg) are essential to maintain immune homeostasis and prevent autoimmune disorders. While the function and molecular regulation of Foxp3+CD4+ Tregs are well established, much of CD8+ Treg biology remains to be revealed. Here, we will review the heterogenous subsets of CD8+ T cells have been named "CD8+ Treg" and mainly focus on CD122hiLy49+CD8+ Tregs present in naïve mice. CD122hiLy49+CD8+ Tregs, which depends on transcription factor Helios and homeostatic cytokine IL-15, have been established as a non-redundant regulator of germinal center (GC) reaction. Recently, we have demonstrated that TGF-β (Transforming growth factor-β) and transcription factor Eomes (Eomesodermin) are essential for the function and homeostasis of CD8+ Tregs. In addition, we will discuss several open questions regarding the differentiation, function and true identity of CD8+ Tregs as well as a brief comparison between two regulatory T cell subsets critical to control GC reaction, namely CD4+ TFR (follicular regulatory T cells) and CD8+ Tregs.

Functional Characterization of Ly49+CD8 T-Cells in Both Normal Condition and During Anti-Viral Response

The role of Ly49+CD8 T-cells in the immune system is not clear. Previously, several papers suggested Ly49+CD8 T-cells as immunosuppressors, while multiple studies also suggested their role as potent participants of the immune response. The mechanism of Ly49 expression on CD8 T-cells is also not clear. We investigated phenotype, functions, and regulation of Ly49 expression on murine CD8 T-cells in both normal state and during LCMV infection. CD8 T-cells express different Ly49 receptors compared with NK-cells. In intact mice, Ly49+CD8 T-cells have a phenotype similar to resting central memory CD8 T-cells and do not show impaired proliferation and cytokine production. Conventional CD8 T-cells upregulate Ly49 receptors during TCR-induced stimulation, and IL-2, as well as IL-15, affect it. At the same time, Ly49+CD8 T-cells change the Ly49 expression profile dramatically upon re-stimulation downregulating inhibitory and upregulating activating Ly49 receptors. We observed the expression of Ly49 receptors on the virus-specific CD8 T-cells during LCMV infection, especially marked in the early stages, and participation of Ly49+CD8 T-cells in the anti-viral response. Thus, CD8 T-cells acquire Ly49 receptors during the T-cell activation and show dynamic regulation of Ly49 receptors during stimulation.

ERM Proteins at the Crossroad of Leukocyte Polarization, Migration and Intercellular Adhesion

Ezrin, radixin and moesin proteins (ERMs) are plasma membrane (PM) organizers that link the actin cytoskeleton to the cytoplasmic tail of transmembrane proteins, many of which are adhesion receptors, in order to regulate the formation of F-actin-based structures (e.g., microspikes and microvilli). ERMs also effect transmission of signals from the PM into the cell, an action mainly exerted through the compartmentalized activation of the small Rho GTPases Rho, Rac and Cdc42. Ezrin and moesin are the ERMs more highly expressed in leukocytes, and although they do not always share functions, both are mainly regulated through phosphatidylinositol 4,5-bisphosphate (PIP₂) binding to the N-terminal band 4.1 protein-ERM (FERM) domain and phosphorylation of a conserved Thr in the C-terminal ERM association domain (C-ERMAD), exerting their functions through a wide assortment of mechanisms. In this review we will discuss some of these mechanisms, focusing on how they regulate polarization and migration in leukocytes, and formation of actin-based cellular structures like the phagocytic cup-endosome and the immune synapse in macrophages/neutrophils and lymphocytes, respectively, which represent essential aspects of the effector immune response.

Hematopoietic Stem Cell Transplant for the Treatment of X-MAID

We report outcomes after hematopoietic stem cell transplant for three patients with X-MAID, including 1 patient from the originally described cohort and two brothers with positive TREC newborn screening for SCID who were found to have a T-B-NK+ SCID phenotype attributable to X-linked moesin associated immunodeficiency (X-MAID). A c.511C>T variant in moesin was identified via exome sequencing in the older of these siblings in the setting of low lymphocyte counts and poor proliferative responses consistent with SCID. He received reduced intensity conditioning due to CMV, and was transplanted with a T-depleted haploidentical (maternal) donor. His post-transplant course was complicated by hemolytic anemia, neutropenia, and sepsis. He had poor engraftment, requiring a 2nd transplant. His younger brother presented with the same clinical phenotype and was treated with umbilical cord blood transplant following myeloablative conditioning, has engrafted and is doing well. The third case also presented with severe lymphopenia in infancy, received a matched related bone marrow transplant following myeloablative conditioning, has engrafted and is doing well. These cases represent a novel manifestation of non-radiosensitive X-linked form of T-B-NK+ SCID that is able to be detected by TREC based newborn screening and effectively treated with HCT.

Aberrant T Cell Signaling and Subsets in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic multi-organ debilitating autoimmune disease, which mainly afflicts women in the reproductive years. A complex interaction of genetics, environmental factors and hormones result in the breakdown of immune tolerance to "self" leading to damage and destruction of multiple organs, such as the skin, joints, kidneys, heart and brain. Both innate and adaptive immune systems are critically involved in the misguided immune response against self-antigens. Dendritic cells, neutrophils, and innate lymphoid cells are important in initiating antigen presentation and propagating inflammation at lymphoid and peripheral tissue sites. Autoantibodies produced by B lymphocytes and immune complex deposition in vital organs contribute to tissue damage. T lymphocytes are increasingly being recognized as key contributors to disease pathogenesis. CD4 T follicular helper cells enable autoantibody production, inflammatory Th17 subsets promote inflammation, while defects in regulatory T cells lead to unchecked immune responses. A better understanding of the molecular defects including signaling events and gene regulation underlying the dysfunctional T cells in SLE is necessary to pave the path for better management, therapy, and perhaps prevention of this complex disease. In this review, we focus on the aberrations in T cell signaling in SLE and highlight therapeutic advances in this field.