Humoral Arm Of Innate Immunity Research Articles

Recognition and inhibition of SARS-CoV-2 by humoral innate immunity pattern recognition molecules.

The humoral arm of innate immunity includes diverse molecules with antibody-like functions, some of which serve as disease severity biomarkers in coronavirus disease 2019 (COVID-19). The present study was designed to conduct a systematic investigation of the interaction of human humoral fluid-phase pattern recognition molecules (PRMs) with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Of 12 PRMs tested, the long pentraxin 3 (PTX3) and mannose-binding lectin (MBL) bound the viral nucleocapsid and spike proteins, respectively. MBL bound trimeric spike protein, including that of variants of concern (VoC), in a glycan-dependent manner and inhibited SARS-CoV-2 in three in vitro models. Moreover, after binding to spike protein, MBL activated the lectin pathway of complement activation. Based on retention of glycosylation sites and modeling, MBL was predicted to recognize the Omicron VoC. Genetic polymorphisms at the MBL2 locus were associated with disease severity. These results suggest that selected humoral fluid-phase PRMs can play an important role in resistance to, and pathogenesis of, COVID-19, a finding with translational implications.

Serum amyloid P component is an essential element of resistance against Aspergillus fumigatus

Serum amyloid P component (SAP, also known as Pentraxin 2; APCS gene) is a component of the humoral arm of innate immunity involved in resistance to bacterial infection and regulation of tissue remodeling. Here we investigate the role of SAP in antifungal resistance. Apcs−/− mice show enhanced susceptibility to A. fumigatus infection. Murine and human SAP bound conidia, activate the complement cascade and enhance phagocytosis by neutrophils. Apcs−/− mice are defective in vivo in terms of recruitment of neutrophils and phagocytosis in the lungs. Opsonic activity of SAP is dependent on the classical pathway of complement activation. In immunosuppressed mice, SAP administration protects hosts against A. fumigatus infection and death. In the context of a study of hematopoietic stem-cell transplantation, genetic variation in the human APCS gene is associated with susceptibility to invasive pulmonary aspergillosis. Thus, SAP is a fluid phase pattern recognition molecule essential for resistance against A. fumigatus.

PTX3 Effects on Osteogenic Differentiation in Osteoporosis: An In Vitro Study.

Pentraxin 3 (PTX3) is a glycoprotein belonging to the humoral arm of innate immunity that participates in the body’s defence mechanisms against infectious diseases. It has recently been defined as a multifunctional protein, given its involvement in numerous physiological and pathological processes, as well as in the pathogenesis of age-related diseases such as osteoporosis. Based on this evidence, the aim of our study was to investigate the possible role of PTX3 in both the osteoblastic differentiation and calcification process: to this end, primary osteoblast cultures from control and osteoporotic patients were incubated with human recombinant PTX3 (hrPTX3) for 72 h. Standard osteinduction treatment, consisting of β-glycerophosphate, dexamethasone and ascorbic acid, was used as control. Our results showed that treatment with hrPTX3, as well as with the osteogenic cocktail, induced cell differentiation towards the osteoblastic lineage. We also observed that the treatment not only promoted an increase in cell proliferation, but also the formation of calcification-like structures, especially in primary cultures from osteoporotic patients. In conclusion, the results reported here suggest the involvement of PTX3 in osteogenic differentiation, highlighting its osteoinductive capacity, like the standard osteoinduction treatment. Therefore, this study opens new and exciting perspectives about the possible role of PTX3 as biomarker and therapeutic agent for osteoporosis.

The Role of PTX3 in Mineralization Processes and Aging-Related Bone Diseases

The Long Pentraxin 3 (PTX3) is a multifunctional glycoprotein released by peripheral blood leukocytes and myeloid dendritic cells in response to primary pro-inflammatory stimuli, that acts as a non-redundant component of the humoral arm of innate immunity. In addition to the primary role in the acute inflammatory response, PTX3 seems to be involved in other physiological and pathological processes. Indeed, PTX3 seems to play a pivotal role in the deposition and remodeling of bone matrix during the mineralization process, promoting osteoblasts differentiation and activity. Recently, PTX3 was seen to be involved in the ectopic calcifications’ formation in breast cancer disease. In this regard, it has been observed that breast cancer tumors characterized by high expression of PTX3 and high amount of Breast Osteoblast Like Cells (BOLCs) showed several Hydroxyapatite (HA) microcalcifications, suggesting a likely role for PTX3 in differentiation and osteoblastic activity in both bone and extra-bone sites. Furthermore, given its involvement in bone metabolism, several studies agree with the definition of PTX3 as a molecule significantly involved in the pathogenesis of age-related bone diseases, such as osteoporosis, both in mice and humans. Recent results suggest that genetic and epigenetic mechanisms acting on PTX3 gene are also involved in the progression of these diseases. Based on these evidences, the aim of our systemic review was to offer an overview of the variety of biological processes in which PTX3 is involved, focusing on bone mineralization, both in a physiological and pathological context.

Evolutionary and transcriptional analyses of a pentraxin-like component family involved in the LPS inflammatory response of Ciona robusta

Pentraxins (PTXs) are a superfamily of conserved proteins which are components of the humoral arm of innate immunity. They are considered to be functional ancestors of antibodies and are classified into short and long types. In this study, we show that a pentraxin-like component (Ptx-like) with a C-terminal PTX domain, highly homologous to the short PTX of H. sapiens CRP, and a long N-terminal domain typical of long PTXs, is involved in the inflammatory response of Ciona robusta under LPS exposure in vivo. Analyses of protein domains as well as 3D modelling and phylogenetic tree supported the close relationship of Ptx-like with mammalian CRP, suggesting that C. robusta Ptx-like shares a common ancestor in the chordate lineages. qRT-PCR analysis showed that Ptx-like was transcriptionally upregulated during the inflammatory process induced by LPS inoculation and that it is involved in the initial phase as well as the secondary phase of the inflammatory response in which matrix remodelling and the achievement of homeostasis occur. In situ hybridisation assays revealed that gene transcription was upregulated in the pharynx post-LPS challenge in vivo, and that Ptx-like was expressed by clusters of haemocytes, mainly granulocytes, inside the pharynx vessels. We also found transcript-expressing granulocytes flowing in the musculature and in the lacunae of the circulatory system. These data supported that Ptx-like is a potential molecule of the acute-phase response in C. robusta immune defence systems against bacterial infection.

Pentraxin 3 Plays A Key Role In The Immunomodulation Of Diet Induced-Obesity In Mice

Background and Aims: PTX3, an essential component of the humoral arm of innate immunity, increases during the onset of metabolic disorders. Aim of this project was to clarify whether PTX3 behaves as a bystander or actively participates to obesity-related inflammation.

Role of a fluid-phase PRR in fighting an intracellular pathogen: PTX3 in Shigella infection.

Shigella spp. are pathogenic bacteria that cause bacillary dysentery in humans by invading the colonic and rectal mucosa where they induce dramatic inflammation. Here, we have analyzed the role of the soluble PRR Pentraxin 3 (PTX3), a key component of the humoral arm of innate immunity. Mice that had been intranasally infected with S. flexneri were rescued from death by treatment with recombinant PTX3. In vitro PTX3 exerts the antibacterial activity against Shigella, impairing epithelial cell invasion and contributing to the bactericidal activity of serum.PTX3 is produced upon LPS-TLR4 stimulation in accordance with the lipid A structure of Shigella. In the plasma of infected patients, the level of PTX3 amount only correlates strongly with symptom severity. These results signal PTX3 as a novel player in Shigella pathogenesis and its potential role in fighting shigellosis. Finally, we suggest that the plasma level of PTX3 in shigellosis patients could act as a biomarker for infection severity.

The long pentraxin 3 (PTX3) plays a key role in the immunomodulation of diet induced-obesity in mice

Aim: Chronic low-grade inflammation characterizes metabolic syndrome. Our aim was to study the role of PTX3, an essential component of the humoral arm of innate immunity, during HFD induced-obesity.

Preoperative methylprednisolone increases plasma Pentraxin 3 early after total knee arthroplasty: a randomized, double-blind, placebo-controlled trial.

Preoperative glucocorticoid administration reduces the systemic inflammatory response. Pentraxin 3 (PTX3) is a novel inflammatory marker belonging to the humoral arm of innate immunity exerting a potentially protective host response. This study evaluated PTX3 and other complement marker changes after preoperative methylprednisolone (MP) early after total knee arthroplasty (TKA). Seventy patients were randomized (1:1) to preoperative intravenous (i.v.) MP 125 mg (group MP) or isotonic saline i.v. (group C). The outcomes included change in plasma PTX3, mannose-binding lectin (MBL), ficolins (ficolin-1, -2 and -3), complement components (C4 and C3), terminal complement complex (TCC) and C-reactive protein (CRP) concentrations. Blood samples were analysed at baseline and 2, 6, 24 and 48 h after surgery with complete sampling from 63 patients for analyses. MP resulted in an increase in circulating PTX3 compared to saline from baseline to 24 h postoperatively (P < 0·001), while MP reduced the systemic inflammatory response (CRP) 24 and 48 h postoperatively (P < 0·001). However, the small postoperative changes in MBL, ficolin-1, -2 and -3, C4, C3 and TCC concentrations did not differ between groups (P > 0·05). In conclusion, preoperative MP 125 mg increased circulating PTX3 and reduced the general inflammatory response (CRP) early after TKA, but did not affect other complement markers.

Collectins in urinary tract and kidney diseases.

The innate immune system serves as the frontline defense against invading pathogens and initiates an inflammatory response to microorganisms. Collectins are C-type lectins that are structurally characterized by a collagen-like sequence and a carbohydrate recognition domain. Moreover, they are widely expressed throughout the body and are involved in the innate immunity against a variety of pathogens, regulating inflammation, and protecting the lungs from pathogens. Recently, two classical collectins, surfactant protein A (SP-A) and surfactant protein D (SP-D), as well as novel collectin 11, were found present in urinary tract tissues. They are increasingly recognized as key players in activating the humoral arm of innate immunity and host defense in urinary tract and kidney diseases, although their biological features, functions, and mechanisms in this regard remain largely unclear. In this review, we aim to integrate results reported by ourselves and others to summarize and gain a better understanding of the functions of collectins (SP-A, SP-D, and collectin 11) in urinary tract and kidney diseases.

Abstract SY06-01: Tumor-associated myelomonocytic cells as therapeutic targets

Abstract SY06-01: Tumor-associated myelomonocytic cells as therapeutic targets

Epigenetic regulation of the extrinsic oncosuppressor PTX3 gene in inflammation and cancer

ABSTRACTPTX3 is a component of the humoral arm of innate immunity and an extrinsic oncosuppressor gene taming tumor-promoting inflammation. Here, we show that two enhancers differently regulate PTX3 expression: enhancer 1, located 230 kb upstream of PTX3 promoter, mediated the action of inflammatory transcription factors; and enhancer 2, encompassing PTX3 second exon, was implicated in pre-initiation complex assembly. Polycomb repressive complex 2 silenced these regulatory elements and the promoter in basal condition. Enhancer 1 was epigenetically inactivated in early colorectal cancer (CRC) stages, while the promoter and enhancer 2 showed increasingly DNA methylation during CRC progression from adenomas to stage II and III CRC. Inhibition of DNA methylation rescued PTX3 expression in CRC. Finally, enhancer 1 acquired the binding of STAT3 in stage I CRC, and inhibition of STAT3 phosphorylation restored PTX3 activity and decreased enhancer 1 methylation. Thus, the expression of PTX3 is under the control of two enhancers, which emerge as important fine regulators of PTX3 expression in inflammation and cancer.

Interplay between Myeloid Cells and Humoral Innate Immunity.

The innate immune system represents the first line of defense against pathogens and comprises both a cellular and a humoral arm. Fluid-phase pattern recognition molecules (PRMs), which include collectins, ficolins, and pentraxins, are key components of the humoral arm of innate immunity and are expressed by a variety of cells, including myeloid, epithelial, and endothelial cells, mainly in response to infectious and inflammatory conditions. Soluble PRMs share basic multifunctional properties including activation and regulation of the complement cascade, opsonization of pathogens and apoptotic cells, regulation of leukocyte extravasation, and fine-tuning of inflammation. Therefore, soluble PRMs are part of the immune response and retain antibody-like effector functions. Here, we will review the expression and general function of soluble PRMs, focusing our attention on the long pentraxin PTX3.

Pentraxin 3 As a Novel Diagnostic and Prognostic Biomarker for Acute GvHD and Fungal Infections in Adult Allogeneic HSCT Recipients

BACKGROUND:Pentraxin 3 (PTX3) is an essential component of the humoral arm of innate immunity, involved in controlling infections and modulating inflammation, and acting as a new prognostic and diagnostic biomarker in these conditions. PTX3 has been recently recognized as an extrinsic oncosuppressor in cancer; its role in hematological malignancies and allogeneic hematopoietic stem cell transplantation (allo-HSCT) is under investigation in both pediatric and adult settings.METHODS:From September 2012 we have conducted a prospective observational study to address the role of PTX3 in 35 adult patients affected by newly diagnosed AML (n=27) or ALL (8), and 73 adult pts who received allo-HSCT for acute leukemia. Stem cell donors were haploidentical (n=45), sibling (n=14), unrelated (n=14). Serial peripheral blood (PB) and bone marrow (BM) samples were collected from all patients. Time-points of sampling for leukemia patients included: diagnosis, relapse, any cycle of chemotherapy (CT; before starting and first day after the end), evaluation of treatment response (including BM), fever (first episode, or clinical suspicion of fungal infection). Samples from allo-HSCT patients were collected as following: before HSCT; at HSCT (day 0); day +7, day +14, 1 month (including BM), 2 months (including BM), 3 months (including BM) and 6 months (including BM) after HSCT; fever (first episode, or clinical suspicion of fungal infection); acute GvHD requiring systemic therapy (at onset or before starting a second line treatment, day+7 of treatment, then weekly during immunosuppressive therapy for 6 weeks). PTX3 level detection was performed with sandwich ELISA (detection limit 0.1 ng/ml).RESULTS:Firstly we analyzed the group of leukemia patients. Although PTX3 levels on PB at leukemia diagnosis were not influenced by patients (age, sex) or disease characteristics (type of leukemia, BM and PB blasts), they correlated with white blood cell counts (p=0,03). No statistical difference was found matching PTX3 levels at diagnosis with disease relapse or overall survival (OS). We did not observe any correlation between PTX3 levels before starting CT and response to treatment.When we moved to examine allo-HSCT patients, we observed an important difference in PTX3 levels on PB at day 0 among patients treated with treosulfan or busulfan-based conditioning (p=0,027). We found a trend towards an increase of PTX3 levels for patients who developed a subsequent GvHD at day +7, and for patients who received ATG instead of PT-Cy at day +14 (p =0,06 for both of them).Moreover, we evaluated 38 events of acute GvHD. Interestingly, PTX3 levels on PB at GvHD onset predict a subsequent evolution to chronic GvHD (p=0,02), also confirmed by ROC analysis (AUC 0.786) which allowed us to identify a threshold of 58 ng/ml (sens 75%, spec 85%). At day +7 from the start of therapy, PTX3 levels were correlated directly with steroid-refractory GvHD (p=0,004) and reflare (p=0,024), and inversely with GvHD resolution (p=0,003). Concomitantly, the ROC analysis identified a threshold of 18 ng/ml as predictor for steroid-resistance (AUC 0,91; sens 75%, spec 85%) and GvHD resolution (AUC 0,848; sens 70%, spec 85%).Finally, we reported 142 infectious events. No difference in PTX3 levels was reported for first and subsequent episodes, or with bloodstream infections. Importantly, in presence of invasive fungal infection (IFI), the levels of PTX3 were significantly increased (p=0,016).CONCLUSIONS:PTX3 is an early biomarker for major transplant-related complications, as IFI and acute GvHD. This study suggests that PTX3 is able to predict GvHD resolution and the risk of subsequent chronic GVHD development; moreover PTX3 predicts steroid-refractory GvHD, offering a new tool in pindividualized clinical management. DisclosuresCiceri:MolMed SpA: Consultancy.

An acidic microenvironment sets the humoral pattern recognition molecule PTX3 in a tissue repair mode

Pentraxin 3 (PTX3) is a fluid-phase pattern recognition molecule and a key component of the humoral arm of innate immunity. In four different models of tissue damage in mice, PTX3 deficiency was associated with increased fibrin deposition and persistence, and thicker clots, followed by increased collagen deposition, when compared with controls. Ptx3-deficient macrophages showed defective pericellular fibrinolysis in vitro. PTX3-bound fibrinogen/fibrin and plasminogen at acidic pH and increased plasmin-mediated fibrinolysis. The second exon-encoded N-terminal domain of PTX3 recapitulated the activity of the intact molecule. Thus, a prototypic component of humoral innate immunity, PTX3, plays a nonredundant role in the orchestration of tissue repair and remodeling. Tissue acidification resulting from metabolic adaptation during tissue repair sets PTX3 in a tissue remodeling and repair mode, suggesting that matrix and microbial recognition are common, ancestral features of the humoral arm of innate immunity.

Drosophila blood cells and their role in immune responses.

Drosophilamelanogaster has been extensively used to study the humoral arm of innate immunity because of the developmental and functional parallels with mammalian innate immunity. However, the fly cellular response to infection is far less understood. Investigative work on Drosophila haemocytes, the immunosurveillance cells of the insect, has revealed that they fulfil roles similar to mammalian monocytes and macrophages. They respond to wound signals and orchestrate the coagulation response. In addition, they phagocytose and encapsulate invading pathogens, and clear up apoptotic bodies controlling inflammation. This review briefly describes the Drosophila haematopoietic system and discusses what is currently known about the contribution of haemocytes to the immune response upon infection and wounding, during all stages of development.

Recognition of Neisseria meningitidis by the long pentraxin PTX3 and its role as an endogenous adjuvant.

Long pentraxin 3 (PTX3) is a non-redundant component of the humoral arm of innate immunity. The present study was designed to investigate the interaction of PTX3 with Neisseria meningitidis. PTX3 bound acapsular meningococcus, Neisseria-derived outer membrane vesicles (OMV) and 3 selected meningococcal antigens (GNA0667, GNA1030 and GNA2091). PTX3-recognized microbial moieties are conserved structures which fulfil essential microbial functions. Ptx3-deficient mice had a lower antibody response in vaccination protocols with OMV and co-administration of PTX3 increased the antibody response, particularly in Ptx3-deficient mice. Administration of PTX3 reduced the bacterial load in infant rats challenged with Neisseria meningitidis. These results suggest that PTX3 recognizes a set of conserved structures from Neisseria meningitidis and acts as an amplifier/endogenous adjuvant of responses to this bacterium.

PTX3 Is an Extrinsic Oncosuppressor Regulating Complement-Dependent Inflammation in Cancer

PTX3 is an essential component of the humoral arm of innate immunity, playing a nonredundant role in resistance against selected microbes and in the regulation of inflammation. PTX3 activates and regulates the Complement cascade by interacting with C1q and with Factor H. PTX3 deficiency was associated with increased susceptibility to mesenchymal and epithelial carcinogenesis. Increased susceptibility of Ptx3(-/-) mice was associated with enhanced macrophage infiltration, cytokine production, angiogenesis, and Trp53 mutations. Correlative evidence, gene-targeted mice, and pharmacological blocking experiments indicated that PTX3 deficiency resulted in amplification of Complement activation, CCL2 production, and tumor-promoting macrophage recruitment. PTX3 expression was epigenetically regulated in selected human tumors (e.g., leiomyosarcomas and colorectal cancer) by methylation of the promoter region and of a putative enhancer. Thus, PTX3, an effector molecule belonging to the humoral arm of innate immunity, acts as an extrinsic oncosuppressor gene in mouse and man by regulating Complement-dependent, macrophage-sustained, tumor-promoting inflammation.

Extracellular pattern recognition molecules in health and diseases.

The initiation of innate immune response relies on the recognition of pathogen-associated molecular patterns by pattern recognition molecules (PRMs), including the cellular pattern recognition receptors and extracellular soluble PRMs. Pattern recognition receptors such as Toll-like receptors (TLRs), NOD-like receptors and RIG-I like receptors are well documented cell-associated PRMs that sense microbial components on the cell surface, in the cytoplasm or in the nucleus of immune or non-immune cells to initiate the innate response to eliminate the invading pathogens.1,2 However, there is limited evidence of an extracellular PRM-mediated innate response to disease. In response to pathogen invasion, humoral PRMs are rapidly produced by a variety of cells and tissues, most notably by innate immune cells such as neutrophils, dendritic cells and macrophages. Extracellular humoral PRMs can be divided into different molecular families, primarily including pentraxins,3 collectins and ficolins.4 Accumulating evidence indicates that extracellular PRMs are important components of the humoral arm of innate immunity. They are able to recognize a variety of pathogenic agents and eliminate them through shared common mechanisms including complement activation, opsonization, agglutination, neutralization and regulation of inflammation (Figure 1). Moreover, extracellular PRMs also interact with cellular TLRs and regulate their function, jointly contributing to the recognition of microbial patterns and modulation of the innate immune responses.5,6,7,8

The Humoral Pattern Recognition Molecule PTX3 Is a Key Component of Innate Immunity against Urinary Tract Infection

Immunity in the urinary tract has distinct and poorly understood pathophysiological characteristics and urinary tract infections (UTIs) are important causes of morbidity and mortality. We investigated the role of the soluble pattern recognition molecule pentraxin 3 (PTX3), a key component of the humoral arm of innate immunity, in UTIs. PTX3-deficient mice showed defective control of UTIs and exacerbated inflammation. Expression of PTX3 was induced in uroepithelial cells by uropathogenic Escherichia coli (UPEC) in a Toll-like receptor 4 (TLR4)- and MyD88-dependent manner. PTX3 enhanced UPEC phagocytosis and phagosome maturation by neutrophils. PTX3 was detected in urine of UTI patients and amounts correlated with disease severity. In cohorts of UTI-prone patients, PTX3 gene polymorphisms correlated with susceptibility to acute pyelonephritis and cystitis. These results suggest that PTX3 is an essential component of innate resistance against UTIs. Thus, the cellular and humoral arms of innate immunity exert complementary functions in mediating resistance against UTIs.