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Iron overload remains a major cause of morbidity and mortality among β-thalassemia major (β-TM) patients. Iron regulatory proteins and their genetic variants together with changes in hepcidin levels in thalassemic patients could affect the disease manifestations. This work aimed to study genetic variations of ferroportin-1 (FPN1-8CG), Transmembrane Serine Protease 6 (TMPRSS6 rs855791) and hemojuvelin (HJV I222N and G320V) genes within a cohort of 97 β-TM Egyptian patients by Polymerase chain reaction Restriction Fragment Length Polymorphism (PCR-RFLP) in comparison to fifty normal control subjects. Among β-TM patients; the CG variant of FPN1 was significantly higher, while the TT and TC variants of TMPRSS6 were significantly lower in comparison to controls. Liver Iron Concentration (LIC) was significantly higher among β-TM patients harboring the FPN1 (GG) genotype and we found that FPN1gene mutation acts as independent predictor of MRI LIC (p = 0.011), Pulmonary artery pressure (PAP) was significantly higher in patients harboring the mutant FPN1 (GG and CG) genotypes (p value 0.04). β-TM patients having the HJV I222N (AA) genotype were having significantly higher cardiac iron overload (p value = 0.026). The studied genetic variants of iron regulatory proteins could alter the manifestations of iron overload thus resulting in different clinical phenotypes of thalassemic patients, these findings need to be confirmed by larger cohorts of patients with longer follow-up periods., Supplementary Information: The online version contains supplementary material available at 10.1007/s12288-022-01580-8., Competing Interests: Conflict of InterestAll authors declare no conflict of interest.Conflicts of interest/Competing InterestsThe authors declare no conflict of interests.Conflict of Interest:All Authors declare that they have no conflict of interest. The manuscript has not been submitted elsewhere nor previously published. All authors have contributed to the manuscript in significant ways, have reviewed and agreed upon the manuscript content., (© The Author(s) 2022.)

Introduction: Residual patent ductus arteriosus (rPDAs) can occur following surgical or transcatheter treatment, and are indicated for closure because of the risks of infective endarteritis and hemolysis in addition to the hemodynamic effect of the residual left-to-right shunt., Methods: This retrospective descriptive study describes our experience at two Egyptian centers (Cairo University Children's Hospital & Tanta University Hospital) with transcatheter treatment of rPDAs, from January 2009 to October 2017., Results: Twenty cases were treated: 17/20 postsurgical and 3/20 post-transcatheter, at a mean period of 13.4 ± 9.3 months from the initial procedure. The median rPDA size was 2 mm (range2-3.5 mm). Most common ductal anatomy was the conical shape. All rPDAs were successfully closed with either coils (13/20) or devices (6/20), except one case where the residual flow was within the device mesh material. Coils could be deployed from the antegrade or the retrograde approaches although the latter was associated with a higher incidence of late shunt occlusion. One case with a malpositioned device required simultaneous device and LPA stent deployment., Conclusion: Transcatheter closure of rPDAs is feasible in most cases, but may be technically challenging., (© 2019 Wiley Periodicals, Inc.)

Cell damage and death releases alarmins, self-derived immunomodulatory molecules that recruit and activate the immune system. Unfortunately, numerous processes critical to the transplantation of allogeneic materials result in the destruction of donor and recipient cells and may trigger alarmin release. Alarmins, often described as damage-associated molecular patterns, together with exogenous pathogen-associated molecular patterns, are potent orchestrators of immune responses; however, the precise role that alarmins play in alloimmune responses remains relatively undefined. We examined evolving concepts regarding how alarmins affect solid organ and allogeneic hematopoietic cell transplantation outcomes and the mechanisms by which self molecules are released. We describe how, once released, alarmins may act alone or in conjunction with nonself materials to contribute to cytokine networks controlling alloimmune responses and their intensity. It is becoming recognized that this class of molecules has pleotropic functions, and certain alarmins can promote both inflammatory and regulatory responses in transplant models. Emerging evidence indicates that alarmins and their receptors may be promising transplantation biomarkers. Developing the therapeutic ability to support alarmin regulatory mechanisms and the predictive value of alarmin pathway biomarkers for early intervention may provide opportunities to benefit graft recipients., Competing Interests: The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation., (© Copyright 2016 The American Society of Transplantation and the American Society of Transplant Surgeons.)

During allogeneic hematopoietic cell transplantation (alloHCT), nonhematopoietic cell interleukin-33 (IL-33) is augmented and released by recipient conditioning to promote type 1 alloimmunity and lethal acute graft-versus-host disease (GVHD). Yet, IL-33 is highly pleiotropic and exhibits potent immunoregulatory properties in the absence of coincident proinflammatory stimuli. We tested whether peri-alloHCT IL-33 delivery can protect against development of GVHD by augmenting IL-33-associated regulatory mechanisms. IL-33 administration augmented the frequency of regulatory T cells (Tregs) expressing the IL-33 receptor, suppression of tumorigenicity-2 (ST2), which persist following total body irradiation. ST2 expression is not exclusive to Tregs and IL-33 expands innate immune cells with regulatory or reparative properties. However, selective depletion of recipient Foxp3(+) cells concurrent with peri-alloHCT IL-33 administration accelerated acute GVHD lethality. IL-33-expanded Tregs protected recipients from GVHD by controlling macrophage activation and preventing accumulation of effector T cells in GVHD-target tissue. IL-33 stimulation of ST2 on Tregs activates p38 MAPK, which drives expansion of the ST2(+) Treg subset. Associated mechanistic studies revealed that proliferating Tregs exhibit IL-33-independent upregulation of ST2 and the adoptive transfer of st2(+) but not st2(-) Tregs mediated GVHD protection. In total, these data demonstrate the protective capacity of peri-alloHCT administration of IL-33 and IL-33-responsive Tregs in mouse models of acute GVHD. These findings provide strong support that the immunoregulatory relationship between IL-33 and Tregs can be harnessed therapeutically to prevent GVHD after alloHCT for treatment of malignancy or as a means for tolerance induction in solid organ transplantation., (© 2016 by The American Society of Hematology.)

Thymic-derived, regulatory T cells (Treg) represent a subset of CD4(+) T cells that are required for normal immune homeostasis and suppression of unwanted responses against self-antigens (Ags) that prevent autoimmunity. Their role as immune regulators and potent ability to suppress T cell responses has been the focus of intense investigations aimed at utilizing these cells therapeutically, particularly in the settings of autoimmunity and transplantation. Many methods for expanding Treg have been described; however, efforts to generate large numbers of Treg for use in vivo often compromise their suppressor function or rely on the induction of Treg rather than their expansion. Our recent studies have focused on the barrier tissue-derived cytokine IL-33, a recently described IL-1 family member. IL-33 has emerged as a multifunctional protein, with reported roles in driving potent Type 1 and Type 2 immunity, as well as facilitating profound Treg expansion in vitro and in vivo. IL-33-expanded Treg express the IL-33 receptor (R) ST2, and express classical markers associated with Treg phenotype and suppressor function. They suppress both CD4(+) and CD8(+) T cell proliferation and effector functions in vitro, and Treg expressing ST2 have been identified as important regulators of detrimental immune responses in vivo. In the present chapter, we detail methods for expanding significant numbers of Treg using IL-33 both in vitro and in vivo that may potentially be used to promote/maintain organ transplant tolerance or suppress autoimmunity.

Interleukin (IL)-33 binding to the receptor suppression of tumorigenicity 2 (ST2) produces pro-inflammatory and anti-inflammatory effects. Increased levels of soluble ST2 (sST2) are a biomarker for steroid-refractory graft-versus-host disease (GVHD) and mortality. However, whether sST2 has a role as an immune modulator or only as a biomarker during GVHD was unclear. We show increased IL-33 production by nonhematopoietic cells in the gastrointestinal (GI) tract in mice post-conditioning and patients during GVHD. Exogenous IL-33 administration during the peak inflammatory response worsened GVHD. Conversely, GVHD lethality and tumor necrosis factor-α production was significantly reduced in il33(-/-) recipients. ST2 was upregulated on murine and human alloreactive T cells and sST2 increased as experimental GVHD progressed. Concordantly, st2(-/-) vs wild-type (WT) donor T cells had a marked reduction in GVHD lethality and GI histopathology. Alloantigen-induced IL-18 receptor upregulation was lower in st2(-/-) T cells, and linked to reduced interferon-γ production by st2(-/-) vs WT T cells during GVHD. Blockade of IL-33/ST2 interactions during allogeneic-hematopoietic cell transplantation by exogenous ST2-Fc infusions had a marked reduction in GVHD lethality, indicating a role of ST2 as a decoy receptor modulating GVHD. Together, these studies point to the IL-33/ST2 axis as a novel and potent target for GVHD therapy., (© 2015 by The American Society of Hematology.)

IL-33 is a recently characterized IL-1 family member that is proposed to function as an alarmin, or endogenous signal of cellular damage, as well as act as a pleiotropic cytokine. The ability of IL-33 to potentiate both Th1 and Th2 immunity supports its role in pathogen clearance and disease immunopathology. Yet, IL-33 restrains experimental colitis and transplant rejection by expanding regulatory T cells (Treg) via an undefined mechanism. We sought to determine the influence of IL-33 on hematopoietic cells that drives Treg expansion and underlies the therapeutic benefit of IL-33 administration. In this study, we identify a feedback loop in which conventional mouse CD11c(+) dendritic cells (DC) stimulated by IL-33 secrete IL-2 to selectively expand IL-33R(ST2(+))- suppressive CD4(+)Foxp3(+) Treg. Interestingly, this occurs in the absence of classical DC maturation, and DC-derived (innate) IL-2 increases ST2 expression on both DC and interacting Treg. ST2(+) Treg represent an activated subset of Foxp3(+) cells, demonstrated to be ICOS(high)CD44(high) compared with their ST2(-) counterparts. Furthermore, although studies have shown that IL-33-exposed DC promote Th2 responses, we reveal that ST2(+) DC are required for IL-33-mediated in vitro and in vivo Treg expansion. Thus, we have uncovered a relationship between IL-33 and innate IL-2 that promotes the selective expansion of ST2(+) Treg over non-Treg. These findings identify a novel regulatory pathway driven by IL-33 in immune cells that may be harnessed for therapeutic benefit or for robust expansion of Treg in vitro and in vivo., (Copyright © 2014 by The American Association of Immunologists, Inc.)

Liver interstitial dendritic cells (DC) have been implicated in immune regulation and tolerance induction. We found that the transmembrane immuno-adaptor DNAX-activating protein of 12 kDa (DAP12) negatively regulated conventional liver myeloid (m) DC maturation and their in vivo migratory and T cell allostimulatory ability. Livers were transplanted from C57BL/6(H2(b) ) (B6) WT or DAP12(-/-) mice into WT C3H (H2(k) ) recipients. Donor mDC (H2-K(b+) CD11c(+) ) were quantified in spleens by flow cytometry. Anti-donor T cell reactivity was evaluated by ex vivo carboxyfluorescein diacetate succinimidyl ester-mixed leukocyte reaction and delayed-type hypersensitivity responses, while T effector and regulatory T cells were determined by flow analysis. A threefold to fourfold increase in donor-derived DC was detected in spleens of DAP12(-/-) liver recipients compared with those given WT grafts. Moreover, pro-inflammatory cytokine gene expression in the graft, interferon gamma (IFNγ) production by graft-infiltrating CD8(+) T cells and systemic levels of IFNγ were all elevated significantly in DAP12(-/-) liver recipients. DAP12(-/-) grafts also exhibited reduced incidences of CD4(+) Foxp3(+) cells and enhanced CD8(+) T cell IFNγ secretion in response to donor antigen challenge. Unlike WT grafts, DAP12(-/-) livers failed to induce tolerance and were rejected acutely. Thus, DAP12 expression in liver grafts regulates donor mDC migration to host lymphoid tissue, alloreactive T cell responses and transplant tolerance., (© Copyright 2014 The American Society of Transplantation and the American Society of Transplant Surgeons.)

The Flt3-Flt3 ligand (Flt3L) pathway is critically involved in the differentiation and homeostasis of myeloid cells, including dendritic cells (DC); however, its role in the expansion and function of myeloid-derived suppressor cells (MDSC) has not been determined. In this article, we describe the ability of Flt3L to expand and activate murine MDSC capable of suppressing allograft rejection upon adoptive transfer. Although Flt3L expands and augments the stimulatory capacity of myeloid DC, MDSC expanded by Flt3L have increased suppressive activity. Although STAT3 is considered the central transcription factor for MDSC expansion, inhibition and genetic ablation of STAT3 did not block, but rather augmented, Flt3L-mediated MDSC expansion. MDSC suppressive function, preserved when STAT3 inhibition was removed, was reduced by genetic STAT3 deletion. Both STAT3 inhibition and deletion reduced Flt3L-mediated DC expansion, signifying that STAT3 had reciprocal effects on suppressive MDSC and immunostimulatory DC expansion. Together, these findings enhance our understanding of the immunomodulatory properties of Flt3L.

An inverted Edwards SAPIEN 23 mm valve was implanted in a 14-year-old patient with Ebstein's anomaly who received a Medtronic Mosaic 25 mm valve 8 years earlier and presented with significant progressive symptoms related to severe valvular regurgitation and moderate stenosis. The procedure was performed via the femoral vein using the RetroFlex 3 system and predilatation of the tricuspid valve, under transesophageal echocardiographic guidance. The patient had an immediate drop in right atrial and trans-tricuspid pressures with mild regurgitation, and had stable results on short-term follow-up.

Mammalian target of rapamycin (mTOR) is an important, yet poorly understood integrative kinase that regulates immune cell function. mTOR functions in 2 independent complexes: mTOR complex (mTORC) 1 and 2. The immunosuppressant rapamycin (RAPA) inhibits mTORC1 but not mTORC2 and causes a paradoxical reduction in anti-inflammatory interleukin (IL) 10 and B7-homolog 1 (B7-H1) expression by dendritic cells (DCs). Using catalytic mTOR inhibitors and DCs lacking mTORC2, we show that restraint of signal transducer and activator of transcription 3-mediated IL-10 and B7-H1 expression during DC maturation involves a RAPA-insensitive and mTORC2-independent mTOR mechanism. Relatedly, catalytic mTOR inhibition promotes B7-H1-dependent and IL-1β-dependent DC induction of regulatory T cells (Tregs). Thus, we define an immunoregulatory pathway in which RAPA-sensitive mTORC1 in DCs promotes effector T-cell expansion and RAPA-insensitive mTORC1 restrains T(reg) induction. These findings identify the first known RAPA-insensitive mTOR pathway that is not mediated solely by mTORC2 and have implications for the use of catalytic mTOR inhibitors in inflammatory disease settings.

Hepatic stellate cells (HSCs) are critical for hepatic wound repair and tissue remodeling. They also produce cytokines and chemokines that may contribute to the maintenance of hepatic immune homeostasis and the inherent tolerogenicity of the liver. The functional relationship between HSCs and the professional migratory APCs in the liver, that is, dendritic cells (DCs), has not been evaluated. In this article, we report that murine liver DCs colocalize with HSCs in vivo under normal, steady-state conditions, and cluster with HSCs in vitro. In vitro, HSCs secrete high levels of DC chemoattractants, such as MΙP-1α and MCP-1, as well as cytokines that modulate DC activation, including TNF-α, IL-6, and IL-1β. Culture of HSCs with conventional liver myeloid (m) DCs resulted in increased IL-6 and IL-10 secretion compared with that of either cell population alone. Coculture also resulted in enhanced expression of costimulatory (CD80, CD86) and coinhibitory (B7-H1) molecules on mDCs. HSC-induced mDC maturation required cell-cell contact and could be blocked, in part, by neutralizing MΙP-1α or MCP-1. HSC-induced mDC maturation was dependent on activation of STAT3 in mDCs and, in part, on HSC-secreted IL-6. Despite upregulation of costimulatory molecules, mDCs conditioned by HSCs demonstrated impaired ability to induce allogeneic T cell proliferation, which was independent of B7-H1, but dependent upon HSC-induced STAT3 activation and subsequent upregulation of IDO. In conclusion, by promoting IDO expression, HSCs may act as potent regulators of liver mDCs and function to maintain hepatic homeostasis and tolerogenicity.

Plasmacytoid dendritic cells (pDCs) are highly specialized APCs that, in addition to their well-recognized role in anti-viral immunity, also regulate immune responses. Liver-resident pDCs are considerably less immunostimulatory than those from secondary lymphoid tissues and are equipped to promote immune tolerance/regulation through various mechanisms. IL-27 is an IL-12 family cytokine that regulates the function of both APCs and T cells, although little is known about its role in pDC immunobiology. In this study, we show that mouse liver pDCs express higher levels of IL-27p28 and EBV-induced protein 3 (Ebi3) compared with those of splenic pDCs. Both populations of pDCs express the IL-27Rα/WSX-1; however, only liver pDCs significantly upregulate expression of the coregulatory molecule B7 homolog-1 (B7-H1) in response to IL-27. Inhibition of STAT3 activation completely abrogates IL-27-induced upregulation of B7-H1 expression on liver pDCs. Liver pDCs treated with IL-27 increase the percentage of CD4(+)Foxp3(+) T cells in MLR, which is dependent upon expression of B7-H1. pDCs from Ebi3-deficient mice lacking functional IL-27 show increased capacity to stimulate allogeneic T cell proliferation and IFN-γ production in MLR. Liver but not spleen pDCs suppress delayed-type hypersensitivity responses to OVA, an effect that is lost with Ebi3(-/-) and B7-H1(-/-) liver pDCs compared with wild-type liver pDCs. These data suggest that IL-27 signaling in pDCs promotes their immunoregulatory function and that IL-27 produced by pDCs contributes to their capacity to regulate immune responses in vitro and in vivo.

Plasmacytoid DC (pDC) are type-I IFN-producing cells known for their capacity to promote anti-viral innate and adaptive immune responses. Despite their potent anti-viral function, when compared with conventional DC, pDC exhibit poor immunostimulatory ability and their interaction with T cells often favors the generation of Treg. pDC are activated primarily in response to ssRNA and ssDNA through TLR7 and TLR9, respectively, but also through TLR-independent mechanisms. Non-lymphoid tissue pDC, such as those residing in the airways, gut, and liver, play a significant role in regulating mucosal immunity and are critical for the development of tolerance to inhaled or ingested antigens. Herein we discuss properties that define tolerogenic pDC and how their unique characteristics translate into an ability to regulate immunity and promote the development of tolerance. We cover the importance of pDC during intrathymic Treg development and the maintenance of peripheral tolerance, as well as their regulatory role in transplantation, autoimmunity, and cancer. We highlight recent findings regarding danger-associated molecular pattern and PAMP signaling in the regulation of pDC function, and how the ability of pDC to promote tolerance translates into the potential clinical applications of these cells as therapeutic targets to regulate immune reactivity.

Minimization of immunosuppression and donor-specific tolerance to MHC-mismatched organ grafts are important clinical goals. The therapeutic potential of regulatory T cells (Tregs) has been demonstrated, but conditions for optimizing their in vivo function posttransplant in nonlymphocyte-depleted hosts remain undefined. In this study, we address mechanisms through which inhibition of the mammalian target of rapamycin (Rapa) synergizes with alloantigen-specific Treg (AAsTreg) to permit long-term, donor-specific heart graft survival in immunocompetent hosts. Crucially, immature allogeneic dendritic cells allowed AAsTreg selection in vitro, with minimal expansion of unwanted (Th17) cells. The rendered Treg potently inhibited T cell proliferation in an Ag-specific manner. However, these AAsTreg remained unable to control T cells stimulated by allogeneic mature dendritic cells, a phenomenon dependent on the release of proinflammatory cytokines. In vivo, Rapa administration reduced danger-associated IL-6 production, T cell proliferation, and graft infiltration. Based on these observations, AAsTreg were administered posttransplant (day 7) in combination with a short course of Rapa and rendered >80% long-term (>150 d) graft survival, a result superior to that achieved with polyclonal Treg. Moreover, graft protection was alloantigen-specific. Significantly, long-term graft survival was associated with alloreactive T cell anergy. These findings delineate combination of transient mammalian target of Rapa inhibition with appropriate AAsTreg selection as an effective approach to promote long-term organ graft survival.

Objective: To delineate the role of T-helper 2 (Th2) cytokines in the induction of trauma induced myeloid suppressor cells (TIMSC) and the regulation of nitric oxide production., Background: Trauma induces myeloid cells that express CD11b+/Gr1+ and arginase 1 and exhibit an immune suppressing activity. This article explores the mechanisms that induce TIMSC and the effects on nitric oxide production in response to endotoxin., Methods: TIMSC were studied in response to Th2 cytokines and a subsequent challenge to endotoxin. The role of Th2 cytokines was studied in STAT6-/- mice. Accumulation of TIMSC in spleens was studied using flow cytometry and immunhistochemistry. Plasma was recovered to measure accumulation of nitric oxide metabolites., Results: TIMSC accumulated in the spleen of injured mice and were particularly sensitive to IL-4 and IL-13 with large inductions of arginase activity. Significant blunting in both the accumulation of TIMSC in the spleen and induction of arginase 1 was observed in STAT6-/- mice after physical injury. Accumulation of nitric oxide metabolites to endotoxin was observed in STAT6-/- mice., Conclusion: This study shows that induction of CD11b+/Gr1+ cells after physical injury play an essential role in the regulation of nitric oxide production after a septic challenge. The accumulation and induction of arginase 1 in TIMSC is Th2 cytokine dependent. To our knowledge, the role of TIMSC in the regulation of nitric oxide is a novel finding. This observation adds to the possibility that TIMSC could play an important role in immunosuppression observed after physical injury.

The role of dendritic cells (DC) in transplantation is often overshadowed by the more prominent roles of T and B cells, which interact directly with and, in the absence of immunosuppressive therapy, destroy the allograft. It has become increasingly recognized, however, that these potent antigen-presenting cells exert control over the immune response and regulate the balance between tolerance and immunity to transplanted organs and tissues. The role that chemokines play in influencing DC function with impact on regulation of immune responses against the graft is only beginning to be understood. This article considers how the manipulation of DC trafficking during an alloimmune response can affect graft outcome.

T cell dysfunction that occurs after surgery or trauma is associated with a poor clinical outcome. We describe that myeloid suppressor cells expressing CD11b(+)/Gr-1(+) markers invade the spleen after traumatic stress and suppress T cell function through the production of arginase 1. We created a consistent model of traumatic stress in C57BL/6 mice to perform this work. A significant number of CD11b(+)/Gr-1(+) cells expressing arginase 1 accumulated in T cell zones around the germinal centers of the white pulp of the spleen within 6 h of trauma and lasted for at least 72 h. Increased arginase activity and arginase 1 expression, along with increased [(3)H]arginine uptake, l-arginine depletion, and l-ornithine accumulation in the culture medium, were observed exclusively in CD11b(+)/Gr-1(+) cells after traumatic stress. Flow cytometry revealed CD11b(+)/Gr-1(+) as a heterogeneous myeloid suppressor cell also expressing low levels of MHC class I and II, CD80, CD86, CD31, and others. When compared with controls, trauma-induced CD11b(+)/Gr-1(+) cells significantly inhibited CD3/CD28-mediated T cell proliferation, TCR zeta-chain expression, and IL-2 production. The suppressive effects by trauma CD11b(+)/Gr-1(+) cells were overcome with the arginase antagonist N-hydroxy-nor-l-arginine or extrasupplementation of medium with l-arginine. Poor Ag-presenting capacity of control and trauma-induced CD11b(+)/Gr-1(+) cells was detected in allogeneic murine leukocyte reaction. This study demonstrates that CD11b(+)/Gr-1(+) cells invade the spleen following traumatic stress and cause T cell dysfunction by an arginase-mediated mechanism, probably that of arginine depletion. Understanding the mechanism of immune suppression by these cells has important clinical implications in the treatment of immune dysfunction after trauma or surgery.

Speciation in animals is almost always envisioned as the split of an existing lineage into an ancestral and a derived species. An alternative speciation route is homoploid hybrid speciation in which two ancestral taxa give rise to a third, derived, species by hybridization without a change in chromosome number. Although theoretically possible it has been regarded as rare and hence of little importance in animals. On the basis of molecular and chromosomal evidence, hybridization is the best explanation for the origin of a handful of extant diploid bisexual animal taxa. Here we report the first case in which hybridization between two host-specific animals (tephritid fruitflies) is clearly associated with the shift to a new resource. Such a hybrid host shift presents an ecologically robust scenario for animal hybrid speciation because it offers a potential mechanism for reproductive isolation through differential adaptation to a new ecological niche. The necessary conditions for this mechanism of speciation are common in parasitic animals, which represent much of animal diversity. The frequency of homoploid hybrid speciation in animals may therefore be higher than previously assumed.