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.

Different coatings on magnetic nanoparticles dictate their degradation kinetics in vivo for 15 months after intravenous administration in mice.

BACKGROUND: The surface coating of iron oxide magnetic nanoparticle (MNPs) drives their intracellular trafficking and degradation in endolysosomes, as well as dictating other cellular outcomes. As such, we assessed whether MNP coatings might influence their biodistribution, their accumulation in certain organs and their turnover therein, processes that must be understood in vivo to optimize the design of nanoformulations for specific therapeutic/diagnostic needs. RESULTS: In this study, three different MNP coatings were analyzed, each conferring the identical 12 nm iron oxide cores with different physicochemical characteristics: 3-aminopropyl-triethoxysilane (APS), dextran (DEX), and dimercaptosuccinic acid (DMSA). When the biodistribution of these MNPs was analyzed in C57BL/6 mice, they all mainly accumulated in the spleen and liver one week after administration. The coating influenced the proportion of the MNPs in each organ, with more APS-MNPs accumulating in the spleen and more DMSA-MNPs accumulating in the liver, remaining there until they were fully degraded. The changes in the physicochemical properties of the MNPs (core size and magnetic properties) was also assessed during their intracellular degradation when internalized by two murine macrophage cell lines. The decrease in the size of the MNPs iron core was influenced by their coating and the organ in which they accumulated. Finally, MNP degradation was analyzed in the liver and spleen of C57BL/6 mice from 7 days to 15 months after the last intravenous MNP administration. CONCLUSIONS: The MNPs degraded at different rates depending on the organ and their coating, the former representing the feature that was fundamental in determining the time they persisted. In the liver, the rate of degradation was similar for all three coatings, and it was faster than in the spleen. This information regarding the influence of coatings on the in vivo degradation of MNPs will help to choose the best coating for each biomedical application depending on the specific clinical requirements.

Iron oxide and iron oxyhydroxide nanoparticles impair SARS-CoV-2 infection of cultured cells.

BACKGROUND: Coronaviruses usually cause mild respiratory disease in humans but as seen recently, some human coronaviruses can cause more severe diseases, such as the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the global spread of which has resulted in the ongoing coronavirus pandemic. RESULTS: In this study we analyzed the potential of using iron oxide nanoparticles (IONPs) coated with biocompatible molecules like dimercaptosuccinic acid (DMSA), 3-aminopropyl triethoxysilane (APS) or carboxydextran (FeraSpin™ R), as well as iron oxyhydroxide nanoparticles (IOHNPs) coated with sucrose (Venofer®), or iron salts (ferric ammonium citrate -FAC), to treat and/or prevent SARS-CoV-2 infection. At non-cytotoxic doses, IONPs and IOHNPs impaired virus replication and transcription, and the production of infectious viruses in vitro, either when the cells were treated prior to or after infection, although with different efficiencies. Moreover, our data suggest that SARS-CoV-2 infection affects the expression of genes involved in cellular iron metabolism. Furthermore, the treatment of cells with IONPs and IOHNPs affects oxidative stress and iron metabolism to different extents, likely influencing virus replication and production. Interestingly, some of the nanoparticles used in this work have already been approved for their use in humans as anti-anemic treatments, such as the IOHNP Venofer®, and as contrast agents for magnetic resonance imaging in small animals like mice, such as the FeraSpin™ R IONP. CONCLUSIONS: Therefore, our results suggest that IONPs and IOHNPs may be repurposed to be used as prophylactic or therapeutic treatments in order to combat SARS-CoV-2 infection.

Magnetic targeting of adoptively transferred tumour-specific nanoparticle-loaded CD8+ T cells does not improve their tumour infiltration in a mouse model of cancer but promotes the retention of these cells in tumour-draining lymph nodes.

BACKGROUND: Adoptive T cell-transfer (ATC) therapy is a highly promising cancer-treatment approach. However, in vivo-administered T cells tend to disperse, with only a small proportion reaching the tumour. To remedy this, magnetic targeting of T cells has been recently explored. Magnetic nanoparticles (MNPs) functionalised with antibodies were attached to effector T cells and magnetically recruited to tumour sites under MRI guidance. In this study, we investigated whether 3-aminopropyl-triethoxysilane (APS)-coated MNPs directly attached to CD8+ T cell membranes could also magnetically target and accumulate tumour-specific CD8+ T cells in solid tumours using an external magnetic field (EMF). As it has been shown that T cells associated with APS-coated MNPs are retained in lymph nodes (LNs), and tumour-draining LNs are the most common sites of solid-tumour metastases, we further evaluated whether magnetic targeting of APS-MNP-loaded CD8+ T cells could cause them to accumulate in tumour-draining LNs. RESULTS: First, we show that antigen-specific CD8+ T cells preserve their antitumor activity in vitro when associated with APS-MNPs. Next, we demonstrate that the application of a magnetic field enhanced the retention of APS-MNP-loaded OT-I CD8+ T cells under flow conditions in vitro. Using a syngeneic mouse model, we found similar numbers of APS-MNP-loaded OT-I CD8+ T cells and OT-I CD8+ T cells infiltrating the tumour 14 days after cell transfer. However, when a magnet was placed near the tumour during the transfer of tumour-specific APS-MNP-loaded CD8+ T cells to improve tumour infiltration, a reduced percentage of tumour-specific T cells was found infiltrating the tumour 14 days after cell transfer, which was reflected in a smaller reduction in tumour size compared to tumour-specific CD8+ T cells transferred with or without MNPs in the absence of a magnetic field. Nonetheless, magnet placement near the tumour site during cell transfer induced infiltration of activated tumour-specific CD8+ T cells in tumour-draining LNs, which remained 14 days after cell transfer. CONCLUSIONS: The use of an EMF to improve targeting of tumour-specific T cells modified with APS-MNPs reduced the percentage of these cells infiltrating the tumour, but promoted the retention and the persistence of these cells in the tumour-draining LNs.

T cells loaded with magnetic nanoparticles are retained in peripheral lymph nodes by the application of a magnetic field.

BACKGROUND: T lymphocytes are highly dynamic elements of the immune system with a tightly regulated migration. T cell-based transfer therapies are promising therapeutic approaches which in vivo efficacy is often limited by the small proportion of administered cells that reaches the region of interest. Manipulating T cell localisation to improve specific targeting will increase the effectiveness of these therapies. Nanotechnology has been successfully used for localized release of drugs and biomolecules. In particular, magnetic nanoparticles (MNPs) loaded with biomolecules can be specifically targeted to a location by an external magnetic field (EMF). The present work studies whether MNP-loaded T cells could be targeted and retained in vitro and in vivo at a site of interest with an EMF. RESULTS: T cells were unable to internalize the different MNPs used in this study, which remained in close association with the cell membrane. T cells loaded with an appropriate MNP concentration were attracted to an EMF and retained in an in vitro capillary flow-system. MNP-loaded T cells were also magnetically retained in the lymph nodes after adoptive transfer in in vivo models. This enhanced in vivo retention was in part due to the EMF application and to a reduced circulating cell speed within the organ. This combined use of MNPs and EMFs did not alter T cell viability or function. CONCLUSIONS: These studies reveal a promising approach to favour cell retention that could be implemented to improve cell-based therapy.

Polyethylenimine-coated superparamagnetic iron oxide nanoparticles impair in vitro and in vivo angiogenesis.

Endothelial cells are essential to tumor vascularization and impairing their activity can potentially limit tumor growth. Since polyethylenimine (PEI)-coated superparamagnetic iron oxide nanoparticles (SPIONs) are bioactive nanosystems that modulate inflammatory macrophage responses and limit tumor cell invasion, we evaluated their effects on endothelial cell angiogenesis. PEI-SPION triggered proinflammatory gene profiles in a murine endothelial cell line and in primary human umbilical cord vein endothelial cells (HUVECs). These nanoparticles impaired endothelial cell migration and inhibited HUVEC tube formation. Magnetically tumor-targeted PEI-SPIONs reduced tumor vessel numbers and promoted intratumor macrophage infiltration in a tumor xenograft model. PEI-SPION treatment impaired M2 macrophage-promoted tube formation and affected HUVEC cytoskeleton by limiting Src and Cortactin activation. These mechanisms could contribute to PEI-SPION in vitro and in vivo antiangiogenic potential. These data confirm that PEI-SPION administration and application of a localized magnetic field could offer an affordable anti-angiogenic anti-tumoral targeted treatment that would complement other therapies.

Inhibition of PI3Kδ reduces kidney infiltration by macrophages and ameliorates systemic lupus in the mouse.

Systemic lupus erythematosus (SLE) is a human chronic inflammatory disease generated and maintained throughout life by autoreactive T and B cells. Class I phosphoinositide 3-kinases (PI3K) are heterodimers composed of a regulatory and a catalytic subunit that catalyze phosphoinositide-3,4,5-P3 formation and regulate cell survival, migration, and division. Activity of the PI3Kδ isoform is enhanced in human SLE patient PBLs. In this study, we analyzed the effect of inhibiting PI3Kδ in MRL/lpr mice, a model of human SLE. We found that PI3Kδ inhibition ameliorated lupus progression. Treatment of these mice with a PI3Kδ inhibitor reduced the excessive numbers of CD4(+) effector/memory cells and B cells. In addition, this treatment reduced serum TNF-α levels and the number of macrophages infiltrating the kidney. Expression of inactive PI3Kδ, but not deletion of the other hematopoietic isoform PI3Kγ, reduced the ability of macrophages to cross the basement membrane, a process required to infiltrate the kidney, explaining MRL/lpr mice improvement by pharmacologic inhibition of PI3Kδ. The observations that p110δ inhibitor prolonged mouse life span, reduced disease symptoms, and showed no obvious secondary effects indicates that PI3Kδ is a promising target for SLE.

Superparamagnetic iron oxide nanoparticle uptake alters M2 macrophage phenotype, iron metabolism, migration and invasion.

Superparamagnetic iron oxide nanoparticles (SPIONs) have shown promise as contrast agents and nanocarriers for drug delivery. Their impact on M2-polarised macrophages has nonetheless not been well studied. Here we explored the effects of SPIONs coated with dimercaptosuccinic acid, aminopropyl silane or aminodextran in two M2 macrophage models (murine primary IL-4-activated bone marrow-derived macrophages and human M2-like differentiated THP-1 cells). All SPIONs were internalised and no cell toxicity was observed. SPION treatment produced reactive oxygen species and activated the extracellular signal-regulated kinase and AKT pathways. After 24-h SPION incubation, M2 macrophages switched their iron metabolism towards an iron-replete state. SPION treatment in both M2 macrophage models altered their M2 activation profiles, promoted IL-10 production, and stimulated protease-dependent invasion. These results highlight the need to evaluate the interactions between SPIONs and cells to take full advantage of the intrinsic properties of these nanoparticles in biological systems. FROM THE CLINICAL EDITOR: Superparamagnetic iron oxide nanoparticles (SPIONs) have been used as an MRI contrast agent in many experimental studies. The authors here investigated the effects of these nanoparticles on M2 macrophages after cellular uptake. The findings of cell activation further enhanced our current knowledge on the interaction of SPIONS with macrophages.

p38γ and p38δ kinases regulate the Toll-like receptor 4 (TLR4)-induced cytokine production by controlling ERK1/2 protein kinase pathway activation.

On the basis mainly of pharmacological experiments, the p38α MAP kinase isoform has been established as an important regulator of immune and inflammatory responses. However, the role of the related p38γ and p38δ kinases has remained unclear. Here, we show that deletion of p38γ and p38δ impaired the innate immune response to lipopolysaccharide (LPS), a Toll-like receptor 4 (TLR4) ligand, by blocking the extracellular signal-regulated kinase 1/2 (ERK1/2) activation in macrophages and dendritic cells. p38γ and p38δ were necessary to maintain steady-state levels of tumor progression locus 2 (TPL2), the MKK kinase that mediates ERK1/2 activation after TLR4 stimulation. TNFα, IL-1ß, and IL-10 production were reduced in LPS-stimulated macrophages from p38γ/δ-null mice, whereas IL-12 and IFNß production increased, in accordance with the known effects of TPL2/ERK1/2 signaling on the induction of these cytokines. Furthermore, p38γ/δ-deficient mice were less sensitive than controls to LPS-induced septic shock, showing lower TNFα and IL-1ß levels after challenge. Together, our results establish p38γ and p38δ as key components in innate immune responses.

DMSA-coated IONPs trigger oxidative stress, mitochondrial metabolic reprograming and changes in mitochondrial disposition, hindering cell cycle progression of cancer cells.

There is increasing interest in modulating the redox homeostasis of tumors since high levels of reactive oxygen species (ROS) make them more vulnerable to changes in these species. Nanomedicine offers promise in this context as such applications may provoke biological responses that induce ROS production. Indeed, iron oxide nanoparticles (IONPs) can induce ROS accumulation through the so-called Fenton reaction of iron, further augmenting the ROS in tumors and overloading the antioxidant system beyond its capacity, thereby driving oxidative stress to a level that is incompatible with cell survival. Here, three different coatings for IONPs were compared to assess their intrinsic capacity to induce ROS production in cells. Of these coatings, dimercaptosuccinic acid-coated IONPs (DMSA-NPs) provoked the strongest ROS production, which was associated with the ability to reprogram the metabolism of cancer cells. This latter phenomenon involved shutting-down oxidative phosphorylation (OXPHOS), shifting mitochondrial morphology towards a more elongated phenotype, reducing the total mitochondrial mass and ultimately, blocking cell proliferation by inducing G0/G1 cell cycle arrest. Consequently, the data obtained highlights the importance of studying the chemical properties of IONPs, presenting DMSA-NPs as a novel tool to induce oxidative stress in cancer cells and alter their cell fate.

Enhanced phosphoinositide 3-kinase δ activity is a frequent event in systemic lupus erythematosus that confers resistance to activation-induced T cell death.

Systemic lupus erythematosus (SLE) is a human chronic inflammatory disease caused by the action of autoreactive T and B cells. Class I phosphoinositide-3-kinases (PI3K) are enzymes that trigger formation of 3-poly-phosphoinositides that induce cell survival. Enhanced PI3K activation is a frequent event in human cancer. Nonetheless, in a genetic model with enhanced activation of class I(A) PI3K in T cells, mice show a greater tumor index but die of a lupus-like disease. In this study, we studied the potential PI3K involvement in human SLE. The PI3K pathway was frequently activated in SLE patient PBMC and T cells (∼70% of cases), more markedly in active disease phases. We examined the mechanism for PI3K pathway activation and found enhanced activation of PI3Kδ in SLE peripheral blood T cells. The magnitude of PI3K pathway activation in patients paralleled activated/memory T cell accumulation. We examined potential tolerance mechanisms affected by increased PI3K activity; SLE patients showed reduced activation-induced cell death of activated/memory T cells. Moreover, the defective activation-induced cell death in SLE T cells was corrected after reduction of PI3Kδ activity, suggesting that PI3Kδ contributes to induction of enhanced SLE memory T cell survival. These observations point to PI3Kδ as a target of clinical interest for SLE.

Ral GTPases regulate cell-mediated cytotoxicity in NK cells.

NK cells are key components of the immune response to virally infected and tumor cells. Recognition of target cells initiates a series of events in NK cells that culminates in target destruction via directed secretion of lytic granules. Ral proteins are members of the Ras superfamily of small GTPases; they regulate vesicular trafficking and polarized granule secretion in several cell types. In this study, we address the role of Ral GTPases in cell-mediated cytotoxicity. Using a human NK cell line and human primary NK cells, we show that both Ral isoforms, RalA and RalB, are activated rapidly after target cell recognition. Furthermore, silencing of RalA and RalB impaired NK cell cytotoxicity. RalA regulated granule polarization toward the immunological synapse and the subsequent process of degranulation, whereas RalB regulated degranulation but not polarization of lytic granules. Analysis of the molecular mechanism indicated that Ral activation in NK cells leads to assembly of the exocyst, a protein complex involved in polarized secretion. This assembly is required for degranulation, as interference with expression of the exocyst component Sec5 led to reduced degranulation and impaired cytotoxicity in NK cells. Our results thus identify a role for Ral in cell-mediated cytotoxicity, implicating these GTPases in lymphocyte function.

Interaction of Iron Oxide Nanoparticles with Macrophages Is Influenced Distinctly by "Self" and "Non-Self" Biological Identities.

Upon contact with biological fluids like serum, a protein corona (PC) complex forms on iron oxide nanoparticles (IONPs) in physiological environments and the proteins it contains influence how IONPs act in biological systems. Although the biological identity of PC-IONP complexes has often been studied in vitro and in vivo, there have been inconsistent results due to the differences in the animal of origin, the type of biological fluid, and the physicochemical properties of the IONPs. Here, we identified differences in the PC composition when it was derived from the sera of three species (bovine, murine, or human) and deposited on IONPs with similar core diameters but with different coatings [dimercaptosuccinic acid (DMSA), dextran (DEX), or 3-aminopropyl triethoxysilane (APS)], and we assessed how these differences influenced their effects on macrophages. We performed a comparative proteomic analysis to identify common proteins from the three sera that adsorb to each IONP coating and the 10 most strongly represented proteins in PCs. We demonstrated that the PC composition is dependent on the origin of the serum rather than the nature of the coating. The PC composition critically affects the interaction of IONPs with macrophages in self- or non-self identity models, influencing the activation and polarization of macrophages. However, such effects were more consistent for DMSA-IONPs. As such, a self biological identity of IONPs promotes the activation and M2 polarization of murine macrophages, while a non-self biological identity favors M1 polarization, producing larger quantities of ROS. In a human context, we observed the opposite effect, whereby a self biological identity of DMSA-IONPs promotes a mixed M1/M2 polarization with an increase in ROS production. Conversely, a non-self biological identity of IONPs provides nanoparticles with a stealthy character as no clear effects on human macrophages were evident. Thus, the biological identity of IONPs profoundly affects their interaction with macrophages, ultimately defining their biological impact on the immune system.

Cubic Mesocrystal Magnetic Iron Oxide Nanoparticle Formation by Oriented Aggregation of Cubes in Organic Media: A Rational Design to Enhance the Magnetic Hyperthermia Efficiency.

Magnetic iron oxide mesocrystals have been reported to exhibit collective magnetic properties and consequently enhanced heating capabilities under alternating magnetic fields. However, there is no universal mechanism to fully explain the formation pathway that determines the particle diameter, crystal size, and shape of these mesocrystals and their evolution along with the reaction. In this work, we have analyzed the formation of cubic magnetic iron oxide mesocrystals by thermal decomposition in organic media. We have observed that a nonclassical pathway leads to mesocrystals via the attachment of crystallographically aligned primary cubic particles and grows through sintering with time to achieve a sizable single crystal. In this case, the solvent 1-octadecene and the surfactant agent biphenyl-4-carboxylic acid seem to be the key parameters to form cubic mesocrystals as intermediates of the reaction in the presence of oleic acid. Interestingly, the magnetic properties and hyperthermia efficiency of the aqueous suspensions strongly depend on the degree of aggregation of the cores forming the final particle. The highest saturation magnetization and specific absorption rate values were found for the less aggregated mesocrystals. Thus, these cubic magnetic iron oxide mesocrystals stand out as an excellent alternative for biomedical applications with their enhanced magnetic properties.

PI3Kgamma inhibition blocks glomerulonephritis and extends lifespan in a mouse model of systemic lupus.

Systemic lupus erythematosus (SLE) is a chronic inflammatory disease generated by deregulation of T cell-mediated B-cell activation, which results in glomerulonephritis and renal failure. Disease is treated with immunosuppressants and cytostatic agents that have numerous side effects. Here we examine the use of inhibitors of phosphoinositide 3-kinase (PI3K) gamma, a lipid kinase that regulates inflammation, in the MRL-lpr mouse model of SLE. Treatment reduced glomerulonephritis and prolonged lifespan, suggesting that P13Kgamma may be a useful target in the treatment of chronic inflammation.

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.

The surface coating of iron oxide nanoparticles drives their intracellular trafficking and degradation in endolysosomes differently depending on the cell type.

Magnetic nanoparticles (MNPs) are potential theranostic tools that are biodegraded through different endocytic pathways. However, little is known about the endolysosomal network through which MNPs transit and the influence of the surface coating in this process. Here, we studied the intracellular transit of two MNPs with identical iron oxide core size but with two distinct coatings: 3-aminopropyl-trietoxysilane (APS) and dimercaptosuccinic acid (DMSA). Using endolysosomal markers and a high throughput analysis of the associated proteome, we tracked the MNPs intracellularly in two different mouse cell lines, RAW264.7 (macrophages) and Pan02 (tumor cells). We did not detect differences in the MNP trafficking kinetics nor in the MNP-containing endolysosome phenotype in Pan02 cells. Nonetheless, DMSA-MNPs transited at slower rate than APS-MNPs in macrophages as measured by MNP accumulation in Rab7+ endolysosomes. Macrophage DMSA-MNP-containing endolysosomes had a higher percentage of lytic enzymes and catalytic proteins than their APS-MNP counterparts, concomitantly with a V-type ATPase enrichment, suggesting an acidic nature. Consequently, more autophagic vesicles are induced by DMSA-MNPs in macrophages, enhancing the expression of iron metabolism-related genes and proteins. Therefore, unlike Pan02 cells, the MNP coating appears to influence the intracellular trafficking rate and the endolysosome nature in macrophages. These results highlight how the MNP coating can determine the nanoparticle intracellular fate and biodegradation in a cell-type bias.

Cytolytic granule polarization and degranulation controlled by different receptors in resting NK cells.

The relative contribution to cytotoxicity of each of the multiple NK cell activation receptors has been difficult to assess. Using Drosophila insect cells, which express ligands of human NK cell receptors, we show that target cell lysis by resting NK cells is controlled by different receptor signals for cytolytic granule polarization and degranulation. Intercellular adhesion molecule (ICAM)-1 on insect cells was sufficient to induce polarization of granules, but not degranulation, in resting NK cells. Conversely, engagement of the Fc receptor CD16 by rabbit IgG on insect cells induced degranulation without specific polarization. Lysis by resting NK cells occurred when polarization and degranulation were induced by the combined presence of ICAM-1 and IgG on insect cells. Engagement of receptor 2B4 by CD48 on insect cells induced weak polarization and no degranulation. However, coengagement of 2B4 and CD16 by their respective ligands resulted in granule polarization and cytotoxicity in the absence of leukocyte functional antigen-1-mediated adhesion to target cells. These data show that cytotoxicity by resting NK cells is controlled tightly by separate or cooperative signals from different receptors for granule polarization and degranulation.

p85beta phosphoinositide 3-kinase regulates CD28 coreceptor function.

CD28 is a receptor expressed on T cells that regulates their differentiation after antigen stimulation to long-term-survival memory T cells. CD28 enhances T-cell receptor signals and reduces expression of CBL ubiquitin ligases, which negatively control T-cell activation. In the absence of CD28 ligation during the primary stimulation, CBL levels remain high and T cells fail to mount an efficient secondary response. CD28 associates with p85alpha, one of the regulatory subunits of phosphoinositide-3-kinase (PI3K), but the relevance of this interaction is debated. We examined here the contribution of the other ubiquitous PI3K regulatory subunit, p85beta, in CD28 function. We describe that p85beta bound to CD28 and to CBL with greater affinity than p85alpha. Moreover, deletion of p85beta impaired CD28-induced intracellular events, including c-CBL and CBL-b down-regulation as well as PI3K pathway activation. This resulted in defective differentiation of activated T cells, which failed to exhibit an efficient secondary immune response. Considering that p85beta-deficient T cells fail in recall responses and that p85beta binds to and regulates CD28 signals, the presented observations suggest the involvement of p85beta in CD28-mediated activation and differentiation of antigen-stimulated T cells.

The Use of Iron Oxide Nanoparticles to Reprogram Macrophage Responses and the Immunological Tumor Microenvironment.

The synthesis and functionalization of iron oxide nanoparticles (IONPs) is versatile, which has enhanced the interest in studying them as theranostic agents over recent years. As IONPs begin to be used for different biomedical applications, it is important to know how they affect the immune system and its different cell types, especially their interaction with the macrophages that are involved in their clearance. How immune cells respond to therapeutic interventions can condition the systemic and local tissue response, and hence, the final therapeutic outcome. Thus, it is fundamental to understand the effects that IONPs have on the immune response, especially in cancer immunotherapy. The biological effects of IONPs may be the result of intrinsic features of their iron oxide core, inducing reactive oxygen species (ROS) and modulating intracellular redox and iron metabolism. Alternatively, their effects are driven by the nanoparticle coating, for example, through cell membrane receptor engagement. Indeed, exploiting these properties of IONPs could lead to the development of innovative therapies. In this review, after a presentation of the elements that make up the tumor immunological microenvironment, we will review and discuss what is currently known about the immunomodulatory mechanisms triggered by IONPs, mainly focusing on macrophage polarization and reprogramming. Consequently, we will discuss the implications of these findings in the context of plausible therapeutic scenarios for cancer immunotherapy.