Peripheral Innate Immune Cells Research Articles

Peripheral innate immunophenotype in neurodegenerative disease: blood-based profiles and links to survival.

The innate immune system plays an integral role in the progression of many neurodegenerative diseases. In addition to central innate immune cells (e.g., microglia), peripheral innate immune cells (e.g., blood monocytes, natural killer cells, and dendritic cells) may also differ in these conditions. However, the characterization of peripheral innate immune cell types across different neurodegenerative diseases remains incomplete. This study aimed to characterize peripheral innate immune profiles using flow cytometry for immunophenotyping of peripheral blood mononuclear cells in n = 148 people with Alzheimer's disease (AD), frontotemporal dementia (FTD), corticobasal syndrome (CBS), progressive supranuclear palsy (PSP), Lewy body dementia(LBD) as compared to n = 37 healthy controls. To compare groups, we used multivariate dissimilarity analysis and principal component analysis across 19 innate immune cell types. We identified pro-inflammatory profiles that significantly differ between patients with all-cause dementia and healthy controls, with some significant differences between patient groups. Regression analysis confirmed that time to death following the blood test correlated with the individuals' immune profile weighting, positively to TREM2+ and non-classical monocytes and negatively to classical monocytes. Taken together, these results describe transdiagnostic peripheral immune profiles and highlight the link between prognosis and the monocyte cellular subdivision and function (as measured by surface protein expression). The results suggest that blood-derived innate immune profiles can inform sub-populations of cells relevant for specific neurodegenerative diseases that are significantly linked to accelerated disease progression and worse survival outcomes across diagnoses. Blood-based innate immune profiles may contribute to enhanced precision medicine approaches in dementia, helping to identify and monitor therapeutic targets and stratify patients for candidate immunotherapies.

LRRK2 kinase activity restricts NRF2-dependent mitochondrial protection in microglia.

Mounting evidence supports a critical role for central nervous system (CNS) glial cells in neuroinflammation and neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's Disease (PD), Multiple Sclerosis (MS), as well as neurovascular ischemic stroke. Previously, we found that loss of the PD-associated gene leucine-rich repeat kinase 2 (Lrrk2) in macrophages, peripheral innate immune cells, induced mitochondrial stress and elevated basal expression of type I interferon (IFN) stimulated genes (ISGs) due to chronic mitochondrial DNA engagement with the cGAS/STING DNA sensing pathway. Here, we report that loss of LRRK2 results in a paradoxical response in microglial cells, a CNS-specific macrophage population. In primary murine microglia and microglial cell lines, loss of Lrrk2 reduces tonic IFN signaling leading to a reduction in ISG expression. Consistent with reduced type I IFN, mitochondria from Lrrk2 KO microglia are protected from stress and have elevated metabolism. These protective phenotypes involve upregulation of NRF2, an important transcription factor in the response to oxidative stress and are restricted by LRRK2 kinase activity. Collectively, these findings illustrate a dichotomous role for LRRK2 within different immune cell populations and give insight into the fundamental differences between immune regulation in the CNS and the periphery.

Visceral Adiposity and Neutralizing Antibody Expression: An Adult-Based Cross-Sectional Study.

Visceral adiposity is a significant risk factor for severe COVID-19. However, the impact of the Chinese visceral adiposity index (CVAI) on the efficacy of SARS-CoV-2 vaccines remains poorly understood. This study aims to explore the impact of CVAI on the production of neutralizing antibodies (NAb) in inactivated SARS-CoV-2 vaccines and the potential mechanism, thereby optimizing vaccination guidance. In this cross-sectional study, 206 health workers (completed two SARS-CoV-2 vaccination on February 8th and March 10th, 2021, respectively) were recruited. All baseline anthropometric parameters of the participants were collected, and venous blood samples were obtained 6 weeks later to measure peripheral innate immune cells, inflammatory cytokines, and NAb titers against SARS-CoV-2. CVAI were calculated according to the formula and divided participants into two groups depending on CVAI median. The median NAb titer among healthcare workers was 12.94 AU/mL, with an efficacy of 87.86% for the SARS-CoV-2 vaccine. NAb titers were lower in the CVAI dysfunction group than in the CVAI reference group (median: 11.40 AU/mL vs 15.57 AU/mL), the hsCRP levels (median: 0.50 mg/L vs 0.30 mg/L) and peripheral monocyte count (mean: 0.47 × 109/L vs 0.42 × 109/L) in the CVAI dysfunction group were higher than in the CVAI reference group. Additionally, CVAI showed positive correlations with hsCRP, monocytes, lymphocytes, and B-lymphocytes, and a negative correlation with NAb titers. CVAI may inhibit SARS-CoV-2 neutralizing antibody expression through inducing immune dysfunction and chronic inflammation. Thus, more attention should be paid to the vaccination for high CVAI population to improve the effectiveness of vaccination, which could provide more robust support for COVID-19 epidemic prevention and control.

Peripheral monocytes and neutrophils promote photoreceptor cell death in an experimental retinal detachment model

Photoreceptor cell death and immune cell infiltration are two major events that contribute to retinal degeneration. However, the relationship between these two events has not been well delineated, primarily because of an inadequate understanding of the immunological processes involved in photoreceptor degeneration, especially that of peripheral leukocytes that infiltrate the subretinal space and retinal tissues. In this work, we characterized the role of leukocyte infiltration within the detached retina. We observed that CD45+ CD11b+ Ly6G+ neutrophils and CD45+ CD11b+ Ly6G− Ly6C+ monocytes are the predominant peripheral immune cell populations that infiltrate the retinal and subretinal space after detachment. Selective depletion of monocytes or neutrophils using cell-specific targeting is neuroprotective for photoreceptors. These results indicate that peripheral innate immune cells contribute to photoreceptor degeneration, and targeting these immune cell populations could be therapeutic during retinal detachment.

Repeated social defeat stress leads to immunometabolic shifts in innate immune cells of the spleen

Psychosocial stress has been shown to prime peripheral innate immune cells, which take on hyper-inflammatory phenotypes and are implicated in depressive-like behavior in mouse models. However, the impact of stress on cellular metabolic states that are thought to fuel inflammatory phenotypes in immune cells are unknown. Using single cell RNA-sequencing, we investigated mRNA enrichment of immunometabolic pathways in innate immune cells of the spleen in mice subjected to repeated social defeat stress (RSDS) or no stress (NS). RSDS mice displayed a significant increase in the number of splenic macrophages and granulocytes (p < 0.05) compared to NS littermates. RSDS-upregulated genes in macrophages, monocytes, and granulocytes significantly enriched immunometabolic pathways thought to play a role in myeloid-driven inflammation (glycolysis, HIF-1 signaling, MTORC1 signaling) as well as pathways related to oxidative phosphorylation (OXPHOS) and oxidative stress (p < 0.05 and FDR<0.1). These results suggest that the metabolic enhancement reflected by upregulation of glycolytic and OXPHOS pathways may be important for cellular proliferation of splenic macrophages and granulocytes following repeated stress exposure. A better understanding of these intracellular metabolic mechanisms may ultimately help develop novel strategies to reverse the impact of stress and associated peripheral immune changes on the brain and behavior.

Propranolol treatment during repetitive mild traumatic brain injuries induces transcriptomic changes in the bone marrow of mice.

There are 1.5 million new mild traumatic brain injuries (mTBI) annually in the US, with many of the injured experiencing long-term consequences lasting months after the injury. Although the post injury mechanisms are not well understood, current knowledge indicates peripheral immune system activation as a causal link between mTBI and long-term side effects. Through a variety of mechanisms, peripheral innate immune cells are recruited to the CNS after TBI to repair and heal the injured tissue; however, the recruitment and activation of these cells leads to further inflammation. Emerging evidence suggests sympathetic nervous system (SNS) activity plays a substantial role in the recruitment of immune cells post injury. We sought to identify the peripheral innate immune response after repeated TBIs in addition to repurposing the nonselective beta blocker propranolol as a novel mTBI therapy to limit SNS activity and mTBI pathophysiology in the mouse. Mice underwent repetitive mTBI or sham injury followed by i.p. saline or propranolol. Isolated mRNA derived from femur bone marrow of mice was assayed for changes in gene expression at one day, one week, and four weeks using Nanostring nCounter® stem cell characterization panel. Differential gene expression analysis for bone marrow uncovered significant changes in many genes following drug alone, mTBI alone and drug combined with mTBI. Our data displays changes in mRNA at various timepoints, most pronounced in the mTBI propranolol group, suggesting a single dose propranolol injection as a viable future mTBI therapy in the acute setting.

The effects and potential of microglial polarization and crosstalk with other cells of the central nervous system in the treatment of Alzheimer's disease.

Microglia are resident immune cells in the central nervous system. During the pathogenesis of Alzheimer's disease, stimulatory factors continuously act on the microglia causing abnormal activation and unbalanced phenotypic changes; these events have become a significant and promising area of research. In this review, we summarize the effects of microglial polarization and crosstalk with other cells in the central nervous system in the treatment of Alzheimer's disease. Our literature search found that phenotypic changes occur continuously in Alzheimer's disease and that microglia exhibit extensive crosstalk with astrocytes, oligodendrocytes, neurons, and penetrated peripheral innate immune cells via specific signaling pathways and cytokines. Collectively, unlike previous efforts to modulate microglial phenotypes at a single level, targeting the phenotypes of microglia and the crosstalk with other cells in the central nervous system may be more effective in reducing inflammation in the central nervous system in Alzheimer's disease. This would establish a theoretical basis for reducing neuronal death from central nervous system inflammation and provide an appropriate environment to promote neuronal regeneration in the treatment of Alzheimer's disease.

The Innate and Adaptive Immune Cells in Alzheimer's and Parkinson's Diseases.

Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common neurodegenerative disorders of the central nervous system (CNS). Increasing evidence supports the view that dysfunction of innate immune cells initiated by accumulated and misfolded proteins plays essential roles in the pathogenesis and progression of these diseases. The TLR family was found to be involved in the regulation of microglial function in the pathogenesis and progression of AD or PD, making it as double-edged sword in these diseases. Altered function of peripheral innate immune cells was found in AD and PD and thus contributed to the development and progression of AD and PD. Alteration of different subsets of T cells was found in the peripheral blood and CNS in AD and PD. The CNS-infiltrating T cells can exert both neuroprotective and neurotoxic effects in the pathogenesis and progression. Here, we review recent evidences for the roles of innate and adaptive immune cells in the pathogenesis and progression of AD and PD.

Ginkgo Biloba Leaf Extract Improves an Innate Immune Response of Peripheral Blood Leukocytes of Alzheimer’s Disease Patients

Background: One of the main features of Alzheimer’s disease (AD) pathology is failure in innate immune response and chronic inflammation. Lack of effective AD treatment means that more attention is paid to alternative therapy and drugs of natural origin, such as extract of Ginkgo biloba (EGb). The purpose of this study was to investigate the effect of EGb on the mechanisms of innate immune response of peripheral blood leukocytes (PBLs) in AD patients. Methods: In AD patients and healthy-age matched controls, the effect of EGb on two of innate immune reactions, i.e., PBLs resistance to viral infection ex vivo and production of cytokines, namely TNF-α, IFN-γ, IL-1β, IL-10, IL-15, and IFN-α, were investigated. The influence of EGb on inflammatory-associated genes expression that regulate innate immune response to viral infection and cytokine production, namely IRF-3, IRF-7, tetherin, SOCS1, SOCS3, NFKB1, p65, and MxA was also examined. Results: A beneficial effect of EGb especially in AD women was observed. EGb decreased production of TNF-α, IFN-γ, and IL-10 and increased IL-15 and IL-1β. The effect was more pronouncement in AD group. EGb also downregulated expression of investigated genes. Conclusions: EGb may have an advantageous properties for health management in elderly and AD sufferers but especially in women with AD. Improving peripheral innate immune cells’ activity by adding EGb as accompanying treatment in AD may be, in the long term, a good course to modify the disease progression.

Anti-CD52 antibody treatment in murine experimental autoimmune encephalomyelitis induces dynamic and differential modulation of innate immune cells in peripheral immune and central nervous systems.

Anti‐CD52 antibody (anti‐CD52‐Ab) leads to a rapid depletion of T and B cells, followed by reconstitution of immune cells with tolerogenic characteristics. However, very little is known about its effect on innate immune cells. In this study, experimental autoimmune encephalomyelitis mice were administered murine anti‐CD52‐Ab to investigate its effect on dendritic cells and monocytes/macrophages in the periphery lymphoid organs and the central nervous system (CNS). Our data show that blood and splenic innate immune cells exhibited significantly increased expression of MHC‐II and costimulatory molecules, which was associated with increased capacity of activating antigen‐specific T cells, at first day but not three weeks after five daily treatment with anti‐CD52‐Ab in comparison with controls. In contrast to the periphery, microglia and infiltrating macrophages in the CNS exhibited reduced expression levels of MHC‐II and costimulatory molecules after antibody treatment at both time‐points investigated when compared to controls. Furthermore, the transit response of peripheral innate immune cells to anti‐CD52‐Ab treatment was also observed in the lymphocyte‐deficient SCID mice, suggesting the changes are not a direct consequence of the mass depletion of lymphocytes in the periphery. Our study demonstrates a dynamic and tissue‐specific modulation of the innate immune cells in their phenotype and function following the antibody treatment. The findings of differential modulation of the microglia and infiltrating macrophages in the CNS in comparison with the innate immune cells in the peripheral organs support the CNS‐specific beneficial effect of alemtuzumab treatment on inhibiting neuroinflammation in multiple sclerosis patients.

Regulation of the innate immune cells during pregnancy: An immune checkpoint perspective.

The foetus can be regarded as a half‐allograft implanted into the maternal body. In a successful pregnancy, the mother does not reject the foetus because of the immune tolerance mechanism at the maternal‐foetal interface. The innate immune cells are a large part of the decidual leukocytes contributing significantly to a successful pregnancy. Although the contributions have been recognized, their role in human pregnancy has not been completely elucidated. Additionally, the accumulated evidence demonstrates that the immune checkpoint molecules expressed on the immune cells are co‐inhibitory receptors regulating their activation and biological function. Therefore, it is critical to understand the immune microenvironment and explore the function of the innate immune cells during pregnancy. This review summarizes the classic immune checkpoints such as PD‐1, CTLA‐4 and some novel molecules recently identified, including TIM‐3, CD200, TIGIT and the Siglecs family on the decidual and peripheral innate immune cells during pregnancy. Furthermore, it emphasizes the role of the immune checkpoint molecules in pregnancy‐associated complications and reproductive immunotherapy.

Mast cells modulate early responses to Mycobacterium bovis Bacillus Calmette-Guerin by phagocytosis and formation of extracellular traps

The early interactions between the vaccine Mycobacterium bovis Bacillus Calmette Guerin (BCG) and host peripheral innate immune cells like Mast cells (MCs) may pave the way for generating appropriate protective innate and adaptive immune responses. Mice on administration of BCG by intratracheal instillation showed a massive increase in MC numbers in the infected lung. In vitro co-culture of BCG and rodent Rat Basophilic Leukaemia (RBL-2H3) MCs led to significant killing of BCG. RBL-2H3 MCs were able to phagocytose BCG, take up BCG-derived antigens by macropinocytosis, generate Reactive Oxygen Species (ROS) and degranulate. Further, a few MCs died and released MC extracellular traps (MCETs) having DNA, histones and tryptase to trap BCG. This study highlights the multi-pronged effector responses of MCs on encountering BCG. These responses or their evasion may lead to success or failure of BCG vaccine to provide long term immunity to infections.

Peripheral Myeloid Cell EP2 Activation Contributes to the Deleterious Consequences of Status Epilepticus.

A multidimensional inflammatory response ensues after status epilepticus (SE), driven partly by cyclooxygenase-2-mediated activation of prostaglandin EP2 receptors. The inflammatory response is typified by astrocytosis, microgliosis, erosion of the blood-brain barrier (BBB), formation of inflammatory cytokines, and brain infiltration of blood-borne monocytes. Our previous studies have shown that inhibition of monocyte brain invasion or systemic administration of an EP2 receptor antagonist relieves multiple deleterious consequences of SE. Here we identify those effects of EP2 antagonism that are reproduced by conditional ablation of EP2 receptors in immune myeloid cells and show that systemic EP2 antagonism blocks monocyte brain entry in male mice. The induction of hippocampal IL-6 after pilocarpine SE was nearly abolished in EP2 conditional KO mice. Serum albumin levels in the cortex, a measure of BBB breakdown, were significantly higher after SE in EP2-sufficient mice but not in EP2 conditional KOs. EP2 deficiency in innate immune cells accelerated the recovery from sickness behaviors following SE. Surprisingly, neurodegeneration was not alleviated in myeloid conditional KOs. Systemic EP2 antagonism prevented monocyte brain infiltration and provided broader rescue of SE-induced effects than myeloid EP2 ablation, including neuroprotection and broader suppression of inflammatory mediators. Reporter expression indicated that the cellular target of CD11b-driven Cre was circulating myeloid cells but, unexpectedly, not microglia. These findings indicate that activation of EP2 receptors on immune myeloid cells drives substantial deficits in behavior and disrupts the BBB after SE. The benefits of systemic EP2 antagonism can be attributed, in part, to blocking brain recruitment of blood-borne monocytes.SIGNIFICANCE STATEMENT Unabated seizures reduce quality of life, promote the development of epilepsy, and can be fatal. We previously identified activation of prostaglandin EP2 receptors as a driver of undesirable consequences of seizures. However, the relevant EP2-expressing cell types remain unclear. Here we identify peripheral innate immune cells as a driver of the EP2-related negative consequences of seizures. Removal of EP2 from peripheral immune cells was beneficial, abolishing production of a key inflammatory cytokine, accelerating weight regain, and limiting behavioral deficits. These findings provide evidence that EP2 engagement on peripheral immune and brain endothelia contributes to the deleterious effects of SE, and will assist in the development of beneficial therapies to enhance quality of life in individuals who suffer prolonged seizures.

Pseudoginsenoside-F11 ameliorates ischemic neuron injury by regulating the polarization of neutrophils and macrophages in vitro

Pseudoginsenoside-F11 (PF11), an ocotillol-type saponin, has neuroprotective effects on permanent and transient cerebral ischemia in rats by alleviating autophagic/lysosomal defects and repressing calcium overload, respectively. Ischemic stroke triggers peripheral innate immune cells, mainly neutrophils and macrophages, to infiltrate the damaged brain. The polarization of neutrophils and macrophages after cerebral ischemia is essential for post-stroke damage/recovery. However, it remains elusive whether PF11 ameliorates ischemic neuron injury by regulating the polarization of neutrophils and macrophages. The present study demonstrated for the first time that conditioned media from ischemic neurons induced neutrophils and macrophages to polarize into N1 and M1 phenotypes, respectively. Furthermore, PF11 (30, 100 μM) inhibited the induction of N1 neutrophils by conditioned media from oxygen glucosedeprivation/re-oxygenation (OGD/R)-induced ischemic neurons and promoted the polarization of neutrophils to N2 phenotypes. In addition, PF11 (100 μM) attenuated the exacerbation of N1 neutrophils and facilitated the protection of N2 neutrophils on OGD/R-induced neuronal damage. Similarly, PF11 (100 μM) inhibited the induction of M1 macrophages by conditioned media from ischemic neurons and facilitated the polarization of macrophages to M2 phenotypes. What's more, PF11 (100 μM) attenuated the aggravation of M1 macrophages and promoted the protection of M2 macrophages on OGD/R-induced primary neuron injury. In summary, the present study indicates that PF11 ameliorates ischemic neuron damage by regulating neutrophils and macrophages polarization, suggesting that neutrophils and macrophages may be promising targets for the treatment of cerebral ischemia.

Abstract TMP24: Soluble St2 Links Innate Inflammation to Secondary Injury After Stroke and Subarachnoid Hemorrhage

Background: We recently found that soluble ST2 (sST2) is a plasma marker that predicts neurological outcome after ischemic stroke and aneurysmal subarachnoid hemorrhage. We sought to extend these findings by studying sST2 associations with markers of secondary brain injury and peripheral innate immunity. Methods: We studied 241 acute ischemic stroke (AIS) patients with sST2 level measured on admission (7.4 ± 3.7 hrs after stroke onset) and at least one follow-up brain imaging study, obtained at a mean of 2.2 ± 1.4 days after stroke onset. A subgroup (n=147) had a second sST2 measurement at a mean of 2.1 ± 1.7 days after stroke onset. A separate cohort of 110 subarachnoid hemorrhage (SAH) patients were studied who had plasma sST2 measured at approximately 3.5 ± 1.2 days after ictus. Markers of secondary brain injury included edema after AIS (midline shift), and delayed cerebral ischemia (DCI) or epileptiform discharges on EEG after SAH. The relationships between sST2 level and outcome measures were assessed. Primary blood mononuclear cells from SAH patients and elective aneurysm controls were analyzed by multiparameter flow cytometry to phenotype the peripheral immune response. Results: In the AIS cohort, baseline plasma sST2 level was associated with the presence of midline shift (46.1 vs. 41.8 ng/mL, p=0.017), which further increased at 48 hr after stroke onset (50.6 vs. 38.4 ng/mL, p=0.006). In the SAH cohort, median sST2 in patients who developed new epileptiform abnormalities was higher compared to patients who did not (114.8 ng/ml vs. 74.7 ng/ml, p=0.024). Higher median sST2 concentration was also observed in those patients with DCI (90.8 vs 53.7ng/mL, p=0.003). In patients with high sST2, flow cytometry identified a peripheral monocyte population with decreased expression of CD14 (4.27x105 ± 2950 A.U. vs. 5.64x105 ± 1290 A.U., p&lt;0.001), and increased expression of CD16 (39,960 ± 272 A.U. vs. 34,869 ± 183 A.U., p&lt;0.001). Conclusion: Plasma sST2 independently predicts edema after stroke, and DCI and epileptiform abnormalities after subarachnoid hemorrhage. Elevated sST2 is also associated with changes in peripheral innate immune cells. These data suggest that sST2 links the innate immune response to secondary brain injury.

Activated Bone Marrow-Derived Macrophages Eradicate Alzheimer's-Related Aβ42 Oligomers and Protect Synapses.

Impaired synaptic integrity and function due to accumulation of amyloid β-protein (Aβ42) oligomers is thought to be a major contributor to cognitive decline in Alzheimer's disease (AD). However, the exact role of Aβ42 oligomers in synaptotoxicity and the ability of peripheral innate immune cells to rescue synapses remain poorly understood due to the metastable nature of oligomers. Here, we utilized photo-induced cross-linking to stabilize pure oligomers and study their effects vs. fibrils on synapses and protection by Aβ-phagocytic macrophages. We found that cortical neurons were more susceptible to Aβ42 oligomers than fibrils, triggering additional neuritic arborization retraction, functional alterations (hyperactivity and spike waveform), and loss of VGluT1- and PSD95-excitatory synapses. Co-culturing neurons with bone marrow-derived macrophages protected synapses against Aβ42 fibrils; moreover, immune activation with glatiramer acetate (GA) conferred further protection against oligomers. Mechanisms involved increased Aβ42 removal by macrophages, amplified by GA stimulation: fibrils were largely cleared through intracellular CD36/EEA1+-early endosomal proteolysis, while oligomers were primarily removed via extracellular/MMP-9 enzymatic degradation. In vivo studies in GA-immunized or CD115+-monocyte-grafted APPSWE/PS1ΔE9-transgenic mice followed by pre- and postsynaptic analyses of entorhinal cortex and hippocampal substructures corroborated our in vitro findings of macrophage-mediated synaptic preservation. Together, our data demonstrate that activated macrophages effectively clear Aβ42 oligomers and rescue VGluT1/PSD95 synapses, providing rationale for harnessing macrophages to treat AD.

Increased ileal bile acid binding protein and galectin-9 are associated with mild cognitive impairment and Alzheimer's disease

Enterocyte damage and subsequent microbial translocation drive neuroinflammation in the pathogenesis of Alzheimer's disease (AD). Human ileal bile acid binding protein (I-BABP) and intestinal fatty acid binding proteins (I-FABP) are the indicators of enterocyte damage. Lipopolysaccharide-binding protein (LBP) is an indirect marker of microbial translocation. The activation of peripheral innate immune cells plays a crucial role in modulating AD progression. Galectin-9 is a versatile immunomodulatory molecule. The purpose of this study was to determine I-FABP, I-BABP, LBP, and galectin-9 levels in MCI and AD and investigate the relationship between I-FABP, I-BABP, LBP and galectin-9. In this study, I-FABP, I-BABP, LBP, and galectin-9 levels were measured using ELISA assay in 115 AD patients, 115 MCI patients, and 115 non-demented control subjects. Increased I-BABP and galectin-9 were observed in MCI and AD patients. Furthermore, AD patients had higher I-BABP and galectin-9 levels compared with MCI patients. However, I-FABP and LBP in three groups had no difference. I-BABP levels were positively correlated with galectin-9, after adjusting confounding factors (r = 0.409, p < 0.001). In addition, multivariate analysis revealed that increased I-BABP and galectin-9 levels were significantly associated with reduced mini-mental state examination (MMSE) score. In conclusion, galectin-9 is correlated with I-BABP after adjusting confounding covariates. Moreover, increased I-BABP and galectin-9 in MCI and AD are significant factors for reduced MMSE score. Further studies are needed.

131 CLADIN: CLADribine and INnate immune responses

IntroductionCladribine Tablets (Mavenclad®) is nucleoside analogue of deoxyadenosine, and an oral treatment for relapsing remitting MS (RRMS). In RRMS clinical trials, Cladribine has been shown to reduce brain atrophy, relapse rates, and new lesions on brain MRI. P2X7R is a purinergic receptor expressed in innate immune cells, and is thought to play a critical role in neuroinflammation. The mechanism of action of Cladribine on peripheral innate immune cells (monocytes), and its effect on P2X7R, is unclear, and forms the basis of this study.MethodsThis will be a Phase IV, multi-centre, 3 year, translational trial. Patients who are starting Cladribine as part of their routine clinical care will consent to take part in the study. Monocyte numbers and activation states will be measured at various times prior and after commencement of therapy. In addition, and in an in vitro setting the effect of Cladribine on P2X7R expression and function will be assessed, as well as measuring various cytokines/chemokines in serum. The laboratory data will also be correlated with clinical data from another long-term Cladribine study, CLOBAS.ResultsThis study has been approved by Alfred Health Human Research Ethics Committee. The study is to commence in April 2019.ConclusionThis study will shed light on whether Cladribine is exerting its beneficial effects via action on peripheral monocytes and alterations of their P2X7Rs. The laboratory and clinical data will be analysed to understand the relationship between innate immune parameters and patient outcome.

Attenuated inflammatory response of monocyte-derived macrophage from patients with BD: a preliminary report

BackgroundInnate immune system dysfunction has been recognized as an important element in the pathophysiology of bipolar disorder (BD). We aimed to investigate whether there are differences in the response of macrophages derived from patients in the early stages and late stages of BD and healthy subjects.MethodsHuman monocytes purified from peripheral blood mononuclear cells (PBMCs) of patients with BD type I (n = 18)—further classified into early- and late stage BD patients according to their functioning- and from healthy individuals (n = 10) were differentiated into macrophages in vitro. Monocyte-derived macrophages (M) were exposed to IFNγ plus LPS-M(IFNγ + LPS)- or IL-4-M(IL-4)—to induce their polarization into the classical (also called M1) or alternative (also called M2) activation phenotypes, respectively; or either Mψ were not exposed to any stimuli characterizing the resting state (denominated M0). In vitro secretion of cytokines, such as IL-1β, IL-6, IL-10, and TNF-α, was used as an index of macrophage activity.ResultsM(IFNγ + LPS) from late-stage BD patients produced less amount of IL-1β, IL-6, and IL-10 when compared to early-stage BD patients and healthy controls. Following alternative activation, M(IL-4) derived from late-stage patients secreted less IL-6 compared to the other groups. TNFα was less secreted by all macrophage phenotypes derived from late-stage patients when compared to healthy controls only (p < 0.005). Mψ from late-stage patients exhibited lower production of IL-1β and IL-10 compared to macrophages from healthy subjects and early-stage patients respectively. Interestingly, cytokines secretion from M(IFNγ + LPS), M(IL-4) and Mψ were similar between early-stage patients and healthy controls.ConclusionOur results suggest a progressive dysfunction in the response of peripheral innate immune cells of BD patients in the late stages of the illness. This failure in the regulation of the immune system function may be implicated in the multisystemic progression of BD.

Tumour Necrosis Factor-\u03b1 Inhibition Improves Stroke Outcome in a Mouse Model of Rheumatoid Arthritis

Rheumatoid Arthritis (RA) is a chronic inflammatory disorder where incidence and severity of myocardial infarction are increased. Data on the incidence and outcome of stroke are conflicting. Thus, we investigated outcome after Ischemia/Reperfusion (I/R) brain injury in a mouse model of RA and assessed for the role of the tumour necrosis factor-α (TNF-α) inhibitor Infliximab herein. We used a TNF-α reliant mouse model of RA. RA and wildtype (WT) animals were treated with vehicle (RA/WT) or Infliximab (RA Infliximab) for 4 weeks, before undergoing I/R brain injury. RA-animals displayed larger strokes and poorer neurological performance. Immunohistochemistry on brain sections revealed increased numbers of resident and peripheral innate immune cells (microglia and macrophages); increased Blood-Brain-Barrier (BBB)-disruption; decreased levels of the tight junction proteins (TJPs) claudin-5 and occludin; increased expression of matrix-metalloproteinases (MMP)-3 and -9 and enhanced lipid peroxidation. Treatment with Infliximab corrected these alterations. We show that RA associates to worse stroke-outcome via exacerbated BBB degradation by decrease of the TJPs claudin-5 and occludin. We identified MMPs-3 and -9 and increased oxidative stress as potential mediators thereof. Increased numbers of resident and peripheral innate immune cells (microglia and macrophages) may in turn contribute to all these effects. Infliximab-treatment restored the phenotype of RA-mice to baseline. Our data provide evidence clearly linking RA to adverse stroke-outcome in mice and indicate an approved TNF-α inhibitor as a potential strategy to reduce stroke-burden in this setting.