The Notch1/CD22 signaling axis disrupts Treg function in SARS-CoV-2-associated multisystem inflammatory syndrome in children.

Multisystem inflammatory syndrome in children (MIS-C) evolves in some pediatric patients following acute infection with SARS-CoV-2 by hitherto unknown mechanisms. Whereas acute-COVID-19 severity and outcomes were previously correlated with Notch4 expression on Tregs, here, we show that Tregs in MIS-C were destabilized through a Notch1-dependent mechanism. Genetic analysis revealed that patients with MIS-C had enrichment of rare deleterious variants affecting inflammation and autoimmunity pathways, including dominant-negative mutations in the Notch1 regulators NUMB and NUMBL leading to Notch1 upregulation. Notch1 signaling in Tregs induced CD22, leading to their destabilization in a mTORC1-dependent manner and to the promotion of systemic inflammation. These results identify a Notch1/CD22 signaling axis that disrupts Treg function in MIS-C and point to distinct immune checkpoints controlled by individual Treg Notch receptors that shape the inflammatory outcome in SARS-CoV-2 infection.

Immune modulation as a consequence of SARS-CoV-2 infection.

Erroneous immune responses in COVID-19 could have detrimental effects, which makes investigation of immune network underlying COVID-19 pathogenesis a requisite. This study aimed to investigate COVID-19 related alterations within the frame of innate and adaptive immunity. Thirty-four patients clinically diagnosed with mild, moderate and severe COVID-19 disease were enrolled in this study. Decreased ILC1 and increased ILC2 subsets were detected in mild and moderate patients compared to healthy controls. NK cell subsets and cytotoxic capacity of NK cells were decreased in severe patients. Moreover, CD3+ T cells were reduced in severe patients and a negative correlation was found between CD3+ T cells and D-dimer levels. Likewise, moderate and severe patients showed diminished CD3+CD8+ T cells. Unlike T and NK cells, plasmablast and plasma cells were elevated in patients and IgG and IgA levels were particularly increased in severe patients. Severe patients also showed elevated serum levels of pro-inflammatory cytokines such as TNF-α, IL-6 and IL-8, reduced intracellular IFN-γ and increased intracellular IL-10 levels. Our findings emphasize that SARS-CoV-2 infection significantly alters immune responses and innate and acquired immunity are differentially modulated in line with the clinical severity of the disease. Elevation of IL-10 levels in NK cells and reduction of CD3+ and CD8+ T cells in severe patients might be considered as a protective response against the harmful effect of cytokine storm seen in COVID-19.

Effect of different cytokines in combination with IL-15 on the expression of activating receptors in NK cells of patients with Behçet's disease.

Behçet's disease (BD) is a systemic, autoinflammatory, chronic disorder which affects various parts of the body in genetically susceptible individuals. BD has a multi-factorial etiopathogenesis which encompasses both innate and adaptive arms of immunity. NK cells, which kill virus-infected or malign cells and provide interaction between adaptive and innate immune system, are also known to involve in the pathogenesis of autoimmune/autoinflammatory diseases including BD. NK cells function in immune responses via the signals obtained from surface-expressed activating and inhibitory receptors. In this study, we aimed to explore NK cell activation status by measuring the levels of activation marker CD69 and activating receptors NKG2D, NKp30, and NKp46 as well as proliferative and cytotoxic capacities in response to stimulation with interleukin (IL)-15-combined cytokines in BD patients. CD4+ and CD8+ T cell responses were also evaluated to compare with those of NK cells. As a result, the expression of activating receptors on NK cells was demonstrated to be varied among patients with active and inactive BD and healthy controls. The proliferation levels of NK cells were elevated in BD patients, especially in inactive phase of disease compared to healthy controls. Additionally, CD107a levels of inactive BD patients were detected to be lower in comparison with healthy controls and active BD patients. These findings suggest that BD patients in active and inactive phases display different activation status of NK cells which indicate NK cells might be associated with immune attacks and remissions during the course of BD.

Notch1-CD22-Dependent Immune Dysregulation in the SARS-CoV2-Associated Multisystem Inflammatory Syndrome in Children.

Multisystem inflammatory syndrome in children (MIS-C) evolves in some pediatric patients following acute infection with SARS-CoV-2 by hitherto unknown mechanisms. Whereas acute-COVID-19 severity and outcome were previously correlated with Notch4 expression on regulatory T (Treg) cells, here we show that the Treg cells in MIS-C are destabilized in association with increased Notch1 expression. Genetic analysis revealed that MIS-C patients were enriched in rare deleterious variant impacting inflammation and autoimmunity pathways, including dominant negative mutations in the Notch1 regulators NUMB and NUMBL. Notch1 signaling in Treg cells induced CD22, leading to their destabilization in an mTORC1 dependent manner and to the promotion of systemic inflammation. These results establish a Notch1-CD22 signaling axis that disrupts Treg cell function in MIS-C and point to distinct immune checkpoints controlled by individual Treg cell Notch receptors that shape the inflammatory outcome in SARS-CoV-2 infection.

Haemophagocytic lymphohistiocytosis in a patient with familial Mediterranean fever and miliary tuberculosis: a case report.

Haemophagocytic lymphohistiocytosis (HLH) is a lethal complication of several infections, especially viral origin. Mycobacterium tuberculosis infection can also lead to HLH, yet it is an uncommon trigger. Considering the role of increased cytokines in HLH, autoinflammatory conditions, such as familial Mediterranean fever (FMF), might contribute to its development. Nevertheless, the possible relationship between FMF and HLH has been suggested only in some case reports. We present a case of FMF who admitted to the hospital with consitutional symptoms and chest pain regarding to recurrent pericarditis. On a blood test, pancytopenia and elevated acute phase reactants were seen. Fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography demonstrated positive FDG uptake sites on both the right and left surrenal glands, the visceral layer of pericard, and reactive lymphadenomegalies at multiple mediastinal regions. Bone marrow biopsy revealed haemophagocytosis. Methylprednisolone treatment was initiated. Despite immunosuppressive treatment, clinical and biochemical parameters deteriorated; thus, a thorax computed tomography was executed. Findings were consistent with miliary tuberculosis infection. M. tuberculosis was detected in blood culture and bronchoalveolar lavage culture material. Also, bone marrow and surrenal biopsy material revealed necrotising caseating granuloma.

Notch4 signaling limits regulatory T-cell-mediated tissue repair and promotes severe lung inflammation in viral infections.

A cardinal feature of COVID-19 is lung inflammation and respiratory failure. In a prospective multi-country cohort of COVID-19 patients, we found that increased Notch4 expression on circulating regulatory T (Treg) cells was associated with disease severity, predicted mortality, and declined upon recovery. Deletion of Notch4 in Treg cells or therapy with anti-Notch4 antibodies in conventional and humanized mice normalized the dysregulated innate immunity and rescued disease morbidity and mortality induced by a synthetic analog of viral RNA or by influenza H1N1 virus. Mechanistically, Notch4 suppressed the induction by interleukin-18 of amphiregulin, a cytokine necessary for tissue repair. Protection by Notch4 inhibition was recapitulated by therapy with Amphiregulin and, reciprocally, abrogated by its antagonism. Amphiregulin declined in COVID-19 subjects as a function of disease severity and Notch4 expression. Thus, Notch4 expression on Treg cells dynamically restrains amphiregulin-dependent tissue repair to promote severe lung inflammation, with therapeutic implications for COVID-19 and related infections.

Inflammatory status might direct ILC and NK cells to IL-17 expressing ILC3 and NK subsets in Behcet's disease.

Innate lymphoid cells (ILCs) are lymphoid cells that have important effector and regulatory functions in innate immunity and tissue remodeling. Uncontrolled activation and proliferation of ILCs can contribute to inflammatory autoimmune diseases. Behcet's disease (BD) is a complex systemic inflammatory disorder of unknown etiology. It has been shown that natural killer (NK) cells may play an immunoregulatory role in BD, however the role of ILCs is unknown. In this study, the levels and functions of ILCs and NK cell subsets in BD patients were investigated. Cell surface and cytotoxic granules (perforin and granzyme) expression of NK cells and ILCs were evaluated and labeled according to whole blood lysing protocol in peripheral blood samples obtained from the patients and healthy subjects. Cytokine levels of NK cells were investigated in stimulated peripheral blood mononuclear cells. All data were analyzed by flow cytometry. Total ILC and ILC3+ cells were increased in active BD patients compared to inactive BD patients and healthy subjects. There was no significant difference between the patients and healthy subjects regarding NK cell surface and intracellular molecule expression. Although, an increase in IFN-γ and IL-17, and a decrease in IL-4 levels were observed in CD56dim NK cell subset of BD patients. Recent studies showed increased neutrophilic infiltration and IL-17 secreting Th17 cells in BD patients. It is known that ILC3+cells are similar to Th17 subset regarding their cytokine profile and transcription factor expression patterns. Results of current study may suggest that inflammatory microenvironment in BD patients might direct ILC cells to differentiate into ILC3+ subset, and IL-17 released by NK cells might have a role in neutrophilic infiltration.

Generalized Fixed Drug Eruption Induced by Fluconazole Without Cross-Reactivity to Itraconazole: Lymphocyte Transformation Test Confirms the Diagnosis.

We present a rare case of generalized fixed drug eruption caused by fluconazole. A 45-year-old female patient was referred to our outpatient clinic because of suspicious drug eruptions that occurred 5 months earlier and resolved within a month. The patient had sequela of hyperpigmentation on her arms, legs, back, and abdomen after oral administration of the fourth dose of 150 mg of fluconazole once daily because of vaginal candidiasis. Patch tests with the culprit drug applied both on unaffected skin areas and over one of the lesions were negative. A lymphocyte transformation test was performed and in response to fluconazole, CD4+ T cells significantly proliferated. Because the patient needed a safe antifungal drug for her recurrent vaginal candidiasis symptoms, a single-blind placebo-controlled drug provocation test was performed with itraconazole and was negative. Accordingly, 200 mg of itraconazole once daily was given for 10 days safely.

Peripheral blood NK cells expressing HLA-G, IL-10 and TGF-ß in healthy donors and breast cancer patients.

Human natural killer (NK) cells are not only professional cytotoxic cells integrated into effector branch of innate immunity, but they are also regulatory cells, managing different immune processes. Immunoregulatory NK cells, expressing HLA-G and IL-10, have been generated in vitro from human hematopoietic progenitors and found in vivo among decidual NK cells of pregnant women. Human peripheral blood NK cells have been shown to acquire suppressive properties after HLA-G uptake during trogocytosis. Moreover, it has been shown that circulating NK cells contain a trace amount of cells producing TGF-ß and IL-10, which exert a suppressive influence upon innate and adaptive immunity. In this study, we report on a minor subset of peripheral blood HLA-G(+) NK cells possessing suppressive activity toward effector functions of NK cells. Further we demonstrate an increased number of circulating HLA-G(+), IL-10(+), and TGF-ß(+) NK cells in breast cancer patients which might impair efficiency of anti-tumor immunity.

Plasma concentrations of soluble cytokine receptors in euthymic bipolar patients with and without subsyndromal symptoms.

BACKGROUND: Current evidence suggests that high concentrations of pro-inflammatory markers are associated with bipolar disorder characterized by severe impairment during inter-episodic periods, reduced treatment response and persistent subsyndromal symptoms. We tested whether persistent subsyndromal symptoms in euthymic bipolar patients were associated with markers of an ongoing chronic pro-inflammatory process. METHODS: Forty-five euthymic bipolar patients (22 with subsyndromal symptoms (BD+) and 23 without subsyndromal symptoms (BD-) and 23 well controls (WC) were recruited for assessment of soluble tumor necrosis factor receptor-1 (sTNF-R1), soluble interleukin-6 receptor (sIL-6R) and soluble interleukin-2 receptor (sIL-2R) concentrations. Soluble cytokine receptor concentrations were assessed using enzyme-linked immunosorbent assay. RESULTS: In comparison to WC, sTNF-R1 concentration was higher in both BD- and BD+ (age and sex adjusted standardized ß, respectively: ß = 0.34, p = 0.012 and ß = 0.41, p = 0.003). Similarly, compared to WC, sIL-6R concentration was higher in both BD- and BD+ (age and sex adjusted standardized ß, respectively: ß = 0.44, p = 0.001 and ß = 0.37, p = 0.008). There was no difference between BD- and BD+ in the concentration of either sTNF-R1 or sIL-6R; plasma concentration of sIL-2R was not analyzed as 75% percent of the samples were non-detectable. CONCLUSIONS: Although bipolar patients present with a pro-inflammatory shift compared to well controls, subsyndromal symptoms are not associated with additive increasing effects. Longitudinal studies with larger samples are required to clarify the relationship between illness course and inflammatory markers in bipolar disorder.

Cytokine levels in euthymic bipolar patients.

BACKGROUND: The pathophysiology of bipolar disorder is not thoroughly understood. Several studies have investigated the possible role of cytokines in psychiatric disorders, based on their role in neuro-immune modulation; however, findings in studies on bipolar disorder remain limited and contradictory, and most studies have focused on either manic or depressive episodes. These studies suggest that both manic and depressive episodes could be pro-inflammatory states. The present study aimed to determine whether there are enduring differences in cytokine levels-unrelated to the effects of medication-between euthymic bipolar patients and healthy controls. METHODS: The study included 31 euthymic bipolar patients-16 medication-free (MF) and 15 on lithium monotherapy (LM) and 16 healthy volunteers in whom serum cytokine levels were measured. The 3 groups were homogenous in terms of age, gender, and ethnicity. IFN-γ, TNF-α, IL-2, IL-4, IL-5, and IL-10 levels were measured in all groups using flow cytometry. RESULTS: There were no differences in cytokine levels between MF euthymic bipolar patients and healthy controls. TNF-α and IL-4 levels in LM euthymic bipolar patients were higher than in both the MF euthymic bipolar patients and controls. LIMITATIONS: The small and strictly selected study sample could limit the generalizability of the findings. CONCLUSIONS: Cytokine production in MF euthymic bipolar patients was similar to that in healthy controls. The present study shows that the pro-inflammatory state resolves in euthymia and that lithium had an influence on the cytokine profile, which could create a confounding factor while investigating disease- related immunopathology of bipolar disorder.