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.

[Analysis of IFN-γR1 (CD119) and IL-12Rß1 (CD212) Deficiency by Flow Cytometry]. / IFN-γR1 (CD119) ve IL-12Rß1 (CD212) Eksikliginin Akan Hücre Ölçer ile Analizi.

Mendelian susceptibility to mycobacterial diseases (MSMD) is a rare primary immune deficiency (PID). IL-12Rß1 deficiency is the most frequently observed of more than 16 genetic defects that have been identified for MSMD. Genetic and immunological tests are remarkable in the diagnosis of PID. In this study, it was aimed to determine the expression of IFN-γR1 and IL-12Rß1 in patients with MSMD, their relatives, and healthy individuals and to evaluate the importance of flow cytometry as a fast and reliable method in the diagnosis of MSMD. IFN-γR1 and IL-12Rß1 expression levels were analyzed in 32 volunteers including six patients, six relatives, and 20 healthy individuals. The normal range of IFN-γR1 and IL-12Rß1 levels among healthy individuals were determined. IL-12Rß1 expression level in lymphocytes was found to be low in one patient's relative, and less than 1% in three patients and in one patient's relative. It was observed that the IL-12Rß1 expression levels of the patient with STAT1 deficiency were increased compared to the healthy individuals. No difference was found in the expression levels of IFN-γR1 and IL-12Rß1 in one patient, but IFN-γR1 expression was decreased in one patient compared to healthy individuals. Our results show that the determination of IL-12Rß1 and IFN-γR1 deficiencies by flow cytometry can be used as a rapid and reliable method for the diagnosis of MSMD. The use of this method as a screening test will enable early diagnosis especially in patients whose genetic diagnosis has not been confirmed and clinically compatible with MSMD. In addition, it is thought that IL-12Rß1 and IFN-γR1 range data obtained from healthy individuals will be considered as a reference source in routine and research studies to be conducted with MSMD.

Decline of humoral immune responses after natural SARS-CoV-2 infection can be efficiently reversed by vaccination.

Our aim was to analyze severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibody level kinetics after coronavirus disease 2019 (COVID-19) infection and determine the efficiency of vaccination on SARS-CoV-2-specific antibody levels. The study included 50 SARS-CoV-2 infected and 70 uninfected cases. Levels of SARS-CoV-2-specific IgG nucleocapsid protein (IgG-NP), IgG spike protein (IgG-SP), IgM nucleocapsid protein (IgM-NP), and IgA spike protein (IgA-SP) antibodies were evaluated by an enzyme-linked immunosorbent assay in sera obtained at baseline, 1st, 3rd, and 6th month follow-up visits for infected cases and at postvaccination visits for all cases. In symptomatic cases (n = 50), IgG-SP levels were decreased in 6 months compared with baseline, while IgA-SP levels were significantly increased. IgG-NP levels were significantly decreased in symptomatic cases at the 6-month visit. After vaccination, IgG-SP levels were increased in symptomatic cases compared with prevaccination levels. Among subjects vaccinated with CoronaVac (the Sinovac COVID-19 vaccine), infected cases had approximately double the IgG-SP level of uninfected cases. SARS-CoV-2-specific antibody levels were higher at the baseline in symptomatic cases. Nevertheless, all infected cases showed significantly reduced IgG-SP levels at the 6th month. Vaccination effectively increased IgG-SP levels.

Investigation of AID, Dicer, and Drosha Expressions in Patients with Chronic Lymphocytic Leukemia.

Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries. Cytogenetic lesions such as del13q14, del11q22.3, and del17p13 are identified in 50-60% of patients. Activation-induced cytidine deaminase (AID) plays a central role in somatic hyper mutation (SHM) and class switch recombination (CSR) and functions on Ig genes, but also target non-Ig genes, and over-expression of AID can lead to point mutations or translocations in non-Ig genes such as IgH/Myc translocation. Dicer and Drosha, which have a role in activation process of miRNA, also act in a double-strand DNA break (DSB) repair mechanism. In this study, whether the changes of AID, Dicer and Drosha expressions may be associated with both deletions and clinical outcomes in patients with CLL were investigated. AID expressions were increased in patients with CLL. However, cell lysate AID protein levels were only increased in patients with del17p or del11q who have poor prognosis. Decreased Dicer expressions were found in patients with deletion, whereas increased Drosha expressions were found in patients without deletion and with del13q. According to Rai and Binet staging systems, advanced-stage patients showed increased AID protein levels, decreased Dicer and Drosha expressions. Our findings may suggest that high AID expression and lower Dicer expression were observed in patients with CLL especially del17p and del11q and might associated with deletions such as del17p and del11q. AID, Dicer, and Drosha expressions might be used as an indicator of prognosis for CLL.

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.

Functions of NK and iNKT cells in pediatric and adult CVID, ataxia telangiectasia and agammaglobulinemia patients.

Primary immune deficiencies (PID) are known to be more than 400 genetic defects caused by the impairment in development and/or functions of the immune system. Common Variable Immunodeficiency (CVID), Ataxia Telangiectasia (AT) and Agammaglobulinemia (AG) are examples of the most common immunodeficiency syndrome. Natural killer (NK) cells are a component of innate immune system and play a major role in the host-rejection of both tumors and virally infected cells. iNKT cells have a role in autoimmune and infectious diseases and controlling of tumor rejection. In this study, NK and iNKT cells and their functions, and intracellular cytokine amount are aimed to determine in patients that suffer CVID, AT and AG. NKp30, NKp46, NKG2D, perforin and granzyme mRNA expression levels were analyzed using RT-PCR. Receptors, cytokine amount of NK cell subset and iNKT were analyzed by flow cytometry. Decreased CD3+ T and elevated NK cell subset in pediatric AT were found. Expression of NKp44 was decreased in adult AG, but not in pediatric patients. Low NKp44 expression in CD3-CD16+CD56dim NK cell subset was found in pediatric AT patients. High HLA-DR, perforin and granzyme expression were found in CD3-CD16+CD56dim NK cell subset of pediatric CVID and AT patients. Alteration of the number of NK subsets, NK receptor expression and cytokine production were observed in pediatric patients compared to healthy subjects.

The Role of Natural Killer Cells in Autoimmune Diseases.

Natural killer (NK) cells, the large granular lymphocytes differentiated from the common lymphoid progenitors, were discovered in early 1970's. They are members of innate immunity and were initially defined by their strong cytotoxicity against virus-infected cells and by their important effector functions in anti-tumoral immune responses. Nowadays, NK cells are classified among the recently discovered innate lymphoid cell subsets and have capacity to influence both innate and adaptive immune responses. Therefore, they can be considered as innate immune cells that stands between the innate and adaptive arms of immunity. NK cells don't express T or B cell receptors and are recognized by absence of CD3. There are two major subgroups of NK cells according to their differential expression of CD16 and CD56. While CD16+CD56dim subset is best-known by their cytotoxic functions, CD16-CD56bright NK cell subset produces a bunch of cytokines comparable to CD4+ T helper cell subsets. Another subset of NK cells with production of interleukin (IL)-10 was named as NK regulatory cells, which has suppressive properties and could take part in immune-regulatory responses. Activation of NK cells is determined by a delicate balance of cell-surface receptors that have either activating or inhibitory properties. On the other hand, a variety of cytokines including IL-2, IL-12, IL-15, and IL-18 influence NK cell activity. NK-derived cytokines and their cytotoxic functions through induction of apoptosis take part in regulation of the immune responses and could contribute to the pathogenesis of many immune mediated diseases including ankylosing spondylitis, Behçet's disease, multiple sclerosis, rheumatoid arthritis, psoriasis, systemic lupus erythematosus and type-1 diabetes. Dysregulation of NK cells in autoimmune disorders may occur through multiple mechanisms. Thanks to the rapid developments in biotechnology, progressive research in immunology enables better characterization of cells and their delicate roles in the complex network of immunity. As NK cells stand in between innate and adaptive arms of immunity and "bridge" them, their contribution in inflammation and immune regulation deserves intense investigations. Better understanding of NK-cell biology and their contribution in both exacerbation and regulation of inflammatory disorders is a requisite for possible utilization of these multi-faceted cells in novel therapeutic interventions.

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.