Leucine-Rich Glioma-Inactivated 1 (LGI1) Protein Stimulates Proliferation and IL-10 Production in Peripheral Blood Mononuclear Cells of Patients with LGI1 Antibody-Mediated Autoimmune Encephalitis In Vitro.

Limbic encephalitis (LE) due to anti-leucine-rich glioma-inactivated 1 (LGI1) antibodies is an autoimmune disease characterized by distinct clinical features unique to LGI1 LE, such as faciobrachial dystonic seizures. However, it is unclear whether an additional disease-related LGI1 antigen-specific T cell response is involved in the pathogenesis of this disease. To address this question, we studied the effect of recombinant LGI1 on the proliferation and effector-specific cytokine production (IFN-γ, IL-5, IL-10, and IL-17) of peripheral blood mononuclear cells (PBMCs) from patients with LGI1 LE and healthy controls. We observed that recombinant LGI1 stimulated the proliferation of PBMCs from patients with LGI1 LE, but not from healthy controls. Cytokine measurement of cell culture supernatants from PBMCs incubated with recombinant LGI1 revealed a highly significant increase in IL-10 release in PBMCs from patients with LGI1 LE in comparison with healthy controls. These results suggest that LGI1-mediated stimulation of PBMCs from patients with LGI1 LE leads to the establishment of an IL-10-dominated immunosuppressive cytokine milieu, which may inhibit Th1 differentiation and support B cell proliferation, IgG production, and IgG subclass switching.

[General knowledge of frequently applied test procedures in rheumatological and immunological diagnostics and research]. / Allgemeine Kenntnisse zu häufig angewandten Testverfahren in der rheumatologisch-immunologischen Diagnostik und Forschung.

Knowledge of test procedures is essential for an optimal approach in rheumatological and immunological diagnostics as well as for a correct interpretation of the findings. In practice, they are a basis for the independent provision of diagnostic laboratory services. For scientific questions they have become indispensable tools in many areas. This article gives an overview on the most frequently used and important test methods in a comprehensive form. The advantages and performance of the different methods are addressed and the limitations and possible sources or error are discussed. Quality control increasingly plays a decisive role in the diagnostic and scientific practice, with the legal regulations applying to all test procedures in laboratory diagnostics. For the discipline of rheumatology, the rheumatological and immunological diagnostics are of particular importance as the majority of the known disease-specific markers are detectable by means of these procedures. At the same time, immunological laboratory diagnostics are a highly interesting field of activity which are expected to have a strong impact on the future developments in rheumatology.

Zinc aspartate induces proliferation of resting and antigen-stimulated human PBMC under high-density cell culture condition.

BACKGROUND: Zinc, one of the most important essential trace elements in the human body, regulates a wide range of cellular functions of immune cells, such as proliferation, differentiation and survival. Zinc deficiency affects both the innate and adaptive immune system. Zinc supplementation was discussed as possible therapy for infectious diseases and T cell-mediated autoimmune diseases. However, the influence of commercial zinc preparations on proliferation and cytokine production of resting and antigen-stimulated peripheral blood mononuclear cells (PBMC) has not yet been completely investigated. METHODS: Here, we examined whether zinc aspartate (Unizink®), an approved drug to treat zinc deficiency in patients, induces proliferation, cytokine production, and induction of apoptosis/caspase 3/7 activity of resting PBMC under high-density cell culture condition. In addition, we performed antigen-specific proliferation experiments, where PBMCs of healthy donors vaccinated against Influenza A (H1N1) and/or SARS-CoV-2 were stimulated with Influenza A (H1N1) peptides or SARS-CoV-2 peptides as well as the Mixed Lymphocyte Culture (MLC) in the presence of increasing concentrations of zinc aspartate. RESULTS: We observed a dose-dependent enhancement of proliferation and induction of cytokine production (IFN-γ, IL-5, GM-CSF and CXCL10) of resting PBMC in presence of zinc aspartate. The number of cells with active caspase 3/7 and, consecutively, the amount of cells undergoing apoptosis steadily decreased in presence of zinc aspartate. Moreover, zinc aspartate was capable of stimulating antigen-specific PBMC proliferation using MLC or influenza A (H1N1) and SARS-CoV-2 peptides in both a dose-dependent and a donor-specific manner. In the absence of zinc aspartate, we clearly could discriminate two groups of responders: low and high responders to antigenic stimulation. The addition of increasing concentration of zinc aspartate significantly stimulated the proliferation of PBMC from low responders, but not from high responders. CONCLUSION: Taken together, our results suggest that zinc aspartate induces the proliferation of resting and antigen-stimulated PBMCs under high-density cell culture conditions. Thus, zinc might represent a supportive treatment in patients suffering from infectious diseases.

IL-13 determines specific IgE responses and SARS-CoV-2 immunity after mild COVID-19 and novel mRNA vaccination.

After recovery, mild and severe COVID-19 diseases are associated with long-term effects on the host immune system, such as prolonged T-cell activation or accumulation of autoantibodies. In this study, we show that mild SARS-CoV-2 infections, but not SARS-CoV-2 spike mRNA vaccinations, cause durable atopic risk factors such as a systemic Th2- and Th17-type environment as well as activation of B cells responsive of IgE against aeroallergens from house dust mite and mold. At an average of 100 days post mild SARS-CoV-2 infections, anti-mold responses were associated with low IL-13 levels and increased pro-inflammatory IL-6 titers. Acutely severely ill COVID-19 patients instead showed no evidence of atopic reactions. Considering convalescents of mild COVID-19 courses and mRNA-vaccinated individuals together, IL-13 was the predominant significantly upregulated factor, likely shaping SARS-CoV-2 immunity. Application of multiple regression analysis revealed that the IL-13 levels of both groups were determined by the Th17-type cytokines IL-17A and IL-22. Taken together, these results implicate a critical role for IL-13 in the aftermath of SARS-CoV-2 mild infections and mRNA vaccinations, conferring protection against airway directed, atopic side reactions that occur in mildly experienced COVID-19.

Novel insights into mouse models of ectopic proplatelet release.

Mature bone marrow (BM) megakaryocytes (MKs) produce platelets by extending proplatelets into sinusoidal blood vessels. Defects in this process can lead to thrombocytopenia and increased risk of bleeding. Mice lacking the actin-regulatory proteins Profilin 1 (PFN1), Wiskott-Aldrich Syndrome protein (WASp), Actin Related Protein 2/3 complex (Arp2/3), or adhesion and degranulation-promoting adapter protein (ADAP) display thrombocytopenia and ectopic release of (pro)platelet-like particles into the BM compartment, pointing to an important axis of actin-mediated directional proplatelet formation. The mechanism underlying ectopic release in these mice is still not completely understood. However, we hypothesized that similar functional defects account for this observation. We analyzed WASp-, ADAP-, PFN1-, and ARPC2-knockout mice to determine the role of actin reorganization and integrin activation in directional proplatelet formation. ADAP-, ARPC2-, and PFN1-deficient MKs displayed reduced adhesion to collagen, defective F-actin organization, and diminished ß1-integrin activation. WASp-deficient MKs showed the strongest reduction in the adhesion assay of collagen and altered F-actin organization with reduced podosome formation. Our results indicate that ADAP, PFN1, WASp, and ARP2/3 are part of the same pathway that regulates polarization processes in MKs and directional proplatelet formation into BM sinusoids.

Homologous and Heterologous Anti-COVID-19 Vaccination Does Not Induce New-Onset Formation of Autoantibodies Typically Accompanying Lupus Erythematodes, Rheumatoid Arthritis, Celiac Disease and Antiphospholipid Syndrome.

The COVID-19 pandemics has caused the death of almost six million people worldwide. In order to establish collective immunity, the first vaccines that were approved in Germany were the vector virus-based vaccine Vaxzevria and the mRNA vaccines Comirnaty and Spikevax, respectively. As it was reported that SARS-CoV-2 can trigger autoimmunity, it is of significant interest to investigate whether COVID-19 vaccines evoke the formation of autoantibodies and subsequent autoimmunity. Here, we analyzed immune responses after different vaccination regimens (mRNA/mRNA, Vector/Vector or Vector/mRNA) with respect to anti-SARS-CoV-2-specific immunity and the development of autoantibodies well known for their appearance in distinct autoimmune diseases. We found that anti-SARS-CoV-2 antibody levels were 90% lower after Vector/Vector vaccination compared to the other vaccinations and that Vector/mRNA vaccination was more effective than mRNA/mRNA vaccination in terms of IgM and IgA responses. However, until 4 months after booster vaccination we only detected increases in autoantibodies in participants with already pre-existing autoantibodies whereas vaccinees showing no autoantibody formation before vaccination did not respond with sustained autoantibody production. Taken together, our study suggests that all used COVID-19 vaccines do not significantly foster the appearance of autoantibodies commonly associated with lupus erythematodes, rheumatoid arthritis, Celiac disease and antiphospholipid-syndrome but provide immunity to SARS-CoV-2.

Ionic mitigation of CD4+ T cell metabolic fitness, Th1 central nervous system autoimmunity and Th2 asthmatic airway inflammation by therapeutic zinc.

T helper (Th) cells provide immunity to pathogens but also contribute to detrimental immune responses during allergy and autoimmunity. Th2 cells mediate asthmatic airway inflammation and Th1 cells are involved in the pathogenesis of multiple sclerosis. T cell activation involves complex transcriptional networks and metabolic reprogramming, which enable proliferation and differentiation into Th1 and Th2 cells. The essential trace element zinc has reported immunomodulatory capacity and high zinc concentrations interfere with T cell function. However, how high doses of zinc affect T cell gene networks and metabolism remained so far elusive. Herein, we demonstrate by means of transcriptomic analysis that zinc aspartate (UNIZINK), a registered pharmaceutical infusion solution with high bioavailability, negatively regulates gene networks controlling DNA replication and the energy metabolism of murine CD3/CD28-activated CD4+ T cells. Specifically, in the presence of zinc, CD4+ T cells show impaired expression of cell cycle, glycolytic and tricarboxylic acid cycle genes, which functionally cumulates in reduced glycolysis, oxidative phosphorylation, metabolic fitness and viability. Moreover, high zinc concentrations impaired nuclear expression of the metabolic transcription factor MYC, prevented Th1 and Th2 differentiation in vitro and reduced Th1 autoimmune central nervous system (CNS) inflammation and Th2 asthmatic airway inflammation induced by house dust mites in vivo. Together, we find that higher zinc doses impair the metabolic fitness of CD4+ T cells and prevent Th1 CNS autoimmunity and Th2 allergy.

Robust induction of neutralizing antibodies against the SARS-CoV-2 Delta variant after homologous Spikevax or heterologous Vaxzevria-Spikevax vaccination.

Sera of vaccines were assessed by surrogate virus neutralization tests for their capacity to neutralize the SARS-CoV-2 Delta variant. Homologous prime-boost immunization with Moderna's Spikevax as well as heterologous immunization with AstraZeneca's Vaxzevria followed by Moderna's Spikevax were identified as highly potent vaccination regimens for the induction of Delta-neutralizing antibodies.

Enhanced Susceptibility of ADAP-Deficient Mice to Listeria monocytogenes Infection Is Associated With an Altered Phagocyte Phenotype and Function.

The adhesion and degranulation-promoting adaptor protein (ADAP) serves as a multifunctional scaffold and is involved in the formation of immune signaling complexes. To date, only limited data exist regarding the role of ADAP in pathogen-specific immunity during in vivo infection, and its contribution in phagocyte-mediated antibacterial immunity remains elusive. Here, we show that mice lacking ADAP (ADAPko) are highly susceptible to the infection with the intracellular pathogen Listeria monocytogenes (Lm) by showing enhanced immunopathology in infected tissues together with increased morbidity, mortality, and excessive infiltration of neutrophils and monocytes. Despite high phagocyte numbers in the spleen and liver, ADAPko mice only inefficiently controlled pathogen growth, hinting at a functional impairment of infection-primed phagocytes in the ADAP-deficient host. Flow cytometric analysis of hallmark pro-inflammatory mediators and unbiased whole genome transcriptional profiling of neutrophils and inflammatory monocytes uncovered broad molecular alterations in the inflammatory program in both phagocyte subsets following their activation in the ADAP-deficient host. Strikingly, ex vivo phagocytosis assay revealed impaired phagocytic capacity of neutrophils derived from Lm-infected ADAPko mice. Together, our data suggest that an alternative priming of phagocytes in ADAP-deficient mice during Lm infection induces marked alterations in the inflammatory profile of neutrophils and inflammatory monocytes that contribute to enhanced immunopathology while limiting their capacity to eliminate the pathogen and to prevent the fatal outcome of the infection.

Pitavastatin Is a Highly Potent Inhibitor of T-Cell Proliferation.

Repositioning of approved drugs is an alternative time- and cost-saving strategy to classical drug development. Statins are 3-hydroxy-3-methylglutaryl-CoA (HMG CoA) reductase inhibitors that are usually used as cholesterol-lowering medication, and they also exhibit anti-inflammatory effects. In the present study, we observed that the addition of Pitavastatin at nanomolar concentrations inhibits the proliferation of CD3/CD28 antibody-stimulated human T cells of healthy donors in a dose-dependent fashion. The 50% inhibition of proliferation (IC50) were 3.6 and 48.5 nM for freshly stimulated and pre-activated T cells, respectively. In addition, Pitavastatin suppressed the IL-10 and IL-17 production of stimulated T cells. Mechanistically, we found that treatment of T cells with doses <1 µM of Pitavastatin induced hyperphosphorylation of ERK1/2, and activation of caspase-9, -3 and -7, thus leading to apoptosis. Mevalonic acid, cholesterol and the MEK1/2 inhibitor U0126 reversed this Pitavastatin-mediated ERK1/2 activation and apoptosis of T cells. In summary, our results suggest that Pitavastatin is a highly potent inhibitor of T-cell proliferation, which induces apoptosis via pro-apoptotic ERK1/2 activation, thus representing a potential repositioning candidate for the treatment of T-cell-mediated autoimmune diseases.

The Multiple Roles of the Cytosolic Adapter Proteins ADAP, SKAP1 and SKAP2 for TCR/CD3 -Mediated Signaling Events.

T cells are the key players of the adaptive immune response. They coordinate the activation of other immune cells and kill malignant and virus-infected cells. For full activation T cells require at least two signals. Signal 1 is induced after recognition of MHC/peptide complexes presented on antigen presenting cells (APCs) by the clonotypic TCR (T-cell receptor)/CD3 complex whereas Signal 2 is mediated via the co-stimulatory receptor CD28, which binds to CD80/CD86 molecules that are present on APCs. These signaling events control the activation, proliferation and differentiation of T cells. In addition, triggering of the TCR/CD3 complex induces the activation of the integrin LFA-1 (leukocyte function associated antigen 1) leading to increased ligand binding (affinity regulation) and LFA-1 clustering (avidity regulation). This process is termed "inside-out signaling". Subsequently, ligand bound LFA-1 transmits a signal into the T cells ("outside-in signaling") which enhances T-cell interaction with APCs (adhesion), T-cell activation and T-cell proliferation. After triggering of signal transducing receptors, adapter proteins organize the proper processing of membrane proximal and intracellular signals as well as the activation of downstream effector molecules. Adapter proteins are molecules that lack enzymatic or transcriptional activity and are composed of protein-protein and protein-lipid interacting domains/motifs. They organize and assemble macromolecular complexes (signalosomes) in space and time. Here, we review recent findings regarding three cytosolic adapter proteins, ADAP (Adhesion and Degranulation-promoting Adapter Protein), SKAP1 and SKAP2 (Src Kinase Associated Protein 1 and 2) with respect to their role in TCR/CD3-mediated activation, proliferation and integrin regulation.

Zinc Aspartate Induces IL-16 Secretion and Apoptosis in Human T Cells.

T cell activation mediates immunity to pathogens. On the flipside, T cells are also involved in pathological immune responses during chronic autoimmune diseases. We recently reported that zinc aspartate, a registered drug with high bioavailability, dose-dependently inhibits T cell activation and Th1/Th2/Th17 cytokine production of stimulated human and mouse T cells. To understand the suppressive effect of zinc on T cell function, we here investigated the influence of zinc aspartate on human T cells focusing on the secretion of immunosuppressive cytokines, induction of apoptosis, and caspase 3/7 activity. To this end, we monitored either freshly stimulated or pre-activated human T cells in the presence of zinc aspartate from 40-140 µM over a period of 72 h. Under both experimental conditions, we observed a dose-dependent suppression of human T cell proliferation. While IL-1ra, latent TGF-ß1, and IL-10 were dose-dependently reduced, we, unexpectedly, detected elevated levels of IL-16 upon zinc supplementation. In addition, the number of cells with active caspase 3/7 and, consecutively, the amount of cells undergoing apoptosis, steadily increased at zinc aspartate concentrations exceeding 100 µM. Taken together, our findings suggest that zinc aspartate impairs T cell fitness and might be beneficial for the treatment of T cell-mediated autoimmune diseases.

Screening of FDA-Approved Drug Library Identifies Adefovir Dipivoxil as Highly Potent Inhibitor of T Cell Proliferation.

Repositioning of approved drugs for identifying new therapeutic purposes is an alternative, time and cost saving strategy to classical drug development. Here, we screened a library of 786 FDA-approved drugs to find compounds, which can potentially be repurposed for treatment of T cell-mediated autoimmune diseases. Investigating the effect of these diverse substances on mitogen-stimulated proliferation of both, freshly stimulated and pre-activated (48 h) peripheral blood mononuclear cells (PBMCs), we discovered Adefovir Dipivoxil (ADV) as very potent compound, which inhibits T cell proliferation in a nanomolar range. We further analyzed the influence of ADV on proliferation, activation, cytokine production, viability and apoptosis of freshly stimulated as well as pre-activated human T cells stimulated with anti-CD3/CD28 antibodies. We observed that ADV was capable of suppressing the proliferation in both T cell stimulation systems in a dose-dependent manner (50% inhibition [IC50]: 63.12 and 364.8 nM for freshly stimulated T cells and pre-activated T cells, respectively). Moreover, the drug impaired T cell activation and inhibited Th1 (IFN-γ), Th2 (IL-5), and Th17 (IL-17) cytokine production dose-dependently. Furthermore, ADV treatment induced DNA double-strand breaks (γH2AX foci expression), which led to an increase of p53-phospho-Ser15 expression. In response to DNA damage p21 and PUMA are transactivated by p53. Subsequently, this caused cell cycle arrest at G0/G1 phase and activation of the intrinsic apoptosis pathway. Our results indicate that ADV could be a new potential candidate for treatment of T cell-mediated autoimmune diseases. Prospective studies should be performed to verify this possible therapeutic application of ADV for such disorders.

Immune Cell-Type Specific Ablation of Adapter Protein ADAP Differentially Modulates EAE.

The cytosolic adhesion and degranulation-promoting adapter protein ADAP is expressed in various hematopoietic cells including T cells, NK cells, myeloid cells, and platelets but absent in mature B cells. The role of ADAP in T cell activation, proliferation and integrin activation is well-accepted. We previously demonstrated that conventional ADAP knockout mice show a significantly attenuated course of experimental autoimmune encephalomyelitis (EAE). To dissect the impact of different ADAP expressing cell populations on the reduced EAE severity, here, we generated lineage-specific conditional knockout mice. ADAP was deleted in T cells, myeloid cells, NK cells and platelets, respectively. Specific loss of ADAP was confirmed on the protein level. Detailed immunophenotyping was performed to assess the consequence of deletion of ADAP with regard to the maturation and distribution of immune cells in primary and secondary lymphoid organs. The analysis showed equivalent results as for conventional ADAP knockout mice: impaired thymocyte development in ADAPfl/fl Lck-Cre mice, normal NK cell and myeloid cell distribution in ADAPfl/fl NKp46-Cre mice and ADAPfl/fl LysM-Cre mice, respectively as well as thrombocytopenia in ADAPfl/fl PF4-Cre mice. Active EAE was induced in these animals by immunization with the myelin oligodendrocyte glycoprotein35-55 peptide. The clinical course of EAE was significantly milder in mice with loss of ADAP in T cells, myeloid cells and NK cells compared to ADAP-sufficient control littermates. Surprisingly, specific deletion of ADAP in platelets resulted in a more exacerbated disease. These data show that T cell-independent as well as T cell-dependent mechanisms are responsible for the complex phenotype observed in conventional ADAP knockout mice.

IL-10 producing B cells rescue mouse fetuses from inflammation-driven fetal death and are able to modulate T cell immune responses.

Understanding the mechanisms leading to fetal death following maternal subclinical infections is crucial to develop new therapeutic strategies. Here we addressed the relevance of IL-10 secreting B cells (B10) in the maintenance of the immune balance during gestation. µMT females lacking mature B cells presented normal pregnancies, although their fetuses were smaller and their Treg pool did not expand as in B cell sufficient controls. Pregnant µMT females were more susceptible to LPS despite having less Treg; their fetuses died at doses compatible with pregnancy in WT animals. Adoptive transfer of IL-10 negative B effector cells or B cells from IL-10 deficient mice did not modify this outcome. The transfer of B10 cells or application of recombinant murine IL-10 reduced the fetal loss, associated with a normalization of Treg numbers and cytokine modulation at the feto-maternal interface. B cell-derived IL-10 suppressed the production of IL-17A and IL-6 by T cells and promoted the conversion of naïve cells into Treg. B10 cells are required to restore the immune balance at the feto-maternal interface when perturbed by inflammatory signals. Our data position B cells in a central role in the maintenance of the balance between immunity and tolerance during pregnancy.

Characterization of Mice with a Platelet-Specific Deletion of the Adapter Molecule ADAP.

The adhesion and degranulation-promoting adapter protein (ADAP) is expressed in T cells, NK cells, myeloid cells, and platelets. The involvement of ADAP in the regulation of receptor-mediated inside-out signaling leading to integrin activation is well characterized, especially in T cells and in platelets. Due to the fact that animal studies using conventional knockout mice are limited by the overlapping effects of the different ADAP-expressing cells, we generated conditional ADAP knockout mice (ADAPfl/fl PF4-Cretg) (PF4, platelet factor 4). We observed that loss of ADAP restricted to the megakaryocytic lineage has no impact on other hematopoietic cells even under stimulation conditions. ADAPfl/fl PF4-Cretg mice showed thrombocytopenia in combination with reduced plasma levels of PF4 and transforming growth factor ß1 (TGF-ß1). In vitro, platelets from these mice revealed reduced P-selectin expression, lower levels of TGF-ß1 release, diminished integrin αIIbß3 activation, and decreased fibrinogen binding after stimulation with podoplanin, the ligand of C-type lectin-like receptor 2 (CLEC-2). Furthermore, loss of ADAP was associated with impaired CLEC-2-mediated activation of phospholipase Cγ2 (PLCγ2) and extracellular signal-regulated kinase 1/2 (ERK1/2). Induction of experimental autoimmune encephalomyelitis (EAE) in mice lacking ADAP expression in platelets caused a more severe disease. In vivo administration of TGF-ß1 early after T cell transfer reduced EAE severity in mice with loss of ADAP restricted to platelets. Our results reveal a regulatory function of ADAP in platelets in vitro and during autoimmune disease EAE in vivo.

ADAP Promotes Degranulation and Migration of NK Cells Primed During in vivo Listeria monocytogenes Infection in Mice.

The adhesion and degranulation-promoting adaptor protein (ADAP) serves as a multifunctional scaffold and is involved in the formation of immune signaling complexes. To date only limited and moreover conflicting data exist regarding the role of ADAP in NK cells. To extend existing knowledge we investigated ADAP-dependency of NK cells in the context of in vivo infection with the intracellular pathogen Listeria monocytogenes (Lm). Ex vivo analysis of infection-primed NK cells revealed impaired cytotoxic capacity in NK cells lacking ADAP as indicated by reduced CD107a surface expression and inefficient perforin production. However, ADAP-deficiency had no global effect on NK cell morphology or intracellular distribution of CD107a-containing vesicles. Proteomic definition of ADAPko and wild type NK cells did not uncover obvious differences in protein composition during the steady state and moreover, similar early response patterns were induced in NK cells upon infection independent of the genotype. In line with protein network analyses that suggested an altered migration phenotype in naïve ADAPko NK cells, in vitro migration assays uncovered significantly reduced migration of both naïve as well as infection-primed ADAPko NK cells compared to wild type NK cells. Notably, this migration defect was associated with a significantly reduced expression of the integrin CD11a on the surface of splenic ADAP-deficient NK cells 1 day post-Lm infection. We propose that ADAP-dependent alterations in integrin expression might account at least in part for the fact that during in vivo infection significantly lower numbers of ADAPko NK cells accumulate in the spleen i.e., the site of infection. In conclusion, we show here that during systemic Lm infection in mice ADAP is essential for efficient cytotoxic capacity and migration of NK cells.

Filamin A Phosphorylation at Serine 2152 by the Serine/Threonine Kinase Ndr2 Controls TCR-Induced LFA-1 Activation in T Cells.

The integrin LFA-1 (CD11a/CD18) plays a critical role in the interaction of T cells with antigen presenting cells (APCs) to promote lymphocyte differentiation and proliferation. This integrin can be present either in a closed or in an open active conformation and its activation upon T-cell receptor (TCR) stimulation is a critical step to allow interaction with APCs. In this study we demonstrate that the serine/threonine kinase Ndr2 is critically involved in the initiation of TCR-mediated LFA-1 activation (open conformation) in T cells. Ndr2 itself becomes activated upon TCR stimulation and phosphorylates the intracellular integrin binding partner Filamin A (FLNa) at serine 2152. This phosphorylation promotes the dissociation of FLNa from LFA-1, allowing for a subsequent association of Talin and Kindlin-3 which both stabilize the open conformation of LFA-1. Our data suggest that Ndr2 activation is a crucial step to initiate TCR-mediated LFA-1 activation in T cells.

Combined Treatment with Zinc Aspartate and Intravenous Immunoglobulins (IVIGs) Ameliorates Experimental Autoimmune Encephalomyelitis (EAE).

Intravenous immunoglobulins (IVIGs) are widely used in replacement therapy of primary and secondary immunodeficiency disorders and in approved autoimmune indications. In addition, IVIG application is used off-label for treatment of other autoimmune diseases, e.g., multiple sclerosis (MS), an inflammatory autoimmune disorder with a clear T cell-mediated immune pathogenesis. The trace element zinc is shown to play a regulatory role in the maintenance of immune functions. Changes of zinc homeostasis affect both the innate and the adaptive immune system. On one hand, therapeutic zinc supplementation can normalize impaired immune functions due to zinc deficiency. On the other hand, therapeutic zinc supplementation is under consideration as a possible option to treat T cell-mediated autoimmune diseases. The aim of the present study was to investigate the influence of IVIG (Octagam®), zinc aspartate (Unizink®), and the combined application of both preparations in the experimental autoimmune encephalomyelitis (EAE), the animal model of MS. Therapeutic intraperitoneal application of zinc aspartate significantly diminished clinical signs during the relapsing-remitting phase of EAE in SJL/J mice. In contrast, IVIG given in a therapeutic manner did not influence the course of EAE. Interestingly, the combined application of both, IVIG and zinc aspartate, significantly reduced the severity of the disease during the acute and the relapsing-remitting phase of the EAE. Our data suggest that the combination of IVIG and zinc aspartate may have beneficial effects in autoimmune diseases, like MS. Further studies should verify the benefit of a controlled immunosuppressive therapy with IVIG and zinc for such diseases.