A Phosphatase-Mimetic Nano-Stabilizer of Mast Cells for Long-Term Prevention of Allergic Disease

Allergic diseases are pathological immune responses with significant morbidity, which are closely associated with allergic mediators as released by allergen-stimulated mast cells (MCs). Prophylactic stabilization of MCs is regarded as a practical approach to prevent allergic diseases. However, most of the existing small molecular MC stabilizers exhibit a narrow therapeutic time window, failing to provide long-term prevention of allergic diseases. Herein, ceria nanoparticle (CeNP-) based phosphatase-mimetic nano-stabilizers (PMNSs) with a long-term therapeutic time window are developed for allergic disease prevention. By virtue of the regenerable catalytic hotspots of oxygen vacancies on the surface of CeNPs, PMNSs exhibit sustainable phosphatase-mimetic activity to dephosphorylate phosphoproteins in allergen-stimulated MCs. Consequently, PMNSs constantly modulate intracellular phospho-signaling cascades of MCs to inhibit the degranulation of allergic mediators, which prevents the initiation of allergic mediator-associated pathological responses, eventually providing protection against allergic diseases with a long-term therapeutic time window.

Immunological and clinical characteristics of latent autoimmune diabetes in the elderly

BACKGROUND

Latent autoimmune diabetes in adults (LADA) is determined by both a noninsulin-dependent clinical presentation and an autoimmune pathogenic process. Glutamic acid decarboxylase antibody (GADA) constitutes the most important marker, although IA-2A and ZnT8A also define LADA presentation. Type 2 diabetes mellitus (T2DM) is the most prevalent type particularly over 65 years old. Studies about autoimmunity in this age group are scarce.

OBJECTIVE

The aim of this work was to determine whether three autoantibodies for diabetes autoimmunity were present in elderly T2DM patients, and to assess the distinctive clinical features of autoantibody-positive patients.

RESEARCH DESIGN AND METHODS

We recruited 153 patients with diabetes with onset of diabetes after 65 years of age and a BMI under 30 kg/m² .

RESULTS

The prevalence of at least one of the autoantibodies was 15.68% (24/153). The most prevalent autoantibody was GADA with 8.49% (13/153), followed by ZnT8A with 6.50% (10/153) and IA2A with 1.96% (3/153). The autoimmunity-positive group presented higher HbA1c (7.01 ± 1.98 vs 6.35 ± 1.01; P = 0.007) and more prevalent insulin therapy (25% vs 10.85%; P = 0.047). GADA-positive patients with diabetes presented higher FPG (7.79 ± 3.79 mmol/L vs 6.43 ± 1.6 mmol/L; P = 0.014) and insulin therapy more frequently (46% vs 10.71%; p = 0.015). GADA titre levels in the individuals with BMI under 27 kg/m² were higher (35.00 ± 4.20) than those in the group with BMI over 27 kg/m² (8.83 ± 3.041; P = 0.0005).

CONCLUSION

Autoantibodies GADA and Znt8A may be useful markers in identifying a subgroup of older patients with a clinical presentation of diabetes which could be characterized as latent autoimmune diabetes in the elderly.

Identification of protective protein antigens for vaccination against Streptococcus dysgalactiae in cobia (Rachycentron canadum)

Streptococcus dysgalactiae is considered a causative agent of severe infection and economic loss for the cobia industry in Taiwan. In this study, protective antigens of this pathogenic bacterium were identified and screened in cobia (Rachycentron canadum). Outer surface proteins (OMPs) of this pathogen were extracted using mutanolysin digestion. Immunogenic targets were detected by western blot and then subjected to peptide sequencing using NanoLC-MS/MS. Two surface proteins, namely phosphoenolpyruvate protein phosphotransferase (PtsA) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), showed strong reactions with cobia antisera against S. dysgalactiae. Recombinant proteins were produced in Escherichia coli cells and their protective efficacies were investigated in cobia. Fish immunised with recombinant proteins, rPtsA + ISA (ISA 763 AVG) and rGAPDH + ISA, elicited higher levels of specific antibody responses against the recombinant proteins and had high levels of lysozyme activity. Notably, vaccinated fish were protected from lethal challenge with relative percentage of survival (RPS) values for rPtsA + ISA and rGAPDH + ISA groups being 91.67% and 83.33%, while 0% RPS value was found in both ISA injected and control groups. The results presented in the study demonstrate that the GAPDH and PtsA are promising vaccine candidates for preventing S. dysgalactiae disease in cobia.

Endoplasmic reticulum stress-induced apoptosis accompanies enhanced expression of multiple inositol polyphosphate phosphatase 1 (Minpp1): a possible role for Minpp1 in cellular stress response

Inositol polyphosphates represent a group of differentially phosphorylated inositol metabolites, many of which are implicated to regulate diverse cellular processes such as calcium mobilization, vesicular trafficking, differentiation, apoptosis, etc. The metabolic network of these compounds is complex and tightly regulated by various kinases and phosphatases present predominantly in the cytosol. Multiple inositol polyphosphate phosphatase 1 (Minpp1) is the only known endoplasmic reticulum (ER) luminal enzyme that hydrolyzes various inositol polyphosphates in vitro as well as in vivo conditions. However, access of the Minpp1 to cytosolic substrates has not yet been demonstrated clearly and hence its physiological function. In this study, we examined a potential role for Minpp1 in ER stress-induced apoptosis. We generated a custom antibody and characterized its specificity to study the expression of Minpp1 protein in multiple mammalian cells under experimentally induced cellular stress conditions. Our results demonstrate a significant increase in the expression of Minpp1 in response to a variety of cellular stress conditions. The protein expression was corroborated with the expression of its mRNA and enzymatic activity. Further, in an attempt to link the role of Minpp1 to apoptotic stress, we studied the effect of Minpp1 expression on apoptosis following silencing of the Minpp1 gene by its specific siRNA. Our results suggest an attenuation of apoptotic parameters following knockdown of Minpp1. Thus, in addition to its known role in inositol polyphosphate metabolism, we have identified a novel role for Minpp1 as a stress-responsive protein. In summary, our results provide, for the first time, a probable link between ER stress-induced apoptosis and Minpp1 expression.

Human genome-wide RNAi screen identifies an essential role for inositol pyrophosphates in Type-I interferon response

The pattern recognition receptor RIG-I is critical for Type-I interferon production. However, the global regulation of RIG-I signaling is only partially understood. Using a human genome-wide RNAi-screen, we identified 226 novel regulatory proteins of RIG-I mediated interferon-β production. Furthermore, the screen identified a metabolic pathway that synthesizes the inositol pyrophosphate 1-IP7 as a previously unrecognized positive regulator of interferon production. Detailed genetic and biochemical experiments demonstrated that the kinase activities of IPPK, PPIP5K1 and PPIP5K2 (which convert IP5 to1-IP7) were critical for both interferon induction, and the control of cellular infection by Sendai and influenza A viruses. Conversely, ectopically expressed inositol pyrophosphate-hydrolases DIPPs attenuated interferon transcription. Mechanistic experiments in intact cells revealed that the expression of IPPK, PPIP5K1 and PPIP5K2 was needed for the phosphorylation and activation of IRF3, a transcription factor for interferon. The addition of purified individual inositol pyrophosphates to a cell free reconstituted RIG-I signaling assay further identified 1-IP7 as an essential component required for IRF3 activation. The inositol pyrophosphate may act by β-phosphoryl transfer, since its action was not recapitulated by a synthetic phosphonoacetate analogue of 1-IP7. This study thus identified several novel regulators of RIG-I, and a new role for inositol pyrophosphates in augmenting innate immune responses to viral infection that may have therapeutic applications.

The innate immune system is critical for viral infection control by host organisms. The type I interferons are a family of major antiviral cytokines produced upon the activation of innate immune pattern recognition receptors (PRRs) by viruses. The RIG-I is a major PRR that uniquely detects RNA viruses within the cytoplasm. In this study, we aimed to discover cellular genes and pathways that play regulatory roles in the transcriptional induction of type I interferon-β (IFNβ). Using a human genome wide RNA interference (RNAi) screening, we identified 226 genes whose expression is important for proper IFNβ production. Through bioinformatics-based mining of the RNAi screen results, we identified that the cellular pathway synthesizing inositol pyrophosphates, a class of inositol phosphates with high-energy diphosphates, is a key positive regulator of RIG-I mediated IFNβ production. The kinases IPPK, PPIP5K1 and PPIP5K2, that synthesize inositol pyrophosphate 1-IP7, regulated IFNβ response in a catalytically dependent manner. Mechanistic studies identified that 1-IP7 synthesis pathway was needed for efficient phosphorylation of IRF3. The DIPP family of inositol pyrophosphate hydrolases negatively regulated the IFNβ response, upon ectopic expression. In summary, this study generated a global view of the regulation of RIG-I signaling, and identified inositol pyrophosphates as important regulators of antiviral response.

Allogeneic T cell responses are regulated by a specific miRNA-mRNA network

Donor T cells that respond to host alloantigens following allogeneic bone marrow transplantation (BMT) induce graft-versus-host (GVH) responses, but their molecular landscape is not well understood. MicroRNAs (miRNAs) regulate gene (mRNA) expression and fine-tune the molecular responses of T cells. We stimulated naive T cells with either allogeneic or nonspecific stimuli and used argonaute cross-linked immunoprecipitation (CLIP) with subsequent ChIP microarray analyses to profile miR responses and their direct mRNA targets. We identified a unique expression pattern of miRs and mRNAs following the allostimulation of T cells and a high correlation between the expression of the identified miRs and a reduction of their mRNA targets. miRs and mRNAs that were predicted to be differentially regulated in allogeneic T cells compared with nonspecifically stimulated T cells were validated in vitro. These analyses identified wings apart-like homolog (Wapal) and synaptojanin 1 (Synj1) as potential regulators of allogeneic T cell responses. The expression of these molecular targets in vivo was confirmed in MHC-mismatched experimental BMT. Targeted silencing of either Wapal or Synj1 prevented the development of GVH response, confirming a role for these regulators in allogeneic T cell responses. Thus, this genome-wide analysis of miRNA-mRNA interactions identifies previously unrecognized molecular regulators of T cell responses.

Immunization of Mastomys coucha with Brugia malayi recombinant trehalose-6-phosphate phosphatase results in significant protection against homologous challenge infection

Development of a vaccine to prevent or reduce parasite development in lymphatic filariasis would be a complementary approach to existing chemotherapeutic tools. Trehalose-6-phosphate phosphatase of Brugia malayi (Bm-TPP) represents an attractive vaccine target due to its absence in mammals, prevalence in the major life stages of the parasite and immunoreactivity with human bancroftian antibodies, especially from endemic normal subjects. We have recently reported on the cloning, expression, purification and biochemical characterization of this vital enzyme of B. malayi. In the present study, immunoprophylactic evaluation of Bm-TPP was carried out against B. malayi larval challenge in a susceptible host Mastomys coucha and the protective ability of the recombinant protein was evaluated by observing the adverse effects on microfilarial density and adult worm establishment. Immunization caused 78.4% decrease in microfilaremia and 71.04% reduction in the adult worm establishment along with sterilization of 70.06% of the recovered live females. The recombinant protein elicited a mixed Th1/Th2 type of protective immune response as evidenced by the generation of both pro- and anti-inflammatory cytokines IL-2, IFN-γ, TNF-α, IL-4 and an increased production of antibody isotypes IgG1, IgG2a, IgG2b and IgA. Thus immunization with Bm-TPP conferred considerable protection against B. malayi establishment by engendering a long-lasting effective immune response and therefore emerges as a potential vaccine candidate against lymphatic filariasis (LF).

Host protein BSL1 associates with Phytophthora infestans RXLR effector AVR2 and the Solanum demissum Immune receptor R2 to mediate disease resistance

Plant pathogens secrete effector proteins to modulate plant immunity and promote host colonization. Plant nucleotide binding leucine-rich repeat (NB-LRR) immunoreceptors recognize specific pathogen effectors directly or indirectly. Little is known about how NB-LRR proteins recognize effectors of filamentous plant pathogens, such as Phytophthora infestans. AVR2 belongs to a family of 13 sequence-divergent P. infestans RXLR effectors that are differentially recognized by members of the R2 NB-LRR family in Solanum demissum. We report that the putative plant phosphatase BSU-LIKE PROTEIN1 (BSL1) is required for R2-mediated perception of AVR2 and resistance to P. infestans. AVR2 associates with BSL1 and mediates the interaction of BSL1 with R2 in planta, possibly through the formation of a ternary complex. Strains of P. infestans that are virulent on R2 potatoes express an unrecognized form, Avr2-like (referred to as A2l). A2L can still interact with BSL1 but does not promote the association of BSL1 with R2. Our findings show that recognition of the P. infestans AVR2 effector by the NB-LRR protein R2 requires the putative phosphatase BSL1. This reveals that, similar to effectors of phytopathogenic bacteria, recognition of filamentous pathogen effectors can be mediated via a host protein that interacts with both the effector and the NB-LRR immunoreceptor.

Helicobacter pylori versus the host: remodeling of the bacterial outer membrane is required for survival in the gastric mucosa

Modification of bacterial surface structures, such as the lipid A portion of lipopolysaccharide (LPS), is used by many pathogenic bacteria to help evade the host innate immune response. Helicobacter pylori, a gram-negative bacterium capable of chronic colonization of the human stomach, modifies its lipid A by removal of phosphate groups from the 1- and 4'-positions of the lipid A backbone. In this study, we identify the enzyme responsible for dephosphorylation of the lipid A 4'-phosphate group in H. pylori, Jhp1487 (LpxF). To ascertain the role these modifications play in the pathogenesis of H. pylori, we created mutants in lpxE (1-phosphatase), lpxF (4'-phosphatase) and a double lpxE/F mutant. Analysis of lipid A isolated from lpxE and lpxF mutants revealed lipid A species with a 1 or 4'-phosphate group, respectively while the double lpxE/F mutant revealed a bis-phosphorylated lipid A. Mutants lacking lpxE, lpxF, or lpxE/F show a 16, 360 and 1020 fold increase in sensitivity to the cationic antimicrobial peptide polymyxin B, respectively. Moreover, a similar loss of resistance is seen against a variety of CAMPs found in the human body including LL37, β-defensin 2, and P-113. Using a fluorescent derivative of polymyxin we demonstrate that, unlike wild type bacteria, polymyxin readily associates with the lpxE/F mutant. Presumably, the increase in the negative charge of H. pylori LPS allows for binding of the peptide to the bacterial surface. Interestingly, the action of LpxE and LpxF was shown to decrease recognition of Helicobacter LPS by the innate immune receptor, Toll-like Receptor 4. Furthermore, lpxE/F mutants were unable to colonize the gastric mucosa of C57BL/6J and C57BL/6J tlr4 -/- mice when compared to wild type H. pylori. Our results demonstrate that dephosphorylation of the lipid A domain of H. pylori LPS by LpxE and LpxF is key to its ability to colonize a mammalian host.

Role of SHIP-1 in the adaptive immune responses to aeroallergen in the airway

Background

Th2-dominated inflammatory response in the airway is an integral component in the pathogenesis of allergic asthma. Accumulating evidence supports the notion that the phosphoinositide 3-kinase (PI3K) pathway is involved in the process. We previously reported that SHIP-1, a negative regulator of the PI3K pathway, is essential in maintaining lung immunohomeostasis, potentially through regulation of innate immune cells. However, the function of SHIP-1 in adaptive immune response in the lung has not been defined. We sought to determine the role of SHIP-1 in adaptive immunity in response to aeroallergen stimulation in the airway.

Methodology/Principal Findings

SHIP-1 knockout (SHIP-1^−/−) mice on BALB/c background were immunized with ovalbumin (OVA) plus aluminum hydroxide, a strong Th2-inducing immunization, and challenged with OVA. Airway and lung inflammation, immunoglobulin response, Th2 cytokine production and lymphocyte response were analyzed and compared with wild type mice. Even though there was mild spontaneous inflammation in the lung at baseline, SHIP-1^−/− mice showed altered responses, including less cell infiltration around the airways but more in the parenchyma, less mucus production, decreased Th2 cytokine production, and diminished serum OVA-specific IgE, IgG1, but not IgG2a. Naïve and OVA sensitized SHIP-1^−/− T cells produced a lower amount of IL-4. In vitro differentiated SHIP-1^−/− Th2 cells produced less IL-4 compared to wild type Th2 cells upon T cell receptor stimulation.

Conclusions/Significance

These findings indicate that, in contrast to its role as a negative regulator in the innate immune cells, SHIP-1 acts as a positive regulator in Th2 cells in the adaptive immune response to aeroallergen. Thus any potential manipulation of SHIP-1 activity should be adjusted according to the specific immune response.

Concerted action of Helios and Ikaros controls the expression of the inositol 5-phosphatase SHIP

Ikaros family transcription factors have a key role in lymphoid development, and their aberrant function contributes to a multitude of lymphoid malignancies. Ikaros and Helios bind to similar DNA sequences, and Helios associates with Ikaros-containing chromatin remodeling complexes. Previously, we have shown that loss of Ikaros leads to diminished BCR-signaling strength. In this study, we describe a Helios-deficient chicken DT40 B-cell line with a BCR signaling phenotype that is the opposite to that of Ikaros-deficient cells. In contrast to Ikaros-deficient cells, Helios(-/-) B cells exhibit increased calcium release to the cytoplasm after BCR crosslinking, but diminished BCR-induced phosphorylation of signaling molecules. The inositol 5-phosphatase SHIP, an important regulator in several signaling pathways, is differentially expressed in Ikaros- and Helios-deficient cells. In the absence of Ikaros, SHIP is upregulated, whereas Helios deficiency leads to the downregulation of SHIP expression. We also show with ChIP that Ikaros binds to the promoter of the INPP5D gene-encoding SHIP. Considering the critical role of SHIP in the BCR signaling pathway, our findings provide insight into the mechanism of how both Helios and Ikaros are involved in the regulation of BCR signaling.

Regulation of the mast cell response to the type 1 Fc epsilon receptor

The type I Fc epsilon receptor (Fc epsilon RI) is one of the better understood members of its class and is central to the immunological activation of mast cells and basophils, the key players in immunoglobulin E (IgE)-dependent immediate hypersensitivity. This review provides background information on several distinct regulatory mechanisms controlling this receptor's stimulus-response coupling network. First, we review the current understanding of this network's operation, and then we focus on the inhibitory regulatory mechanisms. In particular, we discuss the different known cytosolic molecules (e.g. kinases, phosphatases, and adapters) as well as cell membrane proteins involved in negatively regulating the Fc epsilon RI-induced secretory responses. Knowledge of this field is developing at a fast rate, as new proteins endowed with regulatory functions are still being discovered. Our understanding of the complex networks by which these proteins exert regulation is limited. Although the scope of this review does not include addressing several important biochemical and biophysical aspects of the regulatory mechanisms, it does provide general insights into a central field in immunology.

Identification of HLA-CW3, GNAS and IMPA as cytotoxic T-lymphocyte (CTL) target antigens using an allogeneic mixed lymphocyte tumor cell culture (MLTC) system and subsequent cDNA library screening

Allogeneic mixed lymphocyte tumor cell cultures (MLTCs) were established using lymphocytes from non-small-cell lung cancer (NSCLC) patient UKY-53 and HLA-A2+ NSCLC tumor cells (UKY-29). The tumor cells expressed the lymphocyte costimulatory molecule CD80 (UKY29.7). Cytolytic activity showed the cytotoxic T-lymphocytes (CTL) lysed UKY-29, but not K562 or Daudi. The CTL also lysed: HLA-A2+ and -A24+ tumor cell lines from a number of tumor histologies. The CTL also lysed Epstein Barr virus transformed (EBV) B-cells, UKY-29EBV, autologous to the stimulating cell line, UKY29TC. These data suggested the presence of both tumor-specific and allogeneic reactivities in the bulk CTL population. Subsequent cDNA cloning analysis and sequencing demonstrated that the bulk CTL population was recognizing: (i) allogeneic target HLA-CW3, and two minor histocompatibility antigens; (ii) guanine nucleotide-binding protein, G(S) (GNAS), and (iii) inositol myophosphatase (IMPA). All three antigens, we believe, were restricted by HLA-A2. Whereas the system described was initially intended to identify tumor-associated antigens recognized by CTL, the nature of the allogeneic system provides a unique opportunity for the identification of epitopes that confer both allo and minor antigen recognition.

Trehalose-6-phosphate Phosphatase from Mycobacterium tuberculosis induces humoral and cellular immune responses

Trehalose-6-phosphate phosphatase is an enzyme strictly essential for the growth of mycobacteria. Subcellular fractionation of Mycobacterium tuberculosis and M. bovis bacillus Calmette-Guérin (BCG) located the trehalose-6-phosphate phosphatase in the cell wall and membrane fractions. Trehalose-6-phosphate phosphatase induced an increased Th1-type immune response in mice, characterized by an elevated level of interferon-gamma in antigen-stimulated splenocyte culture and a strong IgG2a antibody response. The trehalose-6-phosphate phosphatase was recognized by the sera of tuberculosis patients and BCG-vaccinated donors. The mycobacterial trehalose-6-phosphate phosphatase is an immunodominant antigen, and it may be a candidate for vaccine development for the control of tuberculosis.

Cutting Edge: Acute and chronic exposure of immature B cells to antigen leads to impaired homing and SHIP1-dependent reduction in stromal cell-derived factor-1 responsiveness

An encounter of B cells with cognate self Ags in the periphery can lead to anergy, a condition characterized by altered anatomical localization, shortened life span, and refractility to Ag stimulation. We recently reported that an immature B cell encounter with cognate self-Ag in the bone marrow can also lead to anergy. In this study we show that anergic as well as acutely Ag-stimulated immature B cells are defective in stromal cell-derived factor-1 (SDF-1)-induced calcium mobilization and migration and do not localize to bone marrow following adoptive transfer. This hyporesponsiveness does not involve CXCR4 modulation. However, BCR signal-mediated hyporesponsiveness to SDF-1 is associated with phosphorylation of the 5-inositol phosphatase SHIP1 and requires SHIP1 expression. Therefore, an encounter with cognate Ag may, by preventing SDF-1-induced phosphatidylinositol 3,4,5-triphosphate accumulation, trigger premature emigration of immature B cells from bone marrow.

Induced SHIP deficiency expands myeloid regulatory cells and abrogates graft-versus-host disease

Graft-vs-host disease (GVHD) is the leading cause of treatment-related death in allogeneic bone marrow (BM) transplantation. Immunosuppressive strategies to control GVHD are only partially effective and often lead to life-threatening infections. We previously showed that engraftment of MHC-mismatched BM is enhanced and GVHD abrogated in recipients homozygous for a germline SHIP mutation. In this study, we report the development of a genetic model in which SHIP deficiency can be induced in adult mice. Using this model, we show that the induction of SHIP deficiency in adult mice leads to a rapid and significant expansion of myeloid suppressor cells in peripheral lymphoid tissues. Consistent with expansion of myeloid suppressor cells, splenocytes and lymph node cells from adult mice with induced SHIP deficiency are significantly compromised in their ability to prime allogeneic T cell responses. These results demonstrate that SHIP regulates homeostatic signals for these immunoregulatory cells in adult physiology. Consistent with these findings, induction of SHIP deficiency before receiving a T cell-replete BM graft abrogates acute GVHD. These findings indicate strategies that target SHIP could increase the efficacy and utility of allogeneic BM transplantation, and thereby provide a curative therapy for a wide spectrum of human diseases.

Clonorchis sinensis: expression, characterization, immunolocalization and serological reactivity of one excretory/secretory antigen-LPAP homologue

From a Clonorchis sinensis adult cDNA plasmid library, a cDNA clone encoding a novel lysophosphatidic acid phosphatase (LPAP) homologue was isolated. The predicted molecular weight of putative protein was 48.8 kDa and the deduced amino acid sequence had 45%, 32%, and 29% identity with LPAP of Schistosoma japonicum, Danio rerio, and Homo sapiens, respectively. Prediction of signal peptide and Western blot analysis indicated that the CsLPAP homologue was an excretory-secretory antigen (ES antigen) of C. sinensis. Immunostaining revealed that the CsLPAP was markedly localized in the intestinal cecum, seminal receptacle and eggs of the adult worm. The recombinant CsLPAP showed slightly higher sensitivity (82.14%) and specificity (85.86%) than the crude worm antigen by enzyme-linked immunosorbent assay (ELISA), a result which suggested that the recombinant antigen might be valuable in the serodiagnosis of human clonorchiasis.

SHIP-deficient mice provide insights into the regulation of dendritic cell development and function

OBJECTIVE

Dendritic cells (DC) play a critical role in establishment and maintenance of central and peripheral tolerance. Despite intensive research, our knowledge of the molecular mechanisms regulating DC development and function is limited, thus hindering our ability to generate appropriate DC populations for manipulating immune tolerance. We utilized mice deficient in the SH2-containing inositol-5-phosphatase (SHIP) to examine the role of cytokine signaling in DC development and function.

METHODS

We analyzed the phenotype of both primary and bone marrow (BM)-derived DC (BMDC) using flow cytometry. In addition, cytokine production was measured using cytometric bead arrays and the ability of DC to induce allogeneic T-cell proliferation was assessed using thymidine incorporation assays.

RESULTS

We demonstrated that spleen DC isolated from SHIP-deficient mice are increased in number and have an altered phenotype. In vitro analyses revealed that SHIP-deficient BM cells give rise to a higher frequency of myeloid, but not plasmacytoid, DC due to both an increased progenitor frequency and enhanced cytokine sensitivity. The BMDC exhibit an altered phenotype that correlates with a reduced capacity to induce allogeneic T-cell proliferation. Addition of interleukin-6 to WT BM cultures during DC differentiation partially induces a KO phenotype.

CONCLUSION

These studies suggest that myeloid and plasmacytoid DC progenitors are differentially sensitive to signaling pathways in which SHIP is involved. Moreover, they suggest that interleukin-6 may have an important role in regulating the phenotype and function of myeloid DC.

Anti-endothelial antibodies and neuropsychiatric systemic lupus erythematosus

The pathogenesis of neuropsychiatric systemic lupus erythematosus (NPSLE) has been attributed to autoantibody-mediated neural dysfunction, vasculopathy, and coagulopathy. Several autoantibodies specificities have been reported in serum and cerebrospinal fluid of NPSLE patients (i.e., antineuronal, antiribosomal P proteins, antiglial fibrillary acidic proteins, antiphospholipid, and anti-endothelial antibodies). We have recently demonstrated an association between serum anti-endothelial antibodies and psychosis or depression in patients with SLE. Subsequently, by screening a cDNA library from human umbilical artery endothelial cells with serum from a SLE patient with psychosis, one positive strongly reactive clone was identified encoding the C-terminal region (C-ter) of Nedd5, an intracytoplasmatic protein of the septin family. Anti-Nedd5 antibodies have been found significantly associated with psychiatric manifestations in SLE patients, strengthening the view of a possible implication of autoantibodies in the development of psychiatric disorders.

A mitotic septin scaffold required for Mammalian chromosome congression and segregation

Coordination of cytokinesis with chromosome congression and segregation is critical for proper cell division, but the mechanism is unknown. Here, septins, a conserved family of polymerizing guanosine triphosphate-binding proteins, localized to the metaphase plate during mitosis. Septin depletion resulted in chromosome loss from the metaphase plate, lack of chromosome segregation and spindle elongation, and incomplete cytokinesis upon delayed mitotic exit. These defects correlated with loss of the mitotic motor and the checkpoint regulator centromere-associated protein E (CENP-E) from the kinetochores of congressing chromosomes. Mammalian septins may thus form a mitotic scaffold for CENP-E and other effectors to coordinate cytokinesis with chromosome congression and segregation.

PTEN permits acute increases in D3-phosphoinositide levels following TCR stimulation but inhibits distal signaling events by reducing the basal activity of Akt

Phosphoinositide 3-kinase (PI3K) is important in TCR signaling. PI3K generates phosphatidylinositol 3, 4, 5-trisphosphate (PI-3,4,5-P3), which regulates membrane localization and/or activity of multiple signaling proteins. PTEN (phosphatase and tensin homologue deleted on chromosome 10) opposes PI3K, reversing this reaction. Maintaining the balance between these two enzymes is important for normal T cell function. Here we use the PTEN-null Jurkat T cell line to address the role of PTEN in modulating proximal and distal TCR-signaling events. PTEN expression at levels that restored low basal Akt phosphorylation (an indicator of PI-3,4,5-P3 levels), but which were not themselves cytotoxic, had minimal effect on TCR-stimulated activation of phospholipase Cgamma1 and Ca2+ flux, but reduced the duration of extracellular signal-regulated kinase (Erk) activation. Distal signaling events, including nuclear factor of activated T cells (NFAT) activation, CD69 expression and IL-2 production, were all inhibited by PTEN expression. Notably, PTEN did not block TCR-stimulated PI-3,4,5-P3 accumulation. The effect of PTEN on distal TCR signaling events was strongly correlated with the loss of the constitutive Akt activation and glycogen synthase kinase-3 (GSK3) inhibition that is typical of Jurkat cells, and could be reversed by expression of activated Akt or pharmacologic inhibition of GSK3. These results suggest that PTEN acts in T cells primarily to control basal PI-3,4,5-P3 levels, rather than opposing PI3K acutely during TCR stimulation.

SHIP Down-Regulates FcεR1-Induced Degranulation at Supraoptimal IgE or Antigen Levels

Cross-linking of the IgE-loaded high-affinity IgE receptor (FcepsilonR1) by multivalent Ags results in mast cell activation and subsequent release of multiple proinflammatory mediators. The dose-response curve for FcepsilonR1-mediated degranulation is bell-shaped, regardless of whether the IgE or the Ag concentration is varied. Although overall calcium influx follows this bell-shaped curve, intracellular calcium release continues to increase at supraoptimal IgE or Ag concentrations. As well, overall calcium mobilization adopts more transient kinetics when stimulations are conducted with supraoptimal instead of optimal Ag concentrations. Moreover, certain early signaling events continue to increase whereas degranulation drops under supraoptimal conditions. We identified SHIP, possibly in association with the FcepsilonR1 beta-chain, as a critical negative regulator acting within the inhibitory (supraoptimal) region of the dose-response curve that shifts the kinetics of calcium mobilization from a sustained to a transient response. Consistent with this, we found that degranulation of SHIP-deficient murine bone marrow-derived mast cells was not significantly reduced at supraoptimal Ag levels. A potential mediator of SHIP action, Bruton's tyrosine kinase, did not seem to play a role within the supraoptimal suppression of degranulation. Interestingly, SHIP was found to colocalize with the actin cytoskeleton (which has been shown previously to mediate the inhibition of degranulation at supraoptimal Ag doses). These results suggest that SHIP, together with other negative regulators, restrains bone marrow-derived mast cell activation at supraoptimal IgE or Ag concentrations in concert with the actin cytoskeleton.

Pyridoxal phosphatase is a novel cancer autoantigen in the central nervous system

Autoantibodies against many proteins are common in sera from patients with various types of cancer. These antibodies are sometimes involved in the development of conditions associated with cancer, such as paraneoplastic neurologic disorders. We used a human brain cDNA expression library and serum from a paraneoplastic neurologic disorder patient to search for new autoantigens in the nervous system. Pyridoxal phosphatase was identified as a novel autoantigen. Expression studies showed that pyridoxal phosphatase was strongly expressed in various parts of the central nervous system. Sera contained antibodies against pyridoxal phosphatase in 22 of 243 (9.1%) patients with lung cancer and eight of 113 (7.1%) with other forms of cancer vs two of 88 (2.3%) healthy control subjects. In addition, 2-4% of patients with different autoimmune diseases had autoantibodies against pyridoxal phosphatase. None of the antipyridoxal phosphatase-positive patients were known to have a paraneoplastic neurologic disorder. Hence, autoantibodies against pyridoxal phosphatase correlate with cancer but not necessarily with the subset of patients with paraneoplastic neurological disorders although serum from such a patient was used to screen the cDNA library. This study showed that yet another enzyme involved in pyridoxal 5'-phosphate metabolism is an autoantigen. Thus, pyridoxal 5'-phosphate seems to be a common denominator for autoantigens involved in autoimmune diseases.

LPS-induced upregulation of SHIP is essential for endotoxin tolerance

An initial exposure to lipopolysaccharide (LPS) induces a transient state of hyporesponsiveness to a subsequent challenge with LPS. The mechanism underlying this phenomenon, termed endotoxin tolerance, remains poorly understood despite a recent resurgence of interest in this area. We demonstrate herein that SHIP(-/-) bone marrow-derived macrophages (BMmphis) and mast cells (BMMCs) do not display endotoxin tolerance. Moreover, an initial LPS treatment of wild-type BMmphis or BMMCs increases the level of SHIP, but not SHIP2 or PTEN, and this increase is critical for the hyporesponsiveness to subsequent LPS stimulation. Interestingly, this increase in SHIP protein is mediated by the LPS-induced production of autocrine-acting TGFbeta and neutralizing antibodies to TGFbeta block LPS-induced endotoxin tolerance. In vivo studies with SHIP(+/+) and SHIP(-/-) mice confirm these in vitro findings and show a correlation between the duration of endotoxin tolerance and elevated SHIP levels.

African swine fever virus proteins involved in evading host defence systems

African swine fever virus (ASFV) can cause an acutely fatal haemorrhagic fever in domestic pigs although in its natural hosts, warthogs, bushpigs and the soft tick vector, Ornithodoros moubata, ASFV causes inapparent persistent infections. The virus is a large, cytoplasmic, double-stranded DNA virus which has a tropism for macrophages. As it is the only member of the Asfarviridae family, ASFV encodes many novel genes not encoded by other virus families. The ability of the virus to persist in its natural hosts and in domestic pigs, which recover from infection with less virulent isolates, shows that the virus has effective mechanisms to evade host defence systems. This review focuses on recent progress made in understanding the function of ASFV-encoded proteins, which are involved in modulating the host response to infection. Growing evidence suggests that a major strategy used by the virus is to modulate signalling pathways in infected macrophages, thus interfering with the expression of a large number of immunomodulatory genes. One potent immunomodulatory protein, A238L, inhibits both activation of the host NFkappaB transcription factor and inhibits calcineurin phosphatase activity. Calcineurin-dependent pathways, including activation of the NFAT transcription factor, are therefore inhibited. Another ASFV-encoded protein, CD2v, resembles the host CD2 protein, which is expressed on T cells and NK cells. This virus protein causes the adsorption of red blood cells around virus-infected cells and extracellular virus particles. Expression of the CD2v protein aids virus dissemination in pigs and the protein also has a role in impairing bystander lymphocyte function. This may be mediated either by a direct interaction of CD2v extracellular domain with ligands on lymphocytes or by an indirect mechanism involving interaction of the CD2v cytoplasmic tail with host proteins involved in signalling or trafficking pathways. Two ASFV proteins, an IAP and a Bcl2 homologue, inhibit apoptosis in infected cells and thus facilitate production of progeny virions. The prediction is that half to two-thirds of the approximately 150 genes encoded by ASFV are not essential for replication in cells but have an important role for virus survival and transmission in its hosts. These genes provide an untapped repository, and will be valuable tools for deciphering not only how the virus manipulates the host response to infection to avoid elimination, but also useful for understanding important host anti-viral mechanisms. In addition, they may provide leads for discovery of novel immunomodulatory drugs.

The role of PTEN in allergic inflammation

Bronchial asthma is a chronic inflammatory disease of the airways, characterized by airway eosinophilia, goblet cell hyperplasia with mucus hyper-secretion, and hyper-responsiveness to inhaled allergens and to non-specific stimuli. Eosinophil accumulation and subsequent activation in bronchial tissues play critical roles in the pathophysiology of bronchial asthma. Many inflammatory mediators attract and activate eosinophils via signal transduction pathways involving an enzyme phosphatidylinositol 3-kinase (PI3-kinase). Studies using wortmannin, a specific inhibitor of PI3-kinase, have revealed the involvement of PI3-kinase in the biochemical transduction of activation signals generated by many inflammatory mediators in eosinophils. Wortmannin prevents the development of airway inflammation, either by inhibiting the eosinophil infiltration of bronchial tissues or their activation on arrival. Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is part of a complex signaling system that affects a variety of important cell functions. PTEN opposes the action of PI3-kinase by dephosphorylating the signaling lipid phosphatidylinositol 3,4,5-triphosphate. Recently we have demonstrated that PTEN expression is diminished in airway epithelial cells of antigen-sensitized and -challenged mice. Administration of PI3-kinase inhibitors or adenoviruses carrying PTEN complementary DNA remarkably reduces eosinophil levels and inflammation. One likely mechanism for this reduction is PTEN-mediated eosinophil degranulation and suppression of interleukin (IL)-4 and IL-5. These findings indicate that use of PTEN may be a good therapeutic strategy for the management of allergic inflammation.

Co-aggregation of FcgammaRII with FcepsilonRI on human mast cells inhibits antigen-induced secretion and involves SHIP-Grb2-Dok complexes

Signaling through the high affinity IgE receptor FcepsilonRI on human basophils and rodent mast cells is decreased by co-aggregating these receptors to the low affinity IgG receptor FcgammaRII. We used a recently described fusion protein, GE2, which is composed of key portions of the human gamma1 and the human epsilon heavy chains, to dissect the mechanisms that lead to human mast cell and basophil inhibition through co-aggregation of FcgammaRII and FcepsilonRI. Unstimulated human mast cells derived from umbilical cord blood express the immunoreceptor tyrosine-based inhibitory motif-containing receptor FcgammaRII but not FcgammaRI or FcgammaRIII. Interaction of the mast cells with GE2 alone did not cause degranulation. Co-aggregating FcepsilonRI and FcgammaRII with GE2 1) significantly inhibited IgE-mediated histamine release, cytokine production, and Ca(2+) mobilization, 2) reduced the antigen-induced morphological changes associated with mast cell degranulation, 3) reduced the tyrosine phosphorylation of several cellular substrates, and 4) increased the tyrosine phosphorylation of the adapter protein downstream of kinase 1 (p62(dok); Dok), growth factor receptor-bound protein 2 (Grb2), and SH2 domain containing inositol 5-phosphatase (SHIP). Tyrosine phosphorylation of Dok was associated with increased binding to Grb2. Surprisingly, in non-stimulated cells, there were complexes of phosphorylated SHIP-Grb2-Dok that were lost upon IgE receptor activation but retained under conditions of Fcepsilon-Fcgamma co-aggregation. Finally, studies using mast cells from Dok-1 knock-out mice showed that IgE alone triggers degranulation supporting an inhibitory role for Dok degranulation. Our results demonstrate how human FcepsilonRI-mediated responses can be inhibited by co-aggregation with FcgammaRIIB and implicate Dok, SHIP, and Grb2 as key intermediates in regulating antigen-induced mediator release.

Autonomous SHIP-dependent FcγR signaling in pre-B cells leads to inhibition of cell migration and induction of cell death

Mature B cells express a single immunoglobulin Fc receptor, FcgammaRIIB, that functions to block downstream signaling by co-aggregated antigen receptors. Co-aggregation of receptors is essential because BCR activated kinases must phosphorylate FcgammaRIIB to recruit SHIP and mediate inhibitory signals. Pre-B cells also express FcgammaRIIB, but since they do not yet express antigen receptor, it is unclear when they are activated physiologically. Here, we demonstrate that aggregation of the FcR on pre-B cells leads to potent inhibitory signaling. Aggregation of the FcR alone leads to downstream effects including the induction of cell death and the blockade of SDF-1 induced migration. The biochemical circuitry that mediates this response is unique because although SHIP is required for this signaling and is phosphorylated upon receptor aggregation, this occurs in the absence of FcgammaRIIB phosphorylation. Results indicate that immune complexes may inhibit B cell production in the bone marrow by antigen non-specific mechanisms.

Synaptojanin 2 is recognized by HLA class II-restricted hairy cell leukemia-specific T cells

Hairy cell leukemia (HCL) is a chronic mature B-cell leukemia characterized by malignant B cells that have typical hairy protrusions. To characterize possible HCL-associated tumor antigens, we generated an HCL-specific and HLA class II (DPw4)-restricted proliferative CD4+ T-cell clone. To identify the target antigen of these T cells, we constructed a synthetic peptide library dedicated to bind HLA DPw4, and identified a mimicry epitope recognized by the T-cell clone. With this epitope, the recognition motif of the T-cell clone was deduced and a peptide of human synaptojanin 2 (Syn 2) was identified that stimulated the HCL-reactive T-cell clone. Both Northern and Western blot analyses showed that Syn 2 expression was increased in HCL samples compared to other B cells. Besides, the Syn 2-expressing cell line AML193, with the introduced restrictive HLA-DPw4 molecules, was recognized by the HCL-specific T-cell clone. These results indicate that Syn 2 is a target of autoreactive HCL-specific T cells. Since Syn 2 is a phosphatidylinositol 4,5-biphosphatase involved in cell growth and rearrangement of actin filaments, the increased Syn 2 expression may correlate with the disease etiology or the characteristic morphologic alterations caused by the disease.

Macrophages control the retention and trafficking of B lymphocytes in the splenic marginal zone

The marginal zone of the spleen is a precisely ordered region that contains specialized subsets of B lymphocytes and macrophages. Disruption of the negative signaling inositol phosphatase, SH2-containing inositol-5-phosphatase 1 (SHIP), results in the loss of marginal zone B cells (MZBs) with reorganization of marginal zone macrophages (MZMOs) to the red pulp of the spleen. This primary macrophage defect, as revealed by selectively depleting SHIP in myeloid cells shows that MZMOs are specifically required for the retention of MZBs. The MZMO phenotype was reverted in SHIP/Bruton's tyrosine kinase (Btk) double knockout mice, thus identifying the Btk activating pathway as an essential component being regulated by SHIP. Furthermore, we identified a direct interaction between the MARCO scavenger receptor on MZMOs and MZBs. Activation or disruption of this interaction results in MZB migration to the follicle. The migration of the MZMOs was further studied after the response to Staphylococcus aureus, which induced MZMOs to move into the red pulp while MZBs migrated into the follicular zone. The marginal zone is therefore a dynamic structure in which retention and trafficking of B cells requires specific macrophage-B cell interactions.

Involvement of PTEN in airway hyperresponsiveness and inflammation in bronchial asthma

Phosphatase and tensin homologue deleted on chromosome ten (PTEN) is part of a complex signaling system that affects a variety of important cell functions. PTEN blocks the action of PI3K by dephosphorylating the signaling lipid phosphatidylinositol 3,4,5-triphosphate. We have used a mouse model for asthma to determine the effect of PI3K inhibitors and PTEN on allergen-induced bronchial inflammation and airway hyperresponsiveness. PI3K activity increased significantly after allergen challenge. PTEN protein expression and PTEN activity were decreased in OVA-induced asthma. Immunoreactive PTEN localized in epithelial layers around the bronchioles in control mice. However, this immunoreactive PTEN dramatically disappeared in allergen-induced asthmatic lungs. The increased IL-4, IL-5, and eosinophil cationic protein levels in bronchoalveolar lavage fluids after OVA inhalation were significantly reduced by the intratracheal administration of PI3K inhibitors or adenoviruses carrying PTEN cDNA (AdPTEN). Intratracheal administration of PI3K inhibitors or AdPTEN remarkably reduced bronchial inflammation and airway hyperresponsiveness. These findings indicate that PTEN may play a pivotal role in the pathogenesis of the asthma phenotype.

Morphological assessment of the development of multinucleated giant cells in glioma by using mitosis-specific phosphorylated antibodies

OBJECT

The nature and origin of multinucleated giant cells in glioma have not been made clear. To investigate the phosphorylation of intermediate filaments, the authors studied multinucleated giant cells in vitro and in vivo by using mitosis-specific phosphorylated antibodies.

METHODS

Cultured human glioma cells were immunostained with monoclonal antibodies (mAbs) 4A4, KT13, and TM71, which recognized the phosphorylation of vimentin at Ser55, glial fibrillary acidic protein at Serl3, and vimentin at Ser71, respectively. Subsequently, the nature of multinucleated giant cells was investigated using laser scanning confocal microscopy. In addition, paraffin-embedded tissue sections obtained in three patients with giant cell glioblastoma were also investigated. Multinucleated giant cells were immunoreacted with the mAb 4A4 and not with KT13 and TM71 in vitro and in vivo. In addition, the authors obtained these results in multinucleated giant cells under natural conditions, without drug treatments.

CONCLUSIONS

Findings in this investigation indicated that multinucleated giant cells are those remaining in mitosis between metaphase and telophase, undergoing neither fusion nor degeneration.

Macrophage-mediated innate host defense against protozoan parasites

Macrophages are immune cells that play a pivotal role in the detection and elimination of pathogenic microorganisms. Macrophages possess a variety of surface receptors devoted to the recognition of non-self by discriminating between host and pathogen-derived structures. Recognition of foreign microorganisms by the macrophage ultimately results in phagocytosis and the eventual destruction of microorganisms by lysosomal enzymes, toxic reactive oxygen and nitrogen intermediates, and/or nutrient deprivational mechanisms. However, protozoan parasites such as Toxoplasma gondii, Trypanosoma cruzi, and Leishmania spp., parasitize macrophages, utilizing them as a host cell for their growth, replication, and/or maintenance of their life cycles. The protozoan parasites of the genus Leishmania are unique in that their intracellular replication in the host is predominantly restricted to a single cell type, the macrophage. This review focuses on the cellular processes involved in macrophage-mediated host defense against protozoan parasites, from the initial host-parasite interactions that mediate recognition to the mechanisms employed by macrophages to destroy and eliminate the pathogen. As an example model system of experimental study, we describe in more more detail the cellular interactions between macrophages and the obligate intracellular parasite of mammalian macrophages, Leishmania spp.

Calcineurin phosphatase activity and immunosuppression. A review on the role of calcineurin phosphatase activity and the immunosuppressive effect of cyclosporin A and tacrolimus

The mode of immunosuppressive action of tacrolimus (FK506) and cyclosporin A has been elucidated. Both drugs bind to proteins in the cytoplasm to form complexes, which in turn inhibit the phosphatase activity of calcineurin, an important limiting step in the activation of T cells. The association between drug uptake (pharmacokinetics) and enzyme inhibition (pharmacodynamics) is under current investigation. Great variations in the correlation between blood drug levels and enzyme inhibition could indicate that monitoring calcineurin phosphatase activity for treatment might be superior to monitoring blood drug levels.

Modulation of CD40L antigen expression in Jurkat cells: involvement of protein kinase C activity

The CD40L expressed on activated CD4+ T cells delivers contact-dependent proliferative and anti-apoptotic signals to B lymphocytes. Little is known about molecular mechanisms of constitutive expression of CD40L on some non-Hodgkin's lymphomas, especially about involvement of two signal pathways regulating its expression in normal cells; one involving calcineurin, and the other protein kinase C. We analyzed by flow cytometry the effects of 6-hour stimulation of both pathways (stimuli: PMA and ionomycin) and their inhibitors: cyclosporin A and chelerythrine, on CD40L expression. Two Jurkat clones differing in CD40L surface expression: clone 217.6 (CD40L-) and 217.7 (CD40L+) were studied. Our experiments showed that high level of CD40L expression on the surface of 217.7 cells was reduced after stimulation with PMA. The same effect was observed for combination of PMA and chelerythrine or for PKC inhibitor alone. In 217.6 cells, only chelerythrine used alone induced low level of CD40L expression, while PMA and ionomycin were without effect. These results suggest that CD40L surface expression is mainly dependent on protein kinase C activity. By using PepTag Assay we have confirmed that in both Jurkat clones PKC activity is higher than in normal blood lymphocytes.

Loss of a single allele of SHIP exacerbates the immunopathology of Pten heterozygous mice

Phosphatidylinositol 3-kinase (PI3K) has emerged as a critical component of multiple immune system intracellular signalling pathways. The levels and relative ratios of PI3K products, phosphatidylinositol (3,4) bisphosphate (PI(3,4)P(2)) and phosphatidylinositol (3,4,5) trisphosphate (PIP(3)), are regulated by inositol phosphatases such as Pten and SHIP. Interestingly, mice heterozygous for Pten, a 3'-inositol phosphatase, develop a progressive lymphoproliferative syndrome with autoimmune features. Given the importance of PIP(3) species in regulating immune responses, we hypothesized that heterozygosity for the 5'-inositol phosphatase SHIP might exacerbate the autoimmune phenotype of Pten(+/-) mice. In keeping with this, mice heterozygous for both Pten and SHIP developed lymphoproliferation, hypergammaglobulinaemia, autoantibody titres and renal pathology that were more severe than that of Pten(+/-) mice. These results suggest that the relative levels of phosphatidylinositol phosphatases are likely critical to immune system homeostasis and they also highlight the potential for gene dosage effects in regulating susceptibility and/or severity of autoimmunity.

Differentiation of the human monocyte cell line, U937, with dibutyryl cyclicAMP induces the expression of the inhibitory Fc receptor, FcgammaRIIb

FC receptor for IgG receptor (Fcgamma) mediated activation of macrophages is essential for the clearance of immune complexes and control of inflammation. However, activated macrophages play an integral role in tissue destruction associated with autoimmune and inflammatory disease processes. Understanding the mechanisms which balance activating and inhibitory signals generated by immune complexes are therefore of critical importance to human disease. Here, we demonstrate that differentiation of the human monocytic U937 cell line to a macrophage phenotype with dibutyryl cyclicAMP induces both mRNA and protein expression of the inhibitory IgG receptor, FcgammaRIIb1. We further demonstrate that, following receptor aggregation, FcgammaRII transiently recruits the 5'-inositol phosphatase, SHIP. These data define a role for FcgammaRIIb in the modulation of immune complex mediated macrophage activation in a human model system.

Excessive expression of synaptojanin in brains with Down syndrome

We investigated the expression of synaptojanin, which has been mapped on 21q22.2 on human chromosome, in the cerebral cortex of patients with Down syndrome (DS), using immunohistochemistry and immunoblotting. Synaptojanin expression was observed in Cajal-Retzius cells, cortical plate neurons, subplate neurons, intermediate neurons, germinal matrix cells and the ventricular neuroepithelium of the fetal cerebrum in both controls and DS. After birth, synaptojanin immunoreactivity was mainly observed in cytoplasm of cortical neurons and neurophils. These expressions of synaptojanin suggest a broader role in not only synaptic vesicle recycling, but also the regulation of neuronal migration and synaptogenesis in the fetal period. In comparison with controls, DS brains clearly showed higher immunoreactivity of synaptojanin in every structure, and most of the large neurons showed immunoreactivity. Western blotting with synaptojanin confirmed the increased expression in DS brains. Although the reason for excessive expression of synaptojanin in DS brains is obscured, one possibility can be explained on the basis of a gene dosage effect. As another possibility, on the assumption that synaptojanin modulates synaptic transmission and plays roles in clathrin-mediated synaptic vesicle endocytosis and signaling, the excessive expression of synaptojanin may be involved in compensatory mechanisms occurring in developing DS brains, such as neuronal loss, atrophic basilar dendrites, decreased spines and abnormal synaptic density and length.

Regulation of the immune response by SHIP

Multiple lines of experimental data indicate that SHIP1 is an important negative regulator of the immune system. SHIP1 has been demonstrated to control survival and proliferation, as well as differentiation. In the cases of some inhibitory receptors, such as Fc gamma RIIB1, the molecular mechanisms of control by SHIP1 are established. For other receptors, particularly activating receptors where SHIP1 appears to set activation thresholds, the mechanisms remain to be discovered. Further study on SHIP and other SHIP family members could be critical for our understanding the negative regulation in multiple hematopoietic lineages and the immune system as a whole.

T cell-specific loss of Pten leads to defects in central and peripheral tolerance

PTEN, a tumor suppressor gene, is essential for embryogenesis. We used the Cre-loxP system to generate a T cell-specific deletion of the Pten gene (Pten(flox/-) mice). All Pten(flox/-) mice develop CD4+ T cell lymphomas by 17 weeks. Pten(flox/-) mice show increased thymic cellularity due in part to a defect in thymic negative selection. Pten(flox/-) mice exhibit elevated levels of B cells and CD4+ T cells in the periphery, spontaneous activation of CD4+ T cells, autoantibody production, and hypergammaglobulinemia. Pten(flox/-) T cells hyperproliferate, are autoreactive, secrete increased levels of Th1/Th2 cytokines, resist apoptosis, and show increased phosphorylation of PKB/Akt and ERK. Peripheral tolerance to SEB is also impaired in Pten(flox/-) mice. PTEN is thus an important regulator of T cell homeostasis and self-tolerance.

A regulatory role for Src homology 2 domain-containing inositol 5'-phosphatase (SHIP) in phagocytosis mediated by Fc gamma receptors and complement receptor 3 (alpha(M)beta(2); CD11b/CD18)

The Src homology 2 domain-containing inositol 5'-phosphatase (SHIP) is recruited to immunoreceptor tyrosine-based inhibition motif (ITIM)-containing proteins, thereby suppressing phosphatidylinositol 3-kinase (PI 3-kinase)-dependent pathways. The role of SHIP in phagocytosis, a PI 3-kinase-dependent pathway, is unknown. Overexpression of SHIP in macrophages led to an inhibition of phagocytosis mediated by receptors for the Fc portion of IgG (Fc gamma Rs). In contrast, macrophages expressing catalytically inactive SHIP or lacking SHIP expression demonstrated enhanced phagocytosis. To determine whether SHIP regulates phagocytosis mediated by receptors that are not known to recruit ITIMs, we determined the effect of SHIP expression on complement receptor 3 (CR3; CD11b/CD18; alpha(M)beta(2))-dependent phagocytosis. Macrophages overexpressing SHIP demonstrated impaired CR3-mediated phagocytosis, whereas macrophages expressing catalytically inactive SHIP demonstrated enhanced phagocytosis. CR3-mediated phagocytosis in macrophages derived from SHIP(-/-) mice was up to 2.5 times as efficient as that observed in macrophages derived from littermate controls. SHIP was localized to Fc gamma R- and CR3-containing phagocytic cups and was recruited to the cytoskeleton upon clustering of CR3. In a transfected COS cell model of activation-independent CR3-mediated phagocytosis, catalytically active but not inactive SHIP also inhibited phagocytosis. We conclude that PI 3-kinase(s) and SHIP regulate multiple forms of phagocytosis and that endogenous SHIP plays a role in modulating beta(2) integrin outside-in signaling.

SHIP inhibits Akt activation in B cells through regulation of Akt membrane localization

Activation of the serine/threonine kinase Akt and the regulation of its activation are recognized as critical in controlling proliferative/survival signals via many hematopoietic receptors. In B lymphocytes, the B-cell receptor (BCR)-mediated activation of Akt is attenuated by co-cross-linking of BCR with the inhibitory receptor Fc gamma RIIB1, and the binding of the SH2 domain-containing inositol phosphatase, SHIP, to Fc gamma RIIB1. Because SHIP dephosphorylates phosphatidylinositol 3,4,5-trisphosphate (PIP3) and activation of Akt requires PIP3, the destruction of this phospholipid has been proposed as the mechanism for Akt inhibition. However, upstream kinases that activate Akt, such as PDK1, also require PIP3 for activation. In this report, we addressed whether SHIP inhibits Akt directly at the level of Akt recruitment to the membrane, indirectly through PDK recruitment/phosphorylation of Akt, or both. We generated stable B-cell lines expressing a regulatable, but constitutively membrane-bound Akt that still required PDK-dependent phosphorylation for activation. Several lines of evidence suggested that activation of this membrane-targeted Akt is not inhibited by Fc gamma RIIB1/SHIP and that PDK is not a target for SHIP-mediated inhibition. These data demonstrate that SHIP inhibits Akt primarily through regulation of Akt membrane localization. We also observed during these studies that Fc gamma RIIB1/SHIP does not inhibit p70(S6k) activation, even though several other PIP3-dependent events were down-regulated. Because the enhanced activation of Akt in the absence of SHIP correlates with hyperproliferation in the myeloid lineage, our data have implications for SHIP and Akt-dependent regulation of proliferation in the hematopoietic lineage. (Blood. 2000;96:1449-1456)

Lipid phosphatases in the immune system

In the last 10 years we have come to appreciate the central role that phosphatidylinositol (PI)-3,4,5-P(3)plays in regulating a vast array of biological responses to extracellular signals. The level of this phospholipid is low in resting cells but increases rapidly in response to growth factor/cytokine-stimulated plasma membrane recruitment and activation of PI-3-kinase. Within the last 3 years three enzymes, SHIP, SHIP2 and PTEN, that play key roles in regulating the level of PI-3,4,5-P(3)have been cloned. In this review I have attempted to summarize our current knowledge regarding these three intriguing phosphatases.

Effects of two novel cationic staphylococcal proteins (NP-tase and p70)and enterotoxin B on IgE synthesis and interleukin-4 and interferon-gamma production in patients with atopic dermatitis

We have characterized the cell-mediated and humoral immune response of patients with atopic dermatitis (AD) and healthy controls in response to two novel staphylococcal antigens (NP-tase, p70) and the superantigen staphylococcal enterotoxin B (SEB). The parameters studied were IgE, interleukin (IL)-4 and interferon (IFN)-gamma synthesis by peripheral blood mononuclear cells (PBMC) after stimulation with NP-tase, p70 and SEB in vitro. Both antigens, as well as SEB, induced IL-4 and IFN-gamma secretion in patients and controls. However, patients with AD showed a significantly diminished IFN-gamma production in response to NP-tase or SEB. Furthermore, we demonstrated a good correlation between antigen-stimulated IgE production and the IL-4/IFN-gamma ratio in vitro. A distinct subgroup of PBMC showed impaired IFN-gamma synthesis and enhanced IL-4 secretion after incubation with p70 or NP-tase. These data support evidence that a subgroup of patients with AD, synthesizing low levels of IFN-gamma after stimulation with staphylococcal antigens, may have impaired abilities to clear Staphylococcus aureus colonization. Persistent staphylococcal antigens could then be responsible for inflammatory and allergic skin reactions in patients with AD. We therefore conclude that, besides superantigens, staphylococcal antigens may also play a part in the pathogenesis of AD.

A dual role for Src homology 2 domain-containing inositol-5-phosphatase (SHIP) in immunity: aberrant development and enhanced function of b lymphocytes in ship -/- mice

In this report, we demonstrate that the Src homology 2 domain-containing inositol-5-phosphatase (SHIP) plays a critical role in regulating both B cell development and responsiveness to antigen stimulation. SHIP(-/-) mice exhibit a transplantable alteration in B lymphoid development that results in reduced numbers of precursor B (fraction C) and immature B cells in the bone marrow. In vitro, purified SHIP(-/)- B cells exhibit enhanced proliferation in response to B cell receptor stimulation in both the presence and absence of Fcgamma receptor IIB coligation. This enhancement is associated with increased phosphorylation of both mitogen-activated protein kinase and Akt, as well as with increased survival and cell cycling. SHIP(-/)- mice manifest elevated serum immunoglobulin (Ig) levels and an exaggerated IgG response to the T cell-independent type 2 antigen trinitrophenyl Ficoll. However, only altered B cell development was apparent upon transplantation into nonobese diabetic-severe combined immunodeficient (NOD/SCID) mice. The in vitro hyperresponsiveness, together with the in vivo findings, suggests that SHIP regulates B lymphoid development and antigen responsiveness by both intrinsic and extrinsic mechanisms.

Effects of Src homology domain 2 (SH2)-containing inositol phosphatase (SHIP), SH2-containing phosphotyrosine phosphatase (SHP)-1, and SHP-2 SH2 decoy proteins on Fc gamma RIIB1-effector interactions and inhibitory functions

Coaggregation of Fc gamma RIIB1 with B cell Ag receptors (BCR) leads to inhibition of BCR-mediated signaling via recruitment of Src homology domain 2 (SH2)-containing phosphatases. In vitro peptide binding experiments using phosphotyrosine-containing sequences derived from the immunoreceptor tyrosine-based inhibitory motif (ITIM) known to mediate Fc gamma RIIB1 effects suggest that the receptor uses SH2-containing inositol phosphatase (SHIP) and SH2-containing phosphotyrosine phosphatase (SHP)-1, as well as SHP-2 as effectors. In contrast, coimmunoprecipitation studies of receptor-effector associations suggest that the predominant Fc gamma RIIB1 effector protein is SHIP. However, biologically significant interactions may be lost in such studies if reactants' dissociation rates (Kd) are high. Thus, it is unclear to what extent these assays reflect the relative recruitment of SHIP, SHP-1, and SHP-2 to the receptor in vivo. As an alternative approach to this question, we have studied the effects of ectopically expressed SHIP, SHP-1, or SHP-2 SH2-containing decoy proteins on Fc gamma RIIB1 signaling. Results demonstrate the SHIP is the predominant intracellular ligand for the phosphorylated Fc gamma RIIB1 ITIM, although the SHP-2 decoy exhibits some ability to bind Fc gamma RIIB1 and block Fc receptor function. The SHIP SH2, while not affecting Fc gamma RIIB1 tyrosyl phosphorylation, blocks receptor-mediated recruitment of SHIP, SHIP phosphorylation, recruitment of p52 Shc, phosphatidylinositol 3,4,5-trisphosphate hydrolysis, inhibition of mitogen-activated protein kinase activation, and, albeit more modestly, Fc gamma RIIB1 inhibition of Ca2+ mobilization. Taken together, results implicate ITIM interactions with SHIP as a major mechanism of Fc gamma RIIB1-mediated inhibitory signaling.

Immunohistochemical evidence of loss of PTEN expression in primary ductal adenocarcinomas of the breast

Germline mutations in PTEN, encoding a dual-specificity phosphatase on 10q23.3, cause Cowden syndrome (CS), which is characterized by a high risk of breast and thyroid cancers. Loss of heterozygosity of 10q22-24 markers and somatic PTEN mutations have been found to a greater or lesser extent in a variety of sporadic component and noncomponent cancers of CS. Among several series of sporadic breast carcinomas, the frequency of loss of flanking markers around PTEN is approximately 30 to 40%, and the somatic intragenic PTEN mutation frequency is <5%. In this study, we analyzed PTEN expression in 33 sporadic primary breast carcinoma samples using immunohistochemistry and correlated this to structural studies at the molecular level. Normal mammary tissue had a distinctive pattern of expression: myoepithelial cells uniformly showed strong PTEN expression. The PTEN protein level in mammary epithelial cells was variable. Ductal hyperplasia with and without atypia exhibited higher PTEN protein levels than normal mammary epithelial cells. Among the 33 carcinoma samples, 5 (15%) were immunohistochemically PTEN-negative; 6 (18%) had reduced staining, and the rest were PTEN-positive. In the PTEN-positive tumors as well as in normal epithelium, the protein was localized in the cytoplasm and in the nucleus (or nuclear membrane). Among the immunostain negative group, all had hemizygous PTEN deletion but no structural alteration of the remaining allele. Thus, in these cases, an epigenetic phenomenon such as hypermethylation, -ecreased protein synthesis or increased protein degradation may be involved. In the cases with reduced staining, 5 of 6 had hemizygous PTEN deletion and 1 did not have any structural abnormality. Finally, clinicopathological features were analyzed against PTEN protein expression. Three of the 5 PTEN immunostain-negative carcinomas were also both estrogen and progesterone receptor-negative, whereas only 5 of 22 of the PTEN-positive group were double receptor-negative. The significance of this last observation requires further study.