Search

Objective: Novel autoantibody specificities including anti‐CCAR1 were recently discovered in adult patients with anti‐transcriptional intermediary factor (TIF1)–positive dermatomyositis (DM) and were associated with attenuated cancer emergence. The aims of the present study were to examine whether these autoantibodies occur in patients with juvenile‐onset DM (JDM) and to determine their associated features. Methods: Sera from 150 patients with anti‐TIF1γ autoantibody‐positive JDM in a cross‐sectional cohort and 90 juvenile healthy controls were assayed for anti‐CCAR1, anti‐C1Z1, anti‐IMMT, anti‐TBL1XR1, and anti‐Sp4 autoantibodies. Demographics, myositis autoantibodies, clinical features, medications, outcomes, and HLA‐DRB1 and HLA‐DQA1 alleles were compared between those with and without these autoantibodies. Results: Any one of the anti‐TIF1γ‐associated autoantibodies was present in 44 patients (29%) overall, including 25 (17%) with anti‐Sp4, 22 (15%) with anti‐TBL1XR1, 14 (9%) with anti‐CCAR1, 2 (1%) with anti‐C1Z1, and 2 (1%) with anti‐IMMT autoantibodies. These anti‐TIF1γ‐associated autoantibodies frequently co‐occurred. Patients with any of the anti‐TIF1γ‐associated autoantibodies had less frequent falling (34% [15] vs. 53% [56], P = 0.032) and lower peak muscle enzymes. None of the patients had cancer. Among White patients, HLA‐DRB1*03 was protective against an anti‐TIF1γ‐associated autoantibody (odds ratio 0.20, 95% confidence interval 0.07–0.52). Conclusion: Autoantibodies associated with anti‐TIF1γ were found in isolation and in combination among a subset of patients with JDM. Patients with these autoantibodies had less severe muscle disease and were not enriched for HLA‐DRB1*03. Additional autoantibodies among patients with positive anti‐TIF1γ with JDM likely contribute to the heterogeneity of the anti‐TIF1γ serologic subgroup. [ABSTRACT FROM AUTHOR]

Lipid rafts are important signaling platforms in T cells. Little is known about their properties in human CD[8.sup.+] T cells. We studied polarization of lipid rafts by digital immunofluorescence microscopy in primary human T cells, using beads coated with anti-CD3 and anti-CD28 mAbs (CD3/28 beads). Unlike CD[4.sup.+] T cells, CD[8.sup.+] T cells did not polarize lipid rafts when stimulated with CD3/28 beads, when the anti-CD28 antibody was substituted with B7.21g, or if an anti-CD8 antibody was added to the CD3/28 beads. This phenomenon was also observed in human antigen-specific CD[8.sup.+] T cells. On stimulation with CD3/28 beads, the T cell antigen receptor clustered at the cell/bead contact area in both CD[4.sup.+] and CD[8.sup.+] T cells. Examination of lipid rafts isolated by sucrose density gradient centrifugation revealed the constitutive expression of [p.sup.56]Lck in the raft fractions of unstimulated CD[8.sup.+] T cells, whereas [p.sup.56]Lck was recruited to the raft fraction of CD[4.sup.+] T cells only after stimulation with CD3/28 beads. Stimulation with CD3/28 beads induced marked calcium flux, recruitment of PKC-[theta] and F-actin to the cell/bead contact site, and similar proliferation patterns in CD[4.sup.+] and CD[8.sup.+] T cells. Thus, polarization of lipid rafts is not essential for early signal transduction events or proliferation of human CD[8.sup.+] lymphocytes. It is possible that the lower stringency of CD[8.sup.+] T cell activation obviates a requirement for raft polarization.

Abstract Background Central nervous system involvement occurs in as many as twenty percent of Takayasu arteritis cases. When central nervous system disease is present, it typically manifests as cerebral ischemia or stroke. There are rare reports of intracranial aneurysms in adults with Takayasu arteritis, but none in children. Case presentation We describe a case of Takayasu arteritis in an 18 month old girl who presented with a ruptured cerebral aneurysm. Full body magnetic resonance angiography revealed bilateral iliac, pelvic and intragluteal aneurysms, irregular terminal aorta, and stenotic renal arteries. Iliac vessel biopsy showed a lymphocytic infiltrate and giant cells localized to the internal elastica. Conclusion This case highlights cerebral aneurysm as a highly unusual initial manifestation of Takayasu arteritis and demonstrates the challenges of diagnosis, treatment, and assessment of response to therapy in TA in children.

Emerging research suggests that chimeric antigen receptor T cell therapy could be an effective treatment for a range of difficult-to-treat autoimmune diseases, and sophisticated approaches are in tests, yet initial reports also highlight several questions that remain to be answered. [ABSTRACT FROM AUTHOR]

Background: Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic disease among children, the etiology of which involves a strong genetic component, but much of the underlying genetic determinants still remain unknown. Our aim was to identify novel genetic variants that predispose to JIA. Methods: We performed a genome-wide association study (GWAS) and replication in a total of 1166 JIA cases and 9500 unrelated controls of European ancestry. Correlation of SNP genotype and gene expression was investigated. Then we conducted targeted resequencing of a candidate locus, among a subset of 480 cases and 480 controls. SUM test was performed to evaluate the association of the identified rare functional variants. Results: The CXCR4 locus on 2q22.1 was found to be significantly associated with JIA, peaking at SNP rs953387. However, this result is subjected to subpopulation stratification within the subjects of European ancestry. After adjusting for principal components, nominal significant association remained (p < 10-4). Because of its interesting known function in immune regulation, we carried out further analyses to assess its relationship with JIA. Expression of CXCR4 was correlated with CXCR4 rs953387 genotypes in lymphoblastoid cell lines (p = 0.014) and T-cells (p = 0.0054). In addition, rare non-synonymous and stop-gain sequence variants in CXCR4, putatively damaging for CXCR4 function, were significantly enriched in JIA cases (p = 0.015). Conclusion: Our results suggest the association of CXCR4 variants with JIA, implicating that this gene may be involved in the pathogenesis of autoimmune disease. However, because this locus is subjected to population stratification within the subjects of European ancestry, additional replication is still necessary for this locus to be considered a true risk locus for JIA. This cell-surface chemokine receptor has already been targeted in other diseases and may serve as a tractable therapeutic target for a specific subset of pediatric arthritis patients with additional replication and functional validation of the locus. [ABSTRACT FROM AUTHOR]

REDD1 is a highly conserved stress response protein that is upregulated following many types of cellular stress, including hypoxia, DNA damage, energy stress, ER stress, and nutrient deprivation. Recently, REDD1 was shown to be involved in dexamethasone induced autophagy in murine thymocytes. However, we know little of REDD1’s function in mature T cells. Here we show for the first time that REDD1 is upregulated following T cell stimulation with PHA or CD3/CD28 beads. REDD1 knockout T cells exhibit a defect in proliferation and cell survival, although markers of activation appear normal. These findings demonstrate a previously unappreciated role for REDD1 in T cell function. [ABSTRACT FROM AUTHOR]

Antigen recognition by T cells relies on the interaction between T cell receptor (TCR) and peptide-major histocompatibility complex (pMHC) at the interface between the T cell and the antigen presenting cell (APC). The pMHC-TCR interaction is two-dimensional (2D), in that both the ligand and receptor are membrane-anchored and their movement is limited to 2D diffusion. The 2D nature of the interaction is critical for the ability of pMHC ligands to trigger TCR. The exact properties of the 2D pMHC-TCR interaction that enable TCR triggering, however, are not fully understood. Here, we altered the 2D pMHC-TCR interaction by tethering pMHC ligands to a rigid plastic surface with flexible poly(ethylene glycol) (PEG) polymers of different lengths, thereby gradually increasing the ligands’ range of motion in the third dimension. We found that pMHC ligands tethered by PEG linkers with long contour length were capable of activating T cells. Shorter PEG linkers, however, triggered TCR more efficiently. Molecular dynamics simulation suggested that shorter PEGs exhibit faster TCR binding on-rates and off-rates. Our findings indicate that TCR signaling can be triggered by surface-tethered pMHC ligands within a defined 3D range of motion, and that fast binding rates lead to higher TCR triggering efficiency. These observations are consistent with a model of TCR triggering that incorporates the dynamic interaction between T cell and antigen-presenting cell. [ABSTRACT FROM AUTHOR]

T cell activation is the result of direct cell-cell contact between T cells and antigen presenting cells (APCs), and of interactions between membrane-bound ligands and receptors at the contact interface, the 'immunological synapse.' Model APCs based upon supported fluid lipid bilayers have been used to dissect these complex molecular interactions and to facilitate real-time microscopic observations. Nearly all studies have used liposome fusion-based methods to make supported bilayers, and the biophysical properties of these membranes were not characterized in detail. Here, using both Langmuir-Blodgett and liposome fusion techniques, we explored five different methods of lipid bilayer preparation on glass, mica, or dextran cushion substrates and characterized the stability, homogeneity, and fluidity of the bilayers with fluorescence microscopy and fluorescence recovery after photobleaching (FRAP). Most combinations of techniques and substrates led to unsatisfactory results, notably, a lack of homogeneity for liposome fusion on glass, low stability of bilayers on mica, and loss of fluidity of dextran-cushioned bilayers in solutions containing protein. To overcome these deficits, we developed a technique that combines liposome fusion on glass and thermally enhanced bilayer expansion. The newly expanded pristine bilayer showed high degrees of stability, homogeneity, and fluidity. MHC and ICAM-1 molecules anchored on the bilayer diffused freely and stimulated T cell calcium flux and adhesion, respectively. Microsc. Res. Tech., 2011. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Objective To describe an enthesitis-related arthritis (ERA) inception cohort and determine which entheses and joints are most commonly affected. Methods We reviewed a retrospective inception cohort study of children with ERA who were diagnosed and treated at The Children's Hospital of Philadelphia between November 2007 and December 2009. Results During the study period, there were 32 newly diagnosed ERA patients. Fifty-nine percent were male, and the median age at the date of initial evaluation was 12.5 years (interquartile range [IQR] 10.2-14.3 years). The median number of tender entheses at presentation was 2 (IQR 0-5), and 21 subjects (66%) had at least 1 tender enthesis. The most prevalent tender entheses were the patellar ligament insertion at the inferior pole of the patella, the plantar fascial insertion at the calcaneus, the Achilles tendon insertion at the calcaneus, and the plantar fascial insertion at the metatarsal heads. Enthesitis was most often symmetric. The median number of active joints was 2 (IQR 0-4). The most commonly affected joints were the sacroiliacs, knees, and ankles. Sacroiliitis, which was defined clinically, was most often symmetric, while peripheral arthritis was most frequently asymmetric. The odds of having active enthesitis at 6 months increased significantly with each additional tender enthesis at the initial evaluation. Conclusion Among pediatric patients with ERA, lower extremity enthesitis is prevalent at the time of diagnosis and is likely to persist 6 months later. Future studies should address standardization of the enthesitis examination, the pattern of enthesitis over time, enthesitis response to therapy, and the impact of enthesitis on quality of life. [ABSTRACT FROM AUTHOR]

Prior work has implicated viral protein R (Vpr) in the arrest of human immunodeficiency virus type 1 (HIV-1)–infected cells in the G2 phase of the cell cycle, associated with increased viral replication and host cell apoptosis. We and others have recently shown that virion infectivity factor (Vif ) also plays a role in the G2 arrest of HIV-1–infected cells. Here, we demonstrate that, paradoxically, at early time points postinfection, Vif expression blocks Vpr-mediated G2 arrest, while deletion of Vif from the HIV-1 genome leads to a marked increase in G2 arrest of infected CD4 T-cells. Consistent with this increased G2 arrest, T-cells infected with Vif-deleted HIV-1 express higher levels of Vpr protein than cells infected with wild-type virus. Further, expression of exogenous Vif inhibits the expression of Vpr, associated with a decrease in G2 arrest of both infected and transfected cells. Treatment with the proteasome inhibitor MG132 increases Vpr protein expression and G2 arrest in wild-type, but not Vif-deleted, NL4-3–infected cells, and in cells cotransfected with Vif and Vpr. In addition, Vpr coimmunoprecipitates with Vif in cotransfected cells in the presence of MG132. This suggests that inhibition of Vpr by Vif is mediated at least in part by proteasomal degradation, similar to Vif-induced degradation of APOBEC3G. Together, these data show that Vif mediates the degradation of Vpr and modulates Vpr-induced G2 arrest in HIV-1–infected T-cells. [ABSTRACT FROM AUTHOR]

Through T cell receptors (TCRs), T cells can detect and respond to very small numbers of foreign peptides among a huge number of self-peptides presented by major histocompatibility complexes (pMHCs) on the surface of antigen-presenting cells (APCs). How T cells achieve such remarkable sensitivity and specificity through pMHC-TCR binding is an intensively pursued issue in immunology today; the key question is how pMHC-TCR binding initiates, or triggers, a signal from TCRs. Multiple competing models have been proposed, none of which fully explains the sensitivity and specificity of TCR triggering. What has been omitted from existing theories is that the pMHC-TCR interaction at the T cell/APC interface must be under constant mechanical stress, due to the dynamic nature of cell-cell interaction. Taking this condition into consideration, we propose the receptor deformation model of TCR triggering. In this model, TCR signaling is initiated by conformational changes of the TCR/CD3 complex, induced by a pulling force originating from the cytoskeleton and transmitted through pMHC-TCR binding interactions with enough strength to resist rupture. By introducing mechanical force into a model of T cell signal initiation, the receptor deformation model provides potential mechanistic solutions to the sensitivity and specificity of TCR triggering. [ABSTRACT FROM AUTHOR]

Why is it that T cells are blind to antigens in solution but highly sensitive to antigens anchored on a surface? The authors show that this is not due to antigen clustering, but could involve mechanical forces associated with cell locomotion. [ABSTRACT FROM AUTHOR]

The article explores the mechanical force in T cell receptor (TCR). It mentions that TCR translates mechanical forces into biochemical signals. It notes that mechanical forces are applied in the interaction between the T cell and antigen presenting cell (APC). It emphasizes that the mechanical force also serves as an important part in the cell physiology and key to the mechanism of TCR triggering.

We describe a case of pediatric Sjögren's syndrome with progressive neurologic involvement. At age 4 years, she had been diagnosed with Melkersson-Rosenthal syndrome. After being stable with facial diplegia trod swelling for 5 years, she acutely presented with diplopia, vertigo, and ataxia. Cranial magnetic resonance imaging (MRI) showed a left dorsal midbrain lesion. Serologic and histopathologic findings confirmed primary Sjögren's syndrome. She responded well to intravenous methylprednisolone, with subsequent clinical improvement and MRI resolution. This report reviews the pediatric literature and underscores the importance of considering Sjögren's syndrome in a child with unexplained facial weakness and in the differential diagnosis of pediatric stroke. (J Child Neurol 2001;16:683–685). [ABSTRACT FROM AUTHOR]

Gene transfer into primary human CD4 T lymphocytes is a critical tool in studying the mechanism of T cell-dependent immune responses and human immunodeficiency virus-1 (HIV-1) infection. Nucleofection® is an electroporation technique that allows efficient gene transfer into primary human CD4 T cells that are notoriously resistant to traditional electroporation. Despite its popularity in immunological research, careful characterization of its impact on the physiology of CD4 T cells has not been documented. Herein, using freshly-isolated primary human CD4 T cells, we examine the effects of Nucleofection® on CD4 T cell morphology, intracellular calcium levels, cell surface activation markers, and transcriptional activity. We find that immediately after Nucleofection®, CD4 T cells undergo dramatic morphological changes characterized by wrinkled and dilated plasma membranes before recovering 1h later. The intracellular calcium level also increases after Nucleofection®, peaking after 1h before recovering 8h post transfection. Moreover, Nucleofection® leads to increased expression of T cell activation markers, CD154 and CD69, for more than 24h, and enhances the activation effects of phytohemagglutinin (PHA) stimulation. In addition, transcriptional activity is increased in the first 24h after Nucleofection®, even in the absence of exogenous stimuli. Therefore, Nucleofection® significantly alters the activation state of primary human CD4 T cells. The effect of transferred gene products on CD4 T cell function by Nucleofection® should be assessed after sufficient resting time post transfection or analyzed in light of the activation caveats mentioned above. [ABSTRACT FROM AUTHOR]

Abstract: Although HIV-1 (HIV) replicates poorly in non-dividing CD4 lymphocytes, resting T cells contribute to the latent reservoir. The γc-related cytokines reverse this block to HIV infection; however, the molecular mechanisms controlling this process are not understood. We asked whether the γc-cytokine regulated transcription factor, signal transducer and activator of transcription 5 (STAT5), activates HIV transcription. We identified three regions in the long terminal repeat (LTR) as close matches to the STAT5 consensus-binding site and show that STAT5 binds the LTR during HIV infection. Expression of Janus kinase 3 (JAK3) or STAT5 in primary human CD4 T cells activated LTR transcription, while transactivation-incompetent dominant-negative STAT5 inhibited JAK3-induced LTR activity and infection of activated HIV-producing CD4 T-cells. In addition, overexpression of STAT5 increased virus production in unstimulated primary T cells – both the number of p24+ cells and their level of p24 production – suggesting that STAT5 promotes a permissive state for HIV infection. These data may have implications for regulation of latency and therapeutic strategies for control of HIV disease. [Copyright &y& Elsevier]