Post-natal paucity of regulatory T cells and control of NK cell activation in experimental biliary atresia

BACKGROUND & AIMS

Although recent studies have identified important roles for T and NK cells in the pathogenesis of biliary atresia (BA), the mechanisms by which susceptibility to bile duct injury is restricted to the neonatal period are unknown.

METHODS

We characterised hepatic regulatory T cells (Tregs) by flow cytometry in two groups of neonatal mice challenged with rhesus rotavirus (RRV) at day 7 (no ductal injury) or day 1 of life (resulting in BA), determined the functional interaction with effector cells in co-culture assays, and examined the effect of adoptive transfer of CD4+ cells on the BA phenotype.

RESULTS

While day 7 RRV infection increased hepatic Tregs (Foxp3+ CD4+ CD25+) by 10-fold within 3 days, no increase in Tregs occurred at this time point following infection on day 1. In vitro, Tregs effectively suppressed NK cell activation by hepatic dendritic cells and decreased the production of pro-inflammatory cytokines, including TNFalpha and IL-15, following RRV infection. In vivo, adoptive transfer of CD4+ cells prior to RRV inoculation led to increased survival, improved weight gain, decreased population of hepatic NK cells, and persistence of donor Tregs in the liver.

CONCLUSIONS

(1) The liver is devoid of Tregs early after perinatal RRV infection; (2) Tregs suppress DC-dependent activation of naive NK cells in vitro, and Treg-containing CD4+ cells inhibit hepatic NK cell expansion in vivo. Thus, the post-natal absence of Tregs may be a key factor that allows hepatic DCs to act unopposed in NK cell activation during the initiation of neonatal bile duct injury.

HIV risk and prevention behaviours, intentions, perceptions and knowledge among youth in Goa, India

In order to examine the association between HIV/AIDS knowledge and perceptions, and risk intentions and behaviours among adolescents in Goa, India, cross-sectional data from 942 youth were collected and assessed. The prevalence rates in the past six months for fighting, smoking, drinking and drug use were 16.5%, 3.8%, 17.8% and 1.1%, respectively; 5.2% acknowledged ever having engaged in sex. Prior risk involvement was significantly correlated with future risk intention (odds ratio [OR]: 9.7-19.7), and those involved in one risk behaviour were more likely to engage in other risk behaviours (OR: 1.3-23.5). The findings suggest the importance of targeted interventions for youth engaging or intending to engage in risk behaviours and universal interventions regarding basic facts and skills for all youth in Goa.

Electrical characterization of self-assembled monolayers of alkyltrichlorosilanes on native oxide of silicon

The octadecyltrichlorosilane (C18), dodecyltrichlorosilane (C12) and octyltrichlorosilane (C8) monolayers have been deposited on the native oxide of silicon by self-assembly technique. The morphology of the monolayers studied by atomic force microscopy revealed an average roughness of approximately 1.0 A. The Fourier Transform Infra Red Spectroscopic measurements revealed the presence of peaks at approximately 2848 and 2915 cm(-1) indicating the formation of densely packed monolayers. The current density versus voltage (J-V) measurements using mercury drop as counter electrode showed tunneling current between 10(-5) to 10(-8) A/cm2 at 1 V indicating the excellent dielectric behaviour of these monolayers. The J-V data were fitted to Simmons theory of tunneling which yielded an effective electron energy barrier height of 1.6 +/- 0.2 eV and the effective mass of electron tunneling through the barrier was found to be 0.3 +/- 0.03 m(e). The tunneling decay factor beta was estimated from the current density values measured as a function of thickness of the monolayer and was found to be 0.28 +/- 0.02 A(-1).

A proinflammatory program of perinatal plasmacytoid dendritic cells activate natural killer (NK) cells to damage the bile duct epithelium in experimental biliary atresia (43.2)

Biliary atresia results from an NK cell-mediated inflammatory injury of the bile duct epithelium with onset in the early postnatal period. Based on key immunoregulatory roles of dendritic cells (DC), we hypothesized that early neonatal DC activation triggers an effector immune response that results in biliary atresia. We tested this hypothesis in a mouse model of rotavirus-induced biliary atresia. Following rotavirus challenge on day 1 of life, viral immunogenic protein NSP3 was detected in hepatic PDCA-1+ plasmacytoid DC (pDC) but not CD11c+ conventional DC (cDC) within 3 days of infection. Hepatic pDC increased 3 fold, while non-pDC (CD11b+CD11c+ cells) decreased 2.5 fold. Rotavirus-naïve perinatal hepatic pDC and cDC spontaneously expressed B7.1/2 (2-3 fold higher than adults), with a much higher increased expression in B7.1/2, IFNγ, and IL-12p40 by pDC after rotavirus challenge. IL-15 was spontaneously expressed by naïve perinatal pDC and increased dramatically after rotavirus infection, but in vitro activation of NK cells required co-culture with both pDC and cDC. Most notably, ablation of pDC decreased the liver population of NK cells and prevented the mucosa injury and obstruction of neonatal bile ducts, leading to improved symptoms and long-term survival. Thus early activation of pDC due upon viral exposure regulates neonatal duct injury and obstruction in biliary atresia.

Dual roles of immunoregulatory cytokine TGF-beta in the pathogenesis of autoimmunity-mediated organ damage

Ample evidence suggests a role of TGF-beta in preventing autoimmunity. Multiorgan inflammatory disease, spontaneous activation of self-reactive T cells, and autoantibody production are hallmarks of autoimmune diseases, such as lupus. These features are reminiscent of the immunopathology manifest in TGF-beta1-deficient mice. In this study, we show that lupus-prone (New Zealand Black and White)F(1) mice have reduced expression of TGF-beta1 in lymphoid tissues, and TGF-beta1 or TGF-beta1-producing T cells suppress autoantibody production. In contrast, the expression of TGF-beta1 protein and mRNA and TGF-beta signaling proteins (TGF-beta receptor type II and phosphorylated SMAD3) increases in the target organs, i.e., kidneys, of these mice as they age and develop progressive organ damage. In fact, the levels of TGF-beta1 in kidney tissue and urine correlate with the extent of chronic lesions that represent local tissue fibrosis. In vivo TGF-beta blockade by treatment of these mice with an anti-TGF-beta Ab selectively inhibits chronic fibrotic lesions without affecting autoantibody production and the inflammatory component of tissue injury. Thus, TGF-beta plays a dual, seemingly paradoxical, role in the development of organ damage in multiorgan autoimmune diseases. According to our working model, reduced TGF-beta in immune cells predisposes to immune dysregulation and autoantibody production, which causes tissue inflammation that triggers the production of anti-inflammatory cytokines such as TGF-beta in target organs to counter inflammation. Enhanced TGF-beta in target organs, in turn, can lead to dysregulated tissue repair, progressive fibrogenesis, and eventual end-organ damage.

A non-invasive, in vivo technique for monitoring vascular status of glioblastoma during angiogenesis

The growth of solid tumors dependent on the process of angiogenesis in which growth factors secreted by tumor and stromal cells promote endothelial cell proliferation, migration, and maturation. This process generates a tumor-specific vascular supply and enables small or dormant tumors to grow rapidly with exponential increases in tumor volume. Determination of tumor oxygenation at the microvascular level will provide important insight into tumor growth, angiogenesis, necrosis, and therapeutic response, and will facilitate to develop protocols for studying tumor behavior. A non-invasive multi-modality approach based on near infrared spectroscopy (NIRS) technique, namely: Steady State Diffuse Optical Spectroscopy (SSDOS) along with Magnetic Resonance Imaging (MRI) is applied for monitoring the concentration of oxyhemoglobin, deoxyhemoglobin and water within tumor region and for studying the vascular status of tumor and the patho-physiological changes that occur during angiogenesis. Since, the growth of solid tumors depends on the formation of new blood vessels, an association between intramural microvessel density (MVD) and tumor oxygenation is also investigated. The relative decrease in oxygenation value with tumor growth indicates that though blood vessels infiltrate and proliferate the tumor region, a hypoxic trend is clearly present.

The Countervailing Actions of Myeloid and Plasmacytoid Dendritic Cells Control Autoimmune Diabetes in the Nonobese Diabetic Mouse

Islet Ag-specific CD4(+) T cells receive antigenic stimulation from MHC class II-expressing APCs. Herein, we delineate the direct in vivo necessity for distinct subsets of macrophages and dendritic cells (DC) in type 1 diabetes mellitus of the NOD mouse by using diphtheria toxin-mediated cell ablation. The ablation of macrophages had no impact on islet Ag presentation or on the induction of insulitis or diabetes in either transfer or spontaneous models. However, the ablation of CD11b(+)CD11c(+) DC led to the loss of T cell activation, insulitis, and diabetes mediated by CD4(+) T cells. When the specific myeloid DC subset was "added-back" to mice lacking total DC, insulitis and diabetes were restored. Interestingly, when NOD mice were allowed to progress to the insulitis phase, the ablation of DC led to accelerated insulitis. This accelerated insulitis was mediated by the loss of plasmacytoid DC (pDC). When pDC were returned to depleted mice, the localized regulation of insulitis was restored. The loss of pDC in the pancreas itself was accompanied by the localized loss of IDO and the acceleration of insulitis. Thus, CD11c(+)CD11b(+) DC and pDC have countervailing actions in NOD diabetes, with myeloid DC providing critical antigenic stimulation to naive CD4(+) T cells and pDC providing regulatory control of CD4(+) T cell function in the target tissue.

Countervailing actions of myeloid and plasmacytoid dendritic cells control autoimmune diabetes (130.36)

Islets specific CD4+ T Cells receive instructional signals from antigen bearing MHC class II-expressing antigen presenting cells (APC), yet the influence of APC on autoimmune diabetes remains elusive. Herein we delineate the direct in vivo necessity for macrophages and dendritic cells in Type 1 Diabetes of the non-obese diabetic (NOD) mouse by using diphtheria toxin-mediated conditional abaltion. We find that specific loss of macrophages had no impact on diabetes or insulitis in both spontaneous and transfer model. Loss of both myeloid (mDC) and lymphoid DC (ly DC) led to protection of NOD mice from diabetes and accompanying loss of T cell activation, while specific loss of plasmacytoid DC (pDC) and Indoleamine 2,3,dioxygenase (IDO) led to breakdown in regulatory control and accelerated insultis. These data imply that autoimmune diabetes is regulated by imbalance of mDC and pDC function in vivo.

CT appearances of hydatid disease at various locations

Hydatid disease has characteristic imaging features on CT, which allow accurate preoperative diagnosis in most cases. However, when it occurs at unusual locations the diagnosis is often difficult, especially as the imaging appearance varies at different sites. In this article we have presented a pictorial review of the CT features of disease due to Echinococcus granulosus at various sites in the human body.

Effect of lectins on the cobalamin-protein binding reactions: implications for the tissue uptake of cobalamin

Plant lectins have been thought to impair nutrient absorption, both by specific and nonspecific interference in the absorptive process. The main objective of this investigation was to study the effect of lectins on the various binding reactions involving cobalamin (cbl)-protein complexes and their receptors, and to identify the rate-limiting step important in maintaining tissue levels of cobalamin. Among the lectins tested in vivo, only concanavalin A (ConA) was able to inhibit the transport of cobalamin to the tissues and caused a 70% to 75% inhibition of [(57)Co] cobalamin transported to the liver and kidney. The inhibition of transport to the tissues was independent of route of administration of cobalamin, whether intragastric or systemic, and was not due to decreased gastrointestinal uptake. When tested in vitro, concanavalin A inhibited the binding of transcobalamin II-cbl to its receptor, but not the binding of cobalamin to intrinsic factor or intrinsic factor-cobalamin complex to the ileal receptor. These results suggest that late events during transcellular transport of cobalamin through the enterocytes is the rate-limiting step determining tissue levels of cobalamin and that ConA inhibits these latter events.