The Vα14 invariant natural killer T cell TCR forces microbial glycolipids and CD1d into a conserved binding mode

The first crystal structures of iNKT cell TCRs bound to complexes of CD1d and microbe-derived glycolipids provide insight into the structural basis of iNKT cell microbial antigen recognition

Lipid and carbohydrate modifications of α-galactosylcer-amide differently influence mouse and human type I natural killer T cell activation

The ability of different glycosphingolipids (GSLs) to activate type I natural killer T cells (NKT cells) has been known for 2 decades. The possible therapeutic use of these GSLs has been studied in many ways; however, studies are needed in which the efficacy of promising GSLs is compared under identical conditions. Here, we compare five unique GSLs structurally derived from alpha-galactosylceramide. We employed biophysical and biological assays, as well as x-ray crystallography to study the impact of the chemical modifications of the antigen on type I NKT cell activation. Although all glycolipids are bound by the T cell receptor of type I NKT cells in real time binding assays with high affinity, only a few activate type INKT cells in in vivo or in vitro experiments. The differences in biological responses are likely a result of different pharmacokinetic properties of each lipid, which carry modifications at different parts of the molecule. Our results indicate a need to perform a variety of assays to ascertain the therapeutic potential of type I NKT cell GSL activators

Unique Interplay between Sugar and Lipid in Determining the Antigenic Potency of Bacterial Antigens for NKT Cells

Structural and biophysical studies reveal the induced-fit mechanism underlying the stringent specificity of invariant natural killer T cells for unique glycolipid antigens from the pathogen Streptococcus pneumoniae

Characteristics of Merkel Cell Polyomavirus T antigen oncoproteins.

Merkel cell polyomavirus (MCV) is the first polyomavirus that can cause human cancer, and was discovered in January of 2008 (Huichen Feng, 2008). Its large T antigen shares structural and sequential similarities with SV40 T antigen and functional similarities with Human Papillomavirus (HPV) E7 proteins. These viral proteins have tumor transforming ability by binding to the tumor suppressor protein Retinoblastoma (Rb). In HPV infected cells, E7 binds to Rb and disrupts the Rb-E2F complex. Accumulation of free E2F then induces p16 expression (Samir N. Khleif, et al. 1996). Our hypothesis was if MCV and SV40 T antigens use the same mechanism, we should be able to observe induced p16 expression in cells transfected with MCV and SV40 T antigen plasmids. The p16 expression in LNCap cells transfected with SV40 and MCV full-length and C-terminal truncated T antigen plasmids were detected by immunofluorescence and western blot. Increased p16 expression was only observed in MCV full-length T antigen but not in truncated MCV T antigen or SV40 T antigen transfected cells. The results might be associated with different effects of epigenetic modification by MCV and SV40 T antigens.Bachelor of Science in Biological Science

Anaesthesia and peri-interventional morbidity of rigid bronchoscopy: A retrospective analysis

Background: Rigid bronchoscopy is an invasive procedure that requires general anaesthesia with different ventilation strategies. Various mechanical and systemic complications can arise from the procedure and anaesthetic technique employed. The aim of this study is to evaluate the two common anaesthetic techniques and the peri-interventional morbidity of rigid bronchoscopy. Methods: We retrospectively analysed all the rigid bronchoscopies conducted in Singapore General Hospital between 1999 and 2014. Patient characteristics, type of procedures, type of anaesthesia, duration of procedure, ventilation strategies, various intra-operative medications, pre-operative and post-operative arterial blood gas, oxygen saturation and pulmonary function test, and peri-interventional complications were collected. Continuous data were reported as mean and categorical data were reported as percentages. Results: Majority of patients that underwent rigid bronchoscopy received total intravenous anaesthesia (81%). A significantly higher proportion of patients in the volatile groups were scheduled for biopsy (29.4%) using rigid bronchoscopy. Choice of ventilation strategies were largely similar in both groups. A higher complication rate of hypertension (11.8%), acute myocardial infarction (11.8%) and pneumothorax (17.6%) was seen in the volatile group. Conclusion: The choice of anaesthetic technique possibly affects the complication of patients undergoing rigid bronchoscopy. Volatile anaesthetics appeared to be driven by presumably shorter procedure, but was associated with higher systemic complication

Anesthetic techniques and haemodynamic control for Endoscopic Sinus Surgery: A retrospective analysis and review of literature

Introduction: Bleeding from mucosal edges is known to decrease surgical visibility and increase the risk of complications in Endoscopic sinus surgery (ESS). A variety of strategies, including modifying anesthetic techniques have been proposed to create a bloodless field. A recent survey in anesthesiologist revealed that a vast majority neither use controlled hypotension nor believe that modifying the anesthetic techniques will improve the outcome of ESS. This study investigates the different anesthetic techniques used for ESS and their effect on the haemodynamic variables achieved intra-operatively. Methods: Data were retrospectively collected from an electronic anesthesia database on 233 consecutive adult patients who underwent endoscopic sinus surgery in a tertiary hospital in Singapore from January 2014 to August 2015 and statistical analysis was performed using SPSS. Results: Inhaled anesthetics (IA) were used for 93% (49% with morphine or fentanyl, 42% with remifentanil) and total intravenous anesthesia (TIVA) for 7% of the cases respectively. The airway was secured with endotracheal tube in 94.6% and the rest were having LMA. Average Mean Arterial Pressure (MAP) lower than 70 mmHg was achieved in 74.4%. Antihypertensive drugs were used only in 5 cases (2.3%). Distribution of intra operative MAP and Heart rate (HR) were similar among different anesthetic techniques. Lowest MAP and HR achieved were significantly lower in IA with remifentanil use. Conclusion: Inhaled anesthesia is the preferred maintenance technique used for ESS. The desired MAP range was achieved in about 75% of the cases without needing anti hypertensives. Use of remifentanil reduces the MAP and HR further which might potentially improve the quality of surgical field and the outcome

Structural basis for the recognition of C20:2-αGalCer by the invariant natural killer T-cell receptor-like antibody L363

Natural killer T (NKT) cells express a semi-invariant V alpha 14T cell receptor (TCR) and recognize structurally diverse antigens presented by the antigen-presenting molecule CD1d that range from phosphoglycerolipids to alpha- and beta-anomeric glycosphingolipids, as well as microbial alpha-glycosyl diacylglycerolipids. Recently developed antibodies that are specific for the complex of the prototypical invariant NKT (iNKT) cell antigen alpha GalCer (KRN7000) bound to mouse CD1d have become valuable tools in elucidating the mechanism of antigen loading and presentation. Here, we report the 3.1 angstrom resolution crystal structure of the Fab of one of these antibodies, L363, bound to mCD1d complexed with the alpha GalCer analog C20:2, revealing that L363 is an iNKT TCR-like antibody that binds CD1d-presented alpha GalCer in a manner similar to the TCR. The structure reveals that L363 depends on both the L and H chains for binding to the glycolipid-mCD1d complex, although only the L chain is involved in contacts with the glycolipid antigen. The H chain of L363 features residue Trp-104, which mimics the TCR CDR3 alpha residue Leu-99, which is crucial for CD1d binding. We characterized the antigen-specificity of L363 toward several different glycolipids, demonstrating that whereas the TCR can induce structural changes in both antigen and CD1d to recognize disparate lipid antigens, the antibody L363 can only induce the F' roof formation in CD1d but fails to reorient the glycolipid headgroup necessary for binding. In summary, L363 is a powerful tool to study mechanism of iNKT cell activation for structural analogs of KRN7000, and our study can aid in the design of antibodies with altered antigen specificity