Role of membrane environment and membrane-spanning protein regions in assembly and function of the Class II Major Histocompatibility complex

Class II Major Histocompatibility complex (MHC-II) is a polymorphic heterodimer that binds antigen-derived peptides and presents them on the surface of antigen presenting cells. This mechanism of antigen presentation leads to recognition by CD4 T-cells and T-cell activation, making it a critical element of adaptive immune response. For this reason, the structural determinants of MHC-II function have been of great interest for the past 30 years, resulting in a robust structural understanding of the extracellular regions of the complex. However, the membrane-localized regions have also been strongly implicated in protein-protein and protein-lipid interactions that facilitate Class II assembly, transport and function, and it is these regions that are the focus of this review. Here we describe studies that reveal the strong and selective interactions between the transmembrane domains of the MHC α, and invariant chains which, when altered, have broad reaching impacts on antigen presentation and Class II function. We also summarize work that clearly demonstrates the link between membrane lipid composition (particularly the presence of cholesterol) and MHC-II conformation, subsequent peptide binding, and downstream T-cell activation. We have integrated these studies into a comprehensive view of Class II transmembrane domain biology.     

Applying the chronic care model to prenatal care: Patient activation,productive interactions,and prenatal outcomes

Objective

To demonstrate how the chronic care model can be applied in prenatal care.

Preparation and storage characteristics of white cell-reduced high-concentration platelet concentrates collected by anapheresis system for transfusions in utero

BACKGROUND: Important concerns with regard to in utero platelet transfusions are avoidance of volume overload and the immunomodulatory effects of residual white cells (WBCs). This study evaluated a modification of a leukocyte‐reduction system (LRS, Spectra, COBE BCT) for apheresis, which collects high‐concentration WBC‐reduced platelets (HCPs) for in utero transfusion. STUDY DESIGN AND METHODS: The LRS procedure was modified by running the platelet collection pump at specified low flow rates (Q_col) for the first part of the procedure, collecting HCPs by gently purging them from the LRS chamber into a designated collection bag and then restoring the original LRS procedure settings to collect a second standard apheresis platelet concentrate (PC). Two centers carried out 32 procedures. Platelet yield, residual WBCs, and in vitro platelet function studies were evaluated. RESULTS: Platelet concentrations in 60 mL of HCPs were predictable according to Q_col (r² = 0.735). HCP yields varied from 0.9 to 3.2 × 10¹¹, depending on the desired final platelet concentrations in 60 mL, with an overall average of 1.92 × 10¹¹ (n = 32). Apheresis PCs had a mean platelet yield of 2.9 × 10¹¹ (1.3‐4.4 × 10¹¹, n = 20) and 3.9 × 10¹¹ (2.2‐5.8 × 10¹¹, n = 12) at concentrations of 1.3 × 10¹² per L for single‐needle and dual‐ needle procedures, respectively. Median WBC counts were 5.6 × 10³ for HCPs and 2.0 × 10⁴ for apheresis PCs, with >99 percent expected to be less than 1 × 10⁶. HCP in vitro characteristics were equivalent to those of apheresis PCs at 24 hours after collection. In vitro performance declined over storage as a function of HCP yield. HCP pH at 22^oC was maintained at a level of >6.2 for more than 3 days for yields >1.6 × 10¹¹, less than 2 days for yields 1.6 to 2.2 × 10¹¹, and less than 24 hours for yields >2.2 × 10¹¹. HCPs showed good in vitro characteristics and could be stored for 1 to 3 days, depending on the total number of platelets collected. CONCLUSION: A standard apheresis PC and an HCP requiring no secondary processing can be collected with the Spectra LRS. The platelet concentration may be determined by clinical need. HCPs meet the requirements for components that are transfused in utero.     

Characteristics of bacterial infections and prevalence of multidrug-resistant bacteria in hospitalized patients with liver cirrhosis in Germany

Introduction and ObjectivesBacterial infections are associated with a dismal prognosis in patients with liver cirrhosis. Data on their prevalence and the associated pathogen spectra in Germany are scarce. This study aimed to evaluate the impact of bacterial infections on mortality in hospitalized patients with liver cirrhosis and to analyze the prevalence of multidrug-resistant (MDR) bacteria in a German tertiary care center.Patients and MethodsConsecutive, non-electively hospitalized patients with liver cirrhosis were enrolled in this study between 03/2019-06/2021. All patients underwent clinical, laboratory and microbiological testing to detect potential bacterial infections. Patients were followed for 30 days regarding the composite endpoint of death or liver transplantation (mortality).ResultsIn total, 239 patients were recruited (median MELD 18). Bacterial infection was detected in 81 patients (33.9%) at study inclusion. A total of 70 patients (29.3%) developed a hospital-acquired infection. When comparing community-acquired and hospital-acquired infections, the pathogen pattern shifted from a gram-negative to a more gram-positive spectrum and showed an increase of Staphylococcus spp.. MDR bacteria were detected in seven infected patients (5.8%). 34 patients reached the composite endpoint during 30-days follow-up. In multivariable logistic regression analysis, the presence of infection during hospitalization remained independently associated with higher mortality (OR 2.522, 95% CI 1.044 - 6.091, p = 0.040).ConclusionsThis study demonstrates that bacterial infections are common in hospitalized patients with liver cirrhosis in Germany and are a major determinant of short-term mortality. Our data highlight the importance of regional differences in MDR bacteria and may guide physicians' decision-making regarding calculated antibiotic treatment.     

肝硬化患者血浆前脑利钠肽水平变化及其临床意义

目的探讨血浆前脑利钠肽（proBNP）对肝硬化心肌病的判断价值。方法对38例肝硬化患者（LC组）和20名健康体检者（CG组），用ELISA法测定血浆proBNP水平，并行心电图检查。比较两组proBNP水平及心电图改变（QTc、QTd、QTcd和Pd）的差异；对肝硬化患者，分析心电图改变与CTP积分、MELD评分、proBNP的关系。结果Lc组proBNP水平为（228．0±83．4）fmol／ml，显著高于CG组（127．4±21．1）fmol／ml。LC组QTc、QTd、QTcd、Pd分别为（446．9±28．0）ms1/2、（36．4±6．6）ms、（40．6±9．0）ms1/2、（22．8±4．8）ms，均显著长于CG组（417．2±21．5）ms1/2、（29．6±4．9）ms、（31．1±4．9）ms1/2、（19．0±4．1）ms，且与CTP、MELD、proBNP水平呈正相关。结论肝硬化患者存在心肌受损，血浆proBNP可较好地反映肝硬化心肌病病情。     

The cytotoxic effects of Scilla nervosa (Burch.) Jessop (Hyacinthaceae) aqueous extract on cultured HepG2 cells

Ethnopharmacological relevance

Bulbs of Scilla nervosa, a medicinal plant indigenous to Southern Africa, are traditionally used in aqueous decoctions to treat a diverse range of illnesses. The bulbs contain homoisoflavanones and stilbenoids. Little information is known about the plant's toxicity on the liver, a major detoxifying organ. This study investigated the effects of an aqueous extract of the bulbs in cultured HepG2 liver cells, a model system for investigating the toxicity of xenobiotics.

Materials and methods

The concentration that reduced cell viability to 50% (IC₅₀) after 24 h treatment was derived. Potential mechanisms of toxicity using the IC₅₀ were investigated as changes in metabolic activity, apoptosis, oxidative damage and DNA fragmentation. In addition, cytochrome P450 3A4 (CYP3A4) activity, which is implicated in drug metabolism and interactions, was also assayed.

Results

Cell viability decreased in a concentration-dependent manner and the IC₅₀ was determined as 0.03 mg/mL. Treating the cells at the IC₅₀ for 24 h resulted in increased intracellular ATP levels, no significant change in phosphatidylserine externalisation, increased caspase-8 activity, decreased caspase-9 activity, no significant change in mitochondrial membrane potential, increased lipid peroxidation, evidence for genotoxicity as demonstrated by DNA fragmentation, and slightly induced CYP3A4 activity.

Conclusion

Results suggest that liver cells are sensitive to an aqueous extract of the bulbs and there is an increased potential to induce apoptosis, oxidative stress and genotoxicity in vitro.