[Influence of class number and class size on the formation of indistinct classes of configural objects].
Explore the source record for details and available documents.
Discrimination Learning↗
SEARCH · PubMed Health
Results for “Class”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Expression of class I and class II major histocompatibility complex antigens on human hepatocytes.
We analyzed whether normal human hepatocytes, which normally do not display Class II major histocompatibility complex antigens, can be induced to express them in vitro, and whether this induction has an in vivo counterpart in chronic liver diseases. While both alpha- and gamma-interferon induced expression of Class I antigens, only gamma-interferon induced expression of Class II antigens on hepatocytes in vitro. Recombinant interleukin 2 had no effect on major histocompatibility complex antigen expression. Both Class I and Class II antigens could be detected by indirect immunofluorescence on hepatocytes from patients with various forms of chronic liver disease, regardless of etiology. These findings suggest that gamma-interferon produced by T lymphocytes that infiltrate the liver during the course of chronic hepatitis induces Class II major histocompatibility complex antigen expression and may endow the hepatocytes with the capacity to perform accessory (antigen-presenting) cell functions.
Antibodies, Monoclonal↗
Shifting substrate specificity of human glutathione transferase (from class Pi to class alpha) by a single point mutation.
Substrate selectivity, among glutathione transferase (GST) isoenzymes, appears to be determined by a few residues. As part of study to determine which residues are class-specific determinants, Tyr 108 (an important residue of the class Pi) has been changed to a valine, the structural equivalent of a class Alpha enzyme. Using a panel of selected substrates, "diagnostic" for either class Pi or Alpha, it is shown here that this single mutation significantly alters the catalytic properties of the class Pi enzyme and shifts the substrate specificity of the enzyme toward that of the class Alpha enzyme.
Amino Acid Sequence↗
Effect of E-4031, a new class III antiarrhythmic drug, on reentrant ventricular arrhythmias: comparison with conventional class I drugs.
We evaluated the antiarrhythmic efficacy of E-4031, a new class III drug, and compared it with that of conventional class I and II antiarrhythmic agents in terms of electrophysiological actions on refractoriness and conduction in a 7-day-old canine model of myocardial infarction. Sustained monomorphic VT was reproducibly induced in 26 dogs by a premature stimulation method from the right ventricle. Class I drugs (disopyramide, aprindine, flecainide) prevented VT induction in 5 of 13 dogs, and propranolol and E-4031 prevented it in 6 of 6 and 6 of 7 dogs, respectively. The effective refractory period (ERP) was determined at 47 epicardial sites overlying the infarct in each experiment by a S1S2 method. The standard deviation (SD) of the mean ERP of these sites was used as an index of ERP dispersion. The extent of ERP prolongation produced by class I drugs and E-4031 was significantly more marked than that produced by propranolol. However, the SD was increased by class I drugs and E-4031, but not by propranolol. Class I drugs increased the ERP dispersion mainly by an effect on the transmural infarct zone in which the control ERP was more prolonged than in the normal zone. E-4031 tended to prolong the ERP in both the normal and infarct zones, and had a minimal tendency to increase ERP dispersion. In contrast, propranolol decreased the ERP dispersion between zones. Conduction velocity calculated by epicardial mapping was significantly decreased by flecainide, but not by E-4031. We conclude that the antiarrhythmic effect of E-4031 depends largely on its ability to prolong refractoriness without suppressing conduction.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Class I and class II ribonuclease H activities in Crithidia fasciculata (Protozoa).
The protozoan Crithidia fasciculata contains two different ribonuclease H activities. These enzymes display similar physical and biochemical characteristics to their homologues in higher eukaryotes, for instance calf thymus class I and class II ribonuclease H. Class I ribonuclease H of lower and higher eukaryotes can be activated by Mg2(+)- and Mn2(+)-ions. However, the presence of Mn2(+)-ions is inhibitory for the Mg2(+)-dependent class II ribonuclease H activity of Crithidia fasciculata and calf thymus. The protozoan class I-homologue enzyme appears to be serologically related to the class I ribonuclease H of calf thymus.
Animals↗
A novel spin-label for study of membrane protein rotational diffusion using saturation transfer electron spin resonance. Application to selectively labelled class I and class II-SH groups of the shark rectal gland Na+/K+-ATPase.
Na+/K+-ATPase in membranous preparations from the rectal gland of Squalus acanthias has been spin-labelled either on Class I -SH groups, which maintain overall ATPase activity, or on Class II -SH groups, for which only phosphorylation activity is preserved. Labelling of the Class I groups requires solubilization of the membranes and subsequent reconstitution by precipitation with Mn2+ in order to remove contaminating peripheral proteins, which are also labelled. Control experiments with preparations in which the Class II groups are labelled demonstrate that the mobility and aggregation state of the enzyme in the reconstituted membranes are similar to those in the native membrane. Both the conventional maleimide nitroxide derivative and a new benzoylvinyl nitroxide derivative have been used for the labelling. The segmental mobility of the labels and the overall rotational diffusion of the labelled protein have been investigated using saturation transfer ESR spectroscopy. The benzoylvinyl spin-label derivative offers particular advantages for the study of the protein rotational mobility in that the segmental mobility is considerably reduced relative to that observed with the maleimide derivative. This is especially the case for the Class I groups, where the maleimide label exhibits pronounced segmental mobility. Comparison of the results from the two labels indicates that the integral of the saturation-transfer spectrum is much more sensitive to segmental motion than are the diagnostic line-height ratios. This fact allows a better level of discrimination between the two types of motion. The results from the benzoylvinyl nitroxide-labelled Class I groups suggest that the Na+/K+-ATPase is probably present as an (alpha beta)2-diprotomer (or higher oligomer) in the native membrane.
Animals↗
A survey of a functional amino acid of class C beta-lactamase corresponding to Glu166 of class A beta-lactamases.
The class C beta-lactamase of Citrobacter freundii GN346 is a typical cephalosporinase comprising 361 amino acids. The aspartic acid at position 217 and glutamic acid at position 219 in this beta-lactamase were, respectively, previously shown not to be the counterpart of Glu166 (ABL166) in class A beta-lactamases, even though sequence alignment of class A and C enzymes strongly suggested this possibility [(1990) FEBS Lett. 264, 211-214; (1990) J. Bacteriol. 172, 4348-4351]. We tried again to assign candidates for the counterpart of Glu166 through sequence alignment based on other criteria, the glutamic acids at positions 195 and 205 in the class C beta-lactamase being selected. To investigate this possibility, these two glutamic acids were changed to glutamine, lysine or alanine, respectively. All the mutant enzymes showed more than 50% of the activity of the wild-type enzyme, indicating that the possibility was ruled out. These results strongly suggested the possibility that the class C beta-lactamase lacks a functional acidic residue corresponding to Glu166 in class A enzymes.
Alanine↗
A rapid and reliable in vivo method for anti-GPLA (class I and class II antigens) antibody titration and GPLA typing.
A reverse Arthus reaction (RAR) may be successfully used in guinea pigs to detect histocompatibility alloantigens of the GPLA type. Epidermal cells carry class I GPLA antigens, and Langerhans cells also bear class II alloantigens. It is therefore possible to elicit an RAR by intradermal injection of relevant alloimmune sera in the skin of guinea pigs of known GPLA haplotype. RAR is detected by increased vascular permeability due to IgG1 antibody and hemorrhage due to IgG2 antibody. Compared with an in vitro protein A-rosetting method RAR is easier and quicker. It proved more sensitive for class II antigens in which Langerhans cells are the target for anti-class II antibody and rather less sensitive for class I antigens. RAR is a convenient method for following the course of GPLA alloimmunization, allowing titration of antibodies against both classes of antigen. It may also be used to type guinea pigs of unknown GPLA haplotype.
Animals↗
Abnormal expression of class II MHC antigens in placentae from patients with pemphigoid gestationis: analysis of class II MHC subregion product expression.
Abnormal expression of class II MHC antigens was consistently observed in an immunohistological study on placentae from patients with pemphigoid gestationis. The area affected in all the placentae was the chorionic villi adjacent to the maternal decidua. The villous stroma, and in some cases the chorionic fetal endothelium, had abnormal expression of class II MHC antigens. Monoclonal antibodies specific for the class II MHC subregion products (DR, DP and DQ) were used to analyse the class II MHC antigen expression. Differential expression of the class II MHC subregion products was observed on the villous stroma and chorionic fetal endothelium; DR and DP were always expressed but DQ in some cases was heterogeneous. This abnormal expression of class II MHC antigens may reflect an immunological attack on the placenta in pemphigoid gestationis.
Antibodies, Monoclonal↗
Multiple sclerosis: relevance of class I and class II MHC-expressing cells to lesion development.
Expression of Class I (HLA-ABC) and Class II (HLA-Dr; Ia) major histocompatibility (MHC) antigens on endothelial cells and astrocytes was investigated in multiple sclerosis (MS) lesions of variable disease activity and in normal central nervous system (CNS) using immunocytochemical techniques. Findings were correlated to lesion pathology and to the presence and distribution of T cells, T cell subsets, and interleukin-2 (IL-2) receptor-bearing cells. HLA-ABC was present on virtually all endothelial cells in normal and pathologic tissue samples. Ia was absent from controls and was detectable on about 10% of CNS endothelial cells in MS. In normal CNS, astrocytes were Ia-negative and rarely expressed HLA-ABC. In MS, Class I and II MHC-positive astrocytes were found, and both displayed a high frequency in active lesions. Class I-reactive glia were primarily associated with T cell infiltrates and were less common in older lesions in which macrophages predominated. In contrast, Class II-positive astrocytes were found in all active MS lesions independent of the composition of inflammatory cells. Expression of HLA-ABC and Ia molecules on astrocytes in MS lesions could indicate their involvement in local presentation of antigen to cytotoxic (T8+) and helper/inducer (T4+) T cells, respectively. The observed distinct distribution patterns of HLA-ABC and Ia-positive astrocytes might suggest that cytotoxic T8+ cells are operative early during lesion development in MS. This could be followed by a more extensive Class II MHC-restricted helper T cell-mediated immune response which leads to selective destruction of myelin via activated macrophages.
Antibodies, Monoclonal↗
The HLA-class II-associated chondroitin sulfate proteoglycan expressed by class II positive T and monocyte-like cell lines is larger than that expressed by EBV-transformed B-lymphoblastoid cell lines.
The human class II-associated chondroitin sulfate proteoglycan (CSPG) was originally detected as an approximately 40-70 kd species from normal human tonsil cells and Epstein-Barr virus (EBV) transformed B-lymphoblastoid cell lines. The identification of the invariant chain as the core protein of the CSPG allowed us to directly assay for the CSPG on both class II positive and negative immunocompetent cells of other lineages. Our results indicate that the CSPG is present on the class II-positive monocyte-like cell line U937 and T-cell line HUT-102, but not on the class-II negative T-cell line CCRF/CEM. No class II positive cells were found that did not also express the CSPG. The expression of the CSPG on U937 cells is increased after stimulation with gamma-interferon and PMA, paralleling the previously described increase in class II and invariant chain expression. In addition, the CSPGs from U937, HUT-102, and Raji, all cell lines derived from human malignancies, migrate as an approximately 55-90 kd species, larger than the CSPG previously characterized. However, the core proteins of the CSPG from all cells studied appear as two bands of 38 and 28 kd, indicating the size difference in the CSPG is attributable to differences in the glycosaminoglycan chains.
B-Lymphocytes↗
Human allograft-derived T-cell lines: donor class I- and class II-directed cytotoxicity and repertoire stability in sequential biopsies.
In order to characterize directly the T-cell repertoire utilized in human renal allograft rejection, we analyzed 20 long-term T-cell lines established from lymphocytic infiltrates present in renal tissue obtained by needle biopsy from transplant patients with rejection indications. All cell lines are strongly cytotoxic against one or more of the HLA antigens for which the kidney donor and the recipient were mismatched. Traditionally, cytotoxicity in allograft rejection has been attributed to CD8-positive cytotoxic T lymphocytes (CTLs) directed against class I alloantigens. Cell lines described here are mixtures of distinct CD4-antigen-positive and CD8-antigen-positive subpopulations, and exhibit class I- as well as class II-directed killing. Using a cell line that demonstrates class II-directed cytotoxicity and a set of class II deletion mutants as target cells, we show that class II antigens, in particular HLA-DP, can serve as targets in renal allograft rejection. The role of CD4-positive CTLs was shown by analysis of clonal populations or sorted CD8-positive and CD4-positive subpopulations. In several instances we have obtained cell lines from serial biopsies performed on the same patient at distinct time points during an ongoing rejection. Comparisons of the phenotype, function, and specificities allow for speculation regarding T-cell population dynamics within the rejection response.
Antigens, Differentiation, T-Lymphocyte↗
An HLA class I peptide-binding assay based on competition for binding to class I molecules on intact human B cells. Identification of conserved HIV-1 polymerase peptides binding to HLA-A*0301.
A peptide-binding assay employing the HLA class I molecules on intact human B cells is described. The peptide antigens are stripped from the HLA class I molecules by mild acid treatment, after which the cells are incubated with a FL-labeled reference peptide together with different concentrations of the peptide of interest. The effectiveness by which the latter peptide competes for binding to the HLA class I molecules is assayed by measuring the amount of HLA-bound FL-labeled reference peptide with FACscan analysis. The assay is easy to perform because there is no need to purify HLA class I molecules, or to transfect cells with HLA class I molecules, and no radioactive label is used. Moreover, large panels of HLA-typed human B-cell lines are available as tools for peptide binding to a vast array of HLA molecules. The binding assay was optimized and validated with peptides of known binding capacity to either HLA-A*0201 or HLA-A*0301. The kinetics of peptide binding in this assay were shown to be comparable to that in assays employing soluble HLA class I molecules. Application of the assay in the search for potential HLA-A*0301 restricted CTL epitopes, derived from HIV-1 polymerase, resulted in the identification of five high-affinity binding peptides.
Amino Acid Sequence↗
Protective efficacy of monoclonal antibodies to class 1 and class 3 outer membrane proteins of Neisseria meningitidis B:15:P1.16 in infant rat infection model: new prospects for vaccine development.
The protective efficacy of monoclonal antibodies to class 1 and class 3 outer membrane proteins of Neisseria meningitidis B:15:P1.16 was tested in an infant rat infection model. Four monoclonal antibodies to class 1 protein had bactericidal titres exceeding 20,000 and they protected infant rats completely against bacterial challenge with meningococci carrying the same class 1 protein, P1.16. One monoclonal antibody to class 3 protein was highly bactericidal (titer greater than 20,000), whereas two others had no bactericidal activity. All these antibodies gave some protection from infection, resulting in mortalities varying from 66 to 83% as compared to 100% in control rats who had received either unrelated monoclonal antibody or saline. These results strongly speak for class 1 outer membrane protein as a vaccine candidate for meningococcus group B.
Animals↗
Comparison of psychosocial status in treatment-seeking women with class III vs. class I-II obesity.
OBJECTIVE: This study compared the psychosocial status and weight loss expectations of women with extreme (class III) obesity who sought bariatric surgery with those of women with class I-II obesity who enrolled in a research study on behavioral weight control. RESEARCH METHODS AND PROCEDURES: Before treatment, all participants completed the Beck Depression Inventory-II and the Weight and Lifestyle Inventory. This latter questionnaire assesses several domains including symptoms of depression and low self-esteem, history of psychiatric complications, current stressors, and weight loss expectations. RESULTS: Women with class III obesity, as compared with class I-II, reported significantly more symptoms of depression. Fully 25% of women in the former group appeared to have a significant mood disorder that would benefit from treatment. As compared with women with class I-II obesity, significantly more women with class III obesity also reported a history of psychiatric complications, which included physical and sexual abuse and greater stress related to their physical health and financial/legal matters. Both groups of women had unrealistic weight loss expectations. Those who sought surgery expected to lose 47.6 +/- 9.3% of initial weight, compared with 24.8 +/- 8.7% for those who enrolled in behavioral weight control. DISCUSSION: These findings suggest that women with extreme obesity who seek bariatric surgery should be screened for psychosocial complications. Those determined to have significant psychiatric distress should be referred for behavioral or pharmacological treatment to alleviate their suffering. Long-term studies are needed to provide definitive guidance concerning the relationship between preoperative psychopathology and the outcome of bariatric surgery.
Adult↗
Chloroplast class I and class II aldolases are bifunctional for fructose-1,6-biphosphate and sedoheptulose-1,7-biphosphate cleavage in the Calvin cycle.
Class I and class II aldolases are products of two evolutionary non-related gene families. The cytosol and chloroplast enzymes of higher plants are of the class I type, the latter being bifunctional for fructose-1,6- and sedoheptulose-1,7-P2 in the Calvin cycle. Recently, class II aldolases were detected for the cytosol and chloroplasts of the lower alga Cyanophora paradoxa. The respective chloroplast enzyme has been shown here to be also bifunctional for fructose-1,6- and sedoheptulose-1,7-P2. Kinetics, also including fructose-1-P, were determined for all these enzymes. Apparently, aldolases are multifunctional enzymes, irrespective of their class I or class II type.
Cell Compartmentation↗
Class I chitinases with hevein-like domain, but not class II enzymes, are relevant chestnut and avocado allergens.
BACKGROUND: Several foods associated with the latex-fruit syndrome present relevant allergens of around 30 kd. Neither these components nor any other responsible for the reported cross-reactions have been identified and purified. OBJECTIVE: We sought to isolate and characterize the 30 kd allergens from avocado fruit and chestnut seed, two of the main allergenic foods linked with latex allergy. METHODS: Sera from patients allergic to chestnut and avocado were selected according to clinical symptoms, specific IgE levels, and positive skin prick test responses. Class I and II chitinases were purified by affinity and cation-exchange chromatography and characterized by specific IgE and anti-chitinase immunodetection, immunoblot inhibition assays, enzymatic activity tests, and N-terminal sequencing. RESULTS: Relevant 32 kd allergens were detected by specific IgE immunodetection in both avocado and chestnut crude extracts. The same bands, together with others of 25 kd, were revealed by a monospecific antiserum against class II chitinases. Purification and characterization of the 32 kd allergens from both plant sources allowed their identification as class I chitinases with an N-terminal hevein-domain. The purified allergens fully inhibited IgE binding by the corresponding crude extract when tested in immunoblot inhibition assays. Highly related 25 kd class II chitinases that lack the hevein-like domain were also isolated from the same protein preparations. No IgE-binding capacity was shown by these class II enzymes. CONCLUSION: Class I chitinases are relevant allergens of avocado and chestnut and could be the panallergens responsible for the latex-fruit syndrome. The hevein-like domain seems to be involved in their allergenic reactivity.
Adult↗
Association with HLA class I in Epstein-Barr-virus-positive and with HLA class III in Epstein-Barr-virus-negative Hodgkin's lymphoma.
BACKGROUND: Associations of Hodgkin's lymphoma with HLA have been reported for many years. In 20-40% of patients with this disorder, Epstein-Barr virus (EBV) is present in the neoplastic cells. Because presentation of EBV antigenic peptides can elicit vigorous immune responses, we investigated associations of the HLA region with EBV-positive and EBV-negative Hodgkin's lymphoma. METHODS: In a retrospective, population-based study, patients with Hodgkin's lymphoma were reclassified according to the WHO classification, and EBV status was assessed by in-situ hybridisation of EBV-encoded small RNAs. Germline DNA was isolated from 200 patients diagnosed between 1987 and 2000 and from their first-degree relatives. Genotyping was done with 33 microsatellite markers spanning the entire HLA region and two single-nucleotide polymorphisms in the genes for tumour necrosis factor alpha and beta. Classic association analysis and the haplotype sharing statistic were used to compare patients with controls. FINDINGS: Classic association analysis (but not the haplotype sharing statistic) showed an association of consecutive markers D6S265 and D6S510 (p=0.0002 and 0.0003), located in the HLA class I region, with EBV-positive lymphomas. The haplotype sharing statistic (but not classic association analysis) showed a significant difference in mean haplotype sharing between patients and controls surrounding marker D6S273 (p=0.00003), located in HLA class III. INTERPRETATION: Areas within the HLA class I and class III regions are associated with susceptibility to Hodgkin's lymphoma, the association with class I being specific for EBV-positive disease. This finding strongly suggests that antigenic presentation of EBV-derived peptides is involved in the pathogenesis of EBV-involved Hodgkin's lymphoma. RELEVANCE TO PRACTICE: Polymorphisms in the HLA region could explain ethnic variation in the incidence of Hodgkin's lymphoma. The association of EBV-positive Hodgkin's lymphoma with HLA class I suggests that this polymorphism might affect the proper presentation of EBV antigens to cytotoxic T lymphocytes.
Adolescent↗