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PubMed2003

Class 1 and class 2 integrons in poultry carcasses from broiler house and poultry processing environments.

Integrons have been identified as major genetic contributors to the dissemination of antimicrobial resistance in bacteria. The objective of this study was to examine the prevalence of integrons in poultry processing at the broiler house and in processing plants. Class 1 and class 2 integrons were found throughout the processing environment. Of the two classes of integrons, class 1 was the most prevalent in all processing areas. The levels of both classes of integrons decreased from the farm to the processing plant. Within the chiller tank in the processing plant, the persistence of these sequences appears to be related to the free chlorine concentration of the chiller tank water. The variable regions of the amplified integrons showed size diversity (from 680 to 2,000 bp), suggesting diversity in types of antibiotic-resistance-coding gene cassettes. The presence of the class 1 and class 2 integrons in the chlorinated chiller tank suggests that these sequences are capable of withstanding this critical step in the reduction of microbial loads on poultry carcasses. The persistence of the integron gene sequences on the farm and throughout processing highlights the stability of these transmissible antibiotic-resistance-coding nucleotide sequences and their potential role as reservoirs of antibiotic-resistance-coding genetic elements within the poultry rearing and processing environments.

Animals↗

PubMed2003

The BEST study--a prospective study to compare business class versus economy class air travel as a cause of thrombosis.

BACKGROUND: As many as 10% of airline passengers travelling without prophylaxis for long distances may develop a venous thrombosis. There is, however, no evidence that economy class travellers are at increased risk of thrombosis. OBJECTIVES: A suitably powered prospective study, based on the incidence of deep-vein thrombosis (DVT) reported in previous studies on long-haul flights, was designed to determine the incidence of positive venous duplex scans and D-dimer elevations in low and intermediate-risk passengers, comparing passengers travelling in business and economy class. PATIENTS/METHODS: Eight hundred and ninety-nine passengers were recruited (180 travelling business class and 719 travelling economy). D-dimers were measured before and after the flight. A value greater than 500 ng/ml was accepted as abnormal. A thrombophilia screen was conducted which included the factor V Leiden mutation, the prothombin 20210A mutation, protein C and S levels, antithrombin levels, and anticardiolipin antibodies immunoglobulin G (IgG) and immunoglobulin M (IgM). On arrival, lower limb compression ultrasonography of the deep veins was performed. Logistical regression analysis was used to determine the risk factors related to abnormally high D-dimer levels. RESULTS: Only 434 subjects had a full venous duplex scan performed. None had ultrasonic evidence of venous thrombosis. Nine passengers tested at departure had elevated D-dimer levels and these volunteers were excluded from further study. Seventy-four of the 899 passengers had raised D-dimers on arrival. Twenty-two of 180 business class passengers (12%) developed elevated D-dimers compared with 52 of 719 economy class passengers (7%). There was no significant association between elevation of D-dimers and the class flown (odds ratio (OR) 0.61, p = 0.109). The factor V Leiden mutation, factor VIII levels and the use of aspirin were, however, associated with raised D-dimers (OR 3.36, p = 0.024; OR 1.01, p = 0.014; and OR 2.04, p = 0.038, respectively). Five hundred and five passengers were contacted within 6 months and none reported any symptoms of a clinical thrombosis or pulmonary embolus. CONCLUSION: The incidence of ultrasonically proven DVT is much lower than previously reported. However, more than 10% of all passengers developed raised D-dimers, which were unrelated to the class flown. A rise in D-dimers is associated with an inherent risk of thrombosis and/or thrombophilia, demonstrates activation of both the coagulation and fibrinolytic systems during long-haul flights, and may indicate the development of small thrombi.

Adult↗

PubMed1988

Analysis of the molecular specificities of anti-class II monoclonal antibodies by using L cell transfectants expressing HLA class II molecules.

Expressible HLA class II alpha- and beta-chain cDNA were used for DNA-mediated gene transfer to produce L cell transfectants expressing single types of human class II molecules. Cloned transfectants expressing nine different class II molecules were isolated: DR alpha: DR1 beta I, DR alpha: DR4 beta I, DR alpha: DR5 beta I, DR alpha: DR5 beta III (DRw52), DR alpha: DR7 beta I, DR alpha: DR4/7 beta IV (DRw53), DQ7 alpha: DQw2 beta, DQ7 alpha: DQw3 beta, and DPw4 alpha: DPw4 beta. These class II-expressing transfectants were used to analyze by flow cytometry the molecular specificities of 20 anti-class II mAb. These analyes indicate that some mAb are more broadly reactive than was previously thought based on immunochemical studies. In contrast, the narrow molecular specificities of other anti-class II mAb were confirmed by this approach. Transfectants expressing human class II molecules should be valuable reagents for studies of B cell and T cell defined epitopes on these molecules.

Animals↗

PubMed1983

Evidence implicating L3T4 in class II MHC antigen reactivity; monoclonal antibody GK1.5 (anti-L3T4a) blocks class II MHC antigen-specific proliferation, release of lymphokines, and binding by cloned murine helper T lymphocyte lines.

Monoclonal antibody GK1.5 recognizes a determinant, designated L3T4a, on the murine T cell surface molecule L3T4. The expression of L3T4a by functional murine T cell clones appears to correlate primarily with class II MHC antigen reactivity rather than with functional phenotype. In previous studies, antigen-specific cytolysis by a cloned class II MHC antigen(I-Ak)-reactive CTL line was found to be blocked entirely by monoclonal antibody (mAb) GK1.5, at a step before the lethal hit. In the present studies, we demonstrate that mAb GK1.5 profoundly blocks antigen-specific proliferation and release of lymphokines by cloned murine class II MHC antigen-reactive helper T lymphocyte (HTL) lines. Analysis of cloned T cell hybridomas, however, suggests that there exists clonal heterogeneity in the degree of inhibition of class II MHC antigen-specific function by mAb GK 1.5. Finally, we present evidence that mAb GK1.5 blocks class II MHC antigen-specific function by blocking class II MHC antigen-specific binding. The data presented here lend considerable support to the concept both that L3T4 and the human Leu-3/T4 molecules are similar and that L3T4 plays a role in class II MHC antigen-reactivity by murine T cells.

Animals↗

PubMed1989

Demonstration by class I gene transfer that reduced susceptibility of human cells to natural killer cell-mediated lysis is inversely correlated with HLA class I antigen expression.

HLA antigen-loss mutants and class I gene transferents were used to analyze the influence of class I expression on natural killer (NK) cell-mediated lysis. Only HLA antigen-loss mutants that had lost expression of either HLA-A and HLA-B antigens (mutant .184) or of HLA-A, B and C antigens (mutant .221) were distinctly susceptible to NK-mediated lysis. Mutants with reduced expression of class II antigens but unaltered expression of class I antigens remained resistant to NK lysis. A direct demonstration of the effect of class I antigen expression on human cells was made by analyzing a variety of gene transferents of the HLA-A, B, C null mutant .221 expressing only one transferred HLA-A, B or C gene. These results specifically show that expression of class I antigens, with a possible preferential effect of HLA-B expression, reduces the susceptibility of mutant .221 to NK-mediated lysis.

Cytotoxicity, Immunologic↗

PubMed1997

The T/B cell interaction involved in induction of the mouse IgG2ab suppression is restricted by major histocompatibility complex class I, but not class II molecules.

To determine the major histocompatibility complex (MHC) restriction of the T/ B cell interaction involved in a negative regulation of Ig production, we used mouse model of T cell-induced IgG2ab suppression in vivo. Normal or specifically triggered T splenocytes from mice of the Igha haplotype, when neonatally transferred into histocompatible Igha/b heterozygotes, are able to induce a specific and total suppression of the IgG2ab allotype. Nevertheless, only transfer of IgG2ab-primed Igha T splenocytes induces this suppression in Ighb/b homozygous congenic mice in which the whole IgG2a isotype production is inhibited. This suppression is chronically maintained by CD8+ T cells, but can be experimentally reversed. We have established that the suppression induction required a CD4+CD8+ T cell cooperation and operated via the recognition by the involved TCR of C gamma 2ab-derived peptides presented by the target B cells in an MHC haplotype-restricted manner. Here, by using Ighb mice genetically deficient for MHC class I (beta 2-microglobulin%, or beta 2m%) or class II (I-A beta%) molecules, we demonstrate functionally that the suppression induction implicates an MHC class I-, but not class II-restricted interaction. Indeed, the anti-IgG2ab T cells transferred into Ighb H-2b I-A beta% mice carry out the suppression process normally, while in Ighb H-2b beta 2m% recipients, their suppression induction capacity is significantly inhibited. Moreover, the C gamma 2ab 103-118 peptide, identified as the sole C gamma 2ab-derived peptide able to amplify the anti-IgG2ab T cell reactivity in Igha H-2b mice, is also able to stabilize the H-2Db, but not the H-2Kb class I molecules at the surface of RMA-S (TAP2-, H-2b) cells. These results indicate that, despite the CD4+/CD8+ T cell cooperation during the induction phase of suppression only MHC class I molecule expression is required at the surface of IgG2ab+ B cells for suppression establishment.

Adoptive Transfer↗

PubMed1994

Systemic immune response to peripheral nerve transplants across major histocompatibility class-I and class-II barriers.

The use of peripheral nerve transplantation in limb reconstruction has been limited by tissue rejection. In order to identify the major histocompatibility antigens involved in tissue rejection, mutant strains of inbred mice, differing from the parent strain (C57BL/6) by either major histocompatibility complex Class I (B6.C-H2bml mice) or Class II (B6.C-H2bml2 mice), were used in models of nerve transplantation. One, 2, and 3 weeks after nerve or skin transplantation, the immune response in the recipient animal was monitored with use of lymphocyte-dependent cytotoxicity and complement-dependent cytotoxicity assays. Skin transplants were used for comparison as the gold standard of a nonvascularized graft with an easily observable success or failure. There was no significant cellular immune response by the lymphocyte-mediated cytotoxicity assay when nerve or skin transplants involved an isolated Class-I or Class-II mismatch, but there was a significant response 2 weeks after transplantations across a combined Class-I and Class-II barrier for nerve (p < 0.04) or skin (p < 0.03). An antibody response to the grafts occurred for both skin and nerve transplants but only when a combined barrier was involved. This preliminary study, using a mouse model, suggests that nerve transplantation-may be performed without systemic evidence of rejection with only a partial cross match of the major histocompatibility complexes, thus decreasing the complexity of tissue typing necessary for tissue banking.

Animals↗

PubMed2002

Evidence that the separation of Mhc class II from class I loci in the zebrafish, Danio rerio, occurred by translocation.

In the zebrafish, Danio rerio, and other teleosts, the class I and class II loci of the major histocompatibility complex ( Mhc) reside on different chromosomes. To shed light on the events that might have generated this difference from tetrapods, in which these two types of loci are clustered in a single chromosomal region, the organization of the class II loci in linkage group 8 of the zebrafish was determined by the characterization of contigs of PAC clones. Three contigs were defined: DAB, DCB, and DBB. The 350-kb-long DAB contig contained only four genes: DDB, DAB, SLC7A4, and DAA. The 150-kb-long DCB contig contained the DCB, DCA, and fz10 genes at an undetermined distance from the DAB contig. And the 120-kb-long DBB contig comprised the DBB gene presumably in another linkage group. The low gene density of the linkage group 8 contigs, contrasting with the high gene density of the zebrafish class I region, and the close association with genes [ SLC7A4 coding for an amino acid transporter, and fz10 (frizzled 10) coding for a receptor of the WNT glycoprotein] that are not linked with the tetrapod Mhc, is interpreted to mean that the separation of the class II from class I loci in teleosts occurred by translocation rather than by genomic or chromosomal duplication.

Amino Acid Sequence↗

PubMed2003

MHC polymorphism and disease resistance in Atlantic salmon (Salmo salar); facing pathogens with single expressed major histocompatibility class I and class II loci.

Few studies have yet addressed the functional aspects of MHC molecules in fish. To lay the foundation for this, we evaluated the association between disease resistance and MHC class I and class II polymorphism in Atlantic salmon. Standardized disease challenge trials were performed on a semi-wild Atlantic salmon population with subsequent MHC typing and statistical analysis. The pathogens employed were infectious salmon anaemia virus (ISAV) causing infectious salmon anaemia and the Aeromonas salmonicida bacteria causing furunculosis. The material consisted of 1,182 Atlantic salmon from 33 families challenged with A. salmonicida and 1,031 Atlantic salmon from 25 families challenged with ISAV. We found highly significant associations between resistance towards infectious diseases caused by both pathogens and MH class I and class II polymorphism in Atlantic salmon. The observed associations were detected due to independently segregating MH class I and class II single loci, and inclusion of a large number of fish allowing an extensive statistical analysis.

Aeromonas↗

PubMed1992

Pretransplant sensitization with major histocompatibility complex class I+ class II- hepatocytes leads to accelerated skin graft rejection.

The immunogenicity of major histocompatibility complex (MHC) class I+ class II- hepatocytes is controversial. We studied the effect of pretransplant donor-specific sensitization with either purified hepatocytes (HC) or splenocytes (Spl) on subsequent skin allograft survival. Five million Percoll-purified DBA HC or 10 x 10(6) DBA Spl were injected into C57BL/6 recipients either intraperitoneally (ip) or into a sponge matrix allograft. Twelve days later, sensitized mice received a DBA skin graft. On the same day, allogeneic (DBA) and syngeneic (BL/6) skin grafts were placed on naive BL/6 mice. In naive BL/6 mice, allogeneic skin graft survival was 7.8 +/- 0.5 days (n = 4), and syngeneic survival was indefinite (n = 5). Skin graft survival (mean +/- SD in days) in recipients sensitized with hepatocytes ip was 6.0 +/- 1.2 days (n = 5) compared with 5.6 +/- 0.5 days in recipients sensitized with splenocytes ip. Similarly, graft survival in recipients that received hepatocytes into a sponge matrix allograft was 5.67 +/- 1 days (n = 6) compared with 5.2 +/- 1.1 days (n = 8) in those that received splenocytes into the sponge. There was no difference in graft survival between mice sensitized with HC vs Spl, nor between mice injected ip vs with the sponge. All sensitized mice experienced accelerated graft rejection compared with naive controls (P less than 0.000). These results demonstrate that purified MHC class I+, class II- murine HCs are immunogenic in vivo. Sensitization with donor-specific HCs led to accelerated rejection of subsequent skin grafts, similar to the accelerated rejection seen after sensitization with MHC class I+ and class II+ splenocytes.

Animals↗

PubMed1992

Mycobacterium leprae 65hsp antigen expressed from a retroviral vector in a macrophage cell line is presented to T cells in association with MHC class II in addition to MHC class I.

Mycobacterium leprae lives free in the cytoplasm in infected macrophages. To test if an M. leprae antigen released into the cytoplasm would associate with major histocompatibility complex (MHC) class II we introduced the gene encoding the 65 kDa heat-shock protein (ML65hsp) into a retroviral shuttle vector (pZIPNeoSV(X)) and transfected the murine macrophage cell line J774G8. S1 nuclease mapping and Western blot analysis of the transfected cell line (CJ11) showed that specific messenger RNA and ML65hsp antigen were stably expressed. Presence of antigen at the cell surface was demonstrated by flow cytometric analysis with specific monoclonal antibodies (mAb). Antigen-specific T lymphocytes were stimulated by CJ11 cells to proliferate and release interleukins (IL-2 and IL-3). These responses were blocked by mAbs specific for either MHC class II or for the mycobacterial antigen. The endogenous antigen was also recognised by MHC class I-dependent cytotoxic T cells; cytotoxicity was inhibited by mAbs against either MHC class I molecules or ML65hsp. Thus, production of ML65hsp within the host cytoplasm resulted in association of the antigen with both MHC class I and MHC class II antigen-presenting structures and evoked both lymphocyte proliferation and cytotoxicity towards the antigen-presenting cell. These findings may be relevant to the development of recombinant subunit vaccines against intracellular pathogens.

3T3 Cells↗

PubMed2003

Sequence variability analysis of human class I and class II MHC molecules: functional and structural correlates of amino acid polymorphisms.

Major histocompatibility complex class I (MHCI) and class II (MHCII) molecules display peptides on antigen-presenting cell surfaces for subsequent T-cell recognition. Within the human population, allelic variation among the classical MHCI and II gene products is the basis for differential peptide binding, thymic repertoire bias and allograft rejection. While available 3D structural analysis suggests that polymorphisms are found primarily within the peptide-binding site, a broader informatic approach pinpointing functional polymorphisms relevant for immune recognition is currently lacking. To this end, we have now analyzed known human class I (774) and class II (485) alleles at each amino acid position using a variability metric (V). Polymorphisms (V>1) have been identified in residues that contact the peptide and/or T-cell receptor (TCR). Using sequence logos to investigate TCR contact sites on HLA molecules, we have identified conserved MHCI residues distinct from those of conserved MHCII residues. In addition, specific class II (HLA-DP, -DQ, -DR) and class I (HLA-A, -B, -C) contacts for TCR binding are revealed. We discuss these findings in the context of TCR restriction and alloreactivity.

Alleles↗

PubMed1998

Inhibition of MHC class I and class II cell surface expression on bovine endothelial cells upon infection with Cowdria ruminantium.

Endothelial cells constitute a main target for Cowdria ruminantium (CR) and can potentially play a role as antigen presenting cells (APC). Therefore, we measured, in vitro, the effect of CR infections on the expression of MHC class I and class II molecules on bovine umbilical endothelial cells (BUEC) and on bovine brain endothelial cells (BBEC). A dramatic inhibition of the expression of IFNgamma induced MHC class II molecules was observed on BUEC and to a lesser extent on BBEC upon CR infection. This inhibitory effect was also observed on constitutively expressed MHC class I molecules. Part of the reduction of cell surface MHC molecules could be ascribed to their accumulation in intracellular compartments pinpointing a disruption in the transit of these molecules to the surface of the cells. The exact mechanisms of inhibition are not yet known but, as opposed to what is described in other models, the involvement of prostaglandin E2 can be excluded. The results obtained in this study show that endothelial cells have a decreased capacity to express both MHC class I and class II molecules on their surface upon CR infection, thus favouring the escape of this pathogen from the host immune system.

Animals↗

PubMed1998

Determination of Class II and Class III skeletal patterns: receiver operating characteristic (ROC) analysis on various cephalometric measurements.

Receiver operating characteristic analysis is an excellent method for evaluating and comparing the performance of diagnostic tests. The purpose of this study was to use the receiver operating characteristic analysis to evaluate the diagnostic ability of several cephalometric measurements in determining the presence of Class II and Class III skeletal patterns. Receiver operating characteristic analysis was performed on 976 cases. Fifteen cephalometric measurements were evaluated. A computer software program ROC ANALYZER was used to tabulate the areas under the curves and to perform the statistical comparison between the curves. The results of this study indicated that the Anteroposterior Dysplasia Indicator had the best diagnostic ability in identifying cases with Class II and Class III skeletal patterns. WITS Appraisal and Overjet were highly effective in diagnosing cases with Class II skeletal pattern. WITS Appraisal, Convexity, AB Plane Angle and Overjet also performed well in diagnosing cases with Class III skeletal pattern.

Adolescent↗

PubMed1996

Mice lacking the MHC class II transactivator (CIITA) show tissue-specific impairment of MHC class II expression.

CIITA activates the expression of multiple genes involved in antigen presentation and it is believed to be required for both constitutive and IFN gamma-inducible expression of these genes. To understand the role of CIITA in vivo, we have used gene targeting to generate mice that lack CIITA. CIITA-deficient (-/-) mice do not express conventional MHC class II molecules on the surface of splenic B cells and dendritic cells. In addition, macrophages resident in the peritoneal cavity do not express MHC class II molecules upon IFN gamma stimulation nor do somatic tissues of mice injected with IFN gamma, in contrast with wild-type mice. The levels of Ii and H-2M gene transcripts are substantially decreased but absent in CIITA (-/-) mice. The transcription of nonconventional MHC class II genes is, however not affected by CIITA deficiency. A subset of thymic epithelial cells express MHC class II molecules. Nonetheless, very few mature CD4 T cells are present in the periphery of CIITA (-/-) mice despite MHC class II expression in the thymus. Consequently, CIITA(-/-) mice are impaired in T-dependent antigen responses and MHC class II-mediated allogeneic responses.

Animals↗

PubMed1994

Two Mhc class I and two Mhc class II genes map to the chicken Rfp-Y system outside the B complex.

Gene sequences highly similar to major histocompatibility complex (Mhc) class I and class II genes were recently recognized as mapping to a site in the genome of the chicken separate from the Mhc class I, class II, and B-G genes of the major histocompatibility (B) complex. The present study was undertaken to see whether this complex of Mhc-like genes designated as restriction fragment pattern Y (Rfp-Y) might reside in one of three clusters of cosmid clones contained within the molecular map of chicken Mhc genes, since only two of the three clusters can be assigned to the B system. To determine whether the third cluster (cluster II/IV) might contain Rfp-Y, a subclone (18.1) from within cluster II/IV near a polymorphic lectin gene was used to analyze the DNA of families in which Rfp-Y haplotypes are known to be segregating. The restriction fragment polymorphisms revealed by the 18.1 probe were found to segregate in parallel with the restriction fragment polymorphisms defining the Rfp-Y haplotypes, thus establishing the location of Rfp-Y within cosmid cluster II/IV. Two of six Mhc class I genes and two of five Mhc class II genes map to cosmid cluster II/IV, so a substantial fraction of chicken Mhc genes, including at least one that may be expressed, are located in a chromosomal region separate from the B system. In further linkage analyses, Rfp-Y was found to assort independently from more than 400 markers in the present linkage map of the chicken genome.

Alleles↗

PubMed2003

Expression of HLA class I, beta(2)-microglobulin and HLA class II antigens in primary orbital melanoma.

Major histocompatibility antigens (MHC) play a crucial role in the recognition of tumor cells by the immune system. There is not much information on the role of MHC molecule expression in primary orbital melanomas. In the present study, the authors examined the expression of human leukocyte antigen (HLA) class I, beta(2)-microglobulin (beta(2)-m) and HLA class II antigens in primary orbital melanoma and correlated this with the clinical and pathological findings. HLA class I antigen, beta(2)-m and HLA class II antigen expression were evaluated immunohistochemically in three primary orbital melanomas and correlated with cell type and metastasis. Immunohistochemistry showed heterogeneous expression of HLA class I, beta(2)-m and HLA class II antigen in two cases with no liver metastasis and negative expression in one case with liver metastasis. This preliminary observation deserves further investigation, which may shed more light on the immune escape mechanisms of this tumor and thus make possible novel therapeutic strategies.

Female↗

PubMed2004

HLA class I and class II genotyping in patients with Behcet's disease: a regional study of eastern part of Turkey.

Class I human leucocyte antigen (HLA)-B51 is well known to be associated with Behcet's disease in many ethnic groups. However, there has been no published paper with respect to its association with HLA class I and class II among the Turkish people who live in the eastern region of Turkey. Moreover, as it is known that B51 antigen is encoded by 21 alleles, B*5101-5121, HLA-B51 allele typing was performed, as well as HLA class I and class II genotyping of 75 patients with the disease and the 54 individuals in the matched control group. The result shows that the HLA-B51 frequency was significantly higher (58.66%) in the patient group, compared to that in the control group (18.51%) (OR = 6.245). In the subtyping of B51 alleles, 44 B51-positive patients possessed B*5101 (45.5%), B*5108 (25%), B*5105 (9.1%) and B*5104 (4.5%). There was no significant difference in the HLA-B51 allelic distribution between the patient group and the control group. However, homozygous carriers of HLA-B51 showed considerably high risk (OR = 2.647) in the patient group, compared to that in the control group. In the genotyping of class II HLA alleles, while HLA-DRB1*04 (45.3%) and HLA-DRB1*07 (24%) were the predominant alleles in the patient group, DRB1*11 (50%) appeared to be more common in the control group.

Behcet Syndrome↗