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At least 703 records · Page 39Linked to original sources
PubMed2003

MHC restriction in allergic bronchopulmonary aspergillosis.

Allergic bronchopulmonary aspergillosis (ABPA) is a rare complication in patients with asthma but more common in patients with cystic fibrosis. In the presence of the fungus Aspergillus fumigatus (Af) in the lower respiratory tract, patients mount a heightened IgG and IgE humoral response specific for Af antigens. Studies on ABPA have suggested a pathogenic role for antigen specific CD4+ Th2 like T lymphocytes producing increased levels of IL-4 and IL-5. MHC class II genes coding for highly polymorphic HLA molecules have been shown to be the likely candidates for controlling immune responses to common allergens. However there has been a lack of information on the pathophysiological role of HLA genes in the development of ABPA. This review describes an association between HLA- class II alleles and the specific responses to Af antigen (Asp f 1) in ABPA. These studies focused on MHC restriction and distribution of HLA- class II alleles in two groups of unrelated North American Caucasian patients with cystic fibrosis and/or asthma. One group consisted of patients with a confirmed diagnosis of ABPA and a second group of patients with Af sensitivity but no ABPA. HLA association studies revealed that the predisposition to develop ABPA is associated with HLA-DR2 and DR5, and possibly DR4 or DR7. A strong association of HLA-DR antigens with ABPA reflects that HLA-DR molecules may present disease-causing peptides. On the other hand a significant association of HLA-DQ2 with Af sensitive nonABPA indicates the involvement of HLA-DQ molecules in protection. A combination of these genetic factors determines the outcome of ABPA in patients with cystic fibrosis and asthma.

Animals↗
PubMed2000

Enhanced susceptibility to lupus contributed from the nonautoimmune C57BL/10, but not C57BL/6, genome.

Genes from New Zealand Black and New Zealand White mice have been implicated in the development of a disease similar to human systemic lupus erythematosus. In an attempt to define the MHC class II genes involved in disease, we previously studied similarly designed backcrosses of New Zealand Black mice with C57BL/6 (B6) mice transgenic for Ez genes or with C57BL/10 (B10) mice transgenic for Az genes. Although the transgenes showed no effect on the development of autoantibody production or lupus nephritis in either backcross, surprisingly, there was greatly increased expression of these disease traits in the backcrosses involving B10 compared with B6 mice. These studies therefore implicated genetic contributions in B10 vs B6 backgrounds, despite their 98% identity. A genome-wide linkage analysis uncovered a B10 locus on mid-chromosome 13, which enhanced nephritis and was strongly linked with the production of pathogenic retroviral gp70-anti-gp70 immune complexes when contributed by B10, but not B6, mice. The subsequent identification of a single marker polymorphic between B10 and B6, along with the extreme genetic similarity between the two strains in this region, is likely to permit expedited identification of the lupus-susceptibility gene from this nonautoimmune strain.

Animals↗
PubMed2000

Dendritic cells permit identification of genes encoding MHC class II-restricted epitopes of transplantation antigens.

Minor or histocompatibility (H) antigens are recognized by CD4+ and CD8+ T lymphocytes as short polymorphic peptides associated with MHC molecules. They are the targets of graft versus host and graft versus leukemia responses following bone marrow transplantation between HLA-identical siblings. Several genes encoding class I-restricted minor H epitopes have been identified, but approaches used for these have proved difficult to adapt for cloning class II-restricted minor H genes. We have combined the unique antigen-presenting properties of dendritic cells and high levels of episomal expression following transfection of COS cells to identify a Y chromosome gene encoding two HY peptide epitopes, HYAb and HYEk.

Amino Acid Sequence↗
PubMed2004

Low diversity in the major histocompatibility complex class II DRB1 gene of the Spanish ibex, Capra pyrenaica.

During the last two centuries, the Spanish ibex (Capra pyrenaica) has shown a significant demographic decline as a result of the progressive destruction of its natural habitat, disease epidemics, and uncontrolled hunting. Partial sequencing of the class II MHC DRB1 gene revealed that the Spanish ibex has remarkably low levels of genetic variation at this locus, with only six different DRB1 alleles and an observed heterozygosity of 0.429-0.579. The rates of nonsynonymous vs synonymous substitutions were significantly different in the peptide-binding region (dN/dS=5.347, P=0.002), a feature that indicates that the DRB1 gene is under positive selection. A phylogenetic analysis of the Spanish ibex and a set of domestic goat DRB1 alleles revealed that the reported sequences represent four major allelic lineages. The limited allelic repertoire of the DRB1 gene in the Spanish ibex is likely the direct result of the recent history of population bottlenecks and marked demographic decline of this species. A genetic survey of 13 microsatellite loci was consistent with this idea. The Spanish ibex subspecies C. p. hispanica and C. p. victoriae consistently showed considerably lower levels of microsatellite heterozygosity (Ho=0.184-0.231) and allelic diversity (mean number of alleles per locus=2-2.4) than those reported in other wild ruminants. This study demonstrates the significance of both natural selection and the demographic history of populations in determining patterns of genetic variation at MHC loci. In addition, our results emphasize the importance of locally adapted populations for the preservation of genetic diversity.

Amino Acid Sequence↗
PubMed1988

Detection and regulation of rat thyroid MHC class II (RT1.D) transcripts.

We have reexamined 1B-6 cells, a cloned line of FRTL-5 rat thyroid cells in order to determine whether such cells demonstrate constitutive MHC class II gene expression. A new homologous cDNA probe for the RT1.D alpha-chain region was developed and proved significantly more sensitive at detecting specific mRNA levels in 1B-6 cells than a human class II alpha-chain specific probe used in previous studies. Recombinant rat gamma-interferon induced MHC class II (RT1.D) antigen at concentrations as low as 1 U/ml (in the presence of bovine TSH), as detected by both alpha-chain specific mRNA transcripts and surface antigen expression. There was no evidence for constitutive expression of MHC class II transcripts in proliferating 1B-6 cells in the absence of gamma-interferon, even when bovine TSH was present. These studies add further evidence to our hypothesis that MHC class II antigen expression in thyroid cells is secondary to external stimulating factors.

Animals↗
PubMed1999

Targeted disruption of CRE-binding factor TREB5 gene leads to cellular necrosis in cardiac myocytes at the embryonic stage.

TREB5 (hXBP-1) is a basic region leucine zipper protein which binds to a CRE-like element in both human T-cell leukemia virus type 1 and MHC class II genes. To study the function(s) of TREB5 in normal development, we have generated TREB5 deficient mice by gene targeting. Heterozygous mutant mice have not exhibited any obvious abnormalities; however, homozygous mutant embryos die between embryonic days 10.5 and 14.5. The major defect responsible for lethality is cellular necrosis of cardiac myocytes located at the atrium and the truncus arteriosus with its following ventricle. Necrotic alteration was not observed in either the endocardial cushion or the conotruncal ridge. These results indicate that TREB5 plays an essential role in maintenance and/or growth of cardiac myocytes during cardiogenesis.

Animals↗
PubMed1992

Conservation of the HLA-DQB2 locus in nonhuman primates.

The evolutionary history of MHC class II genes is characterized by several examples of gene duplication, leading both to the creation of distinct subregions such as DR, DQ, and DP, as well as to duplicated loci within each of these subregions. In the human MHC, a prominent example of this diversification occurs within the HLA-DQ subregion, where the nonpolymorphic and transcriptionally "silent" DQB2 locus is highly homologous to the polymorphic expressed DQB1 locus. In order to gain some insight into the mechanisms constraining polymorphism at the DQB2 locus, the second exons of five nonhuman primate DQB2 alleles were sequenced. Six nonhuman primate DQB2 analogous sequences were obtained, two each from chimpanzee and owl monkey cell lines, and one each from gorilla and gibbon cell lines. Notably, the DQB2 sequences from the gibbon, gorilla, and one of the two chimpanzee sequences, although containing some silent nucleotide changes, encode a predicted DQB2 protein with 100% homology to the human DQB2 sequence. The owl monkey DQB2 allelic sequences and the other chimpanzee DQB2 sequence contain additional polymorphisms, but maintain approximately 95% nucleotide sequence identity with human and the other primate sequences. Identification of the owl monkey DQB2 locus indicates that the ancestral DQ gene duplication event occurred at least 40 million years ago, rather than 10 million years, as previously thought. Remarkably, nucleotide sequences from amplified cDNA indicate that the DQB2 gene, and not the DQB1 gene, may be transcribed in the owl monkey line. Substitutions occur at sites comparable to codons of well-recognized allelic variation in the functional DQB1 genes, implying that variation within the DQB2 locus operates under similar selection constraints to the DQB1 locus, with an extremely high degree of conservation through primate evolution.

Animals↗
PubMed1999

Major histocompatibility complex (MHC) class II polymorphism and paternity in the monogamous Hypogeomys antimena, the endangered, largest endemic Malagasy rodent.

Sequence variation at a major histocompatibility complex (MHC) class II gene was examined in Hypogeomys antimena, a monogamous endemic rodent of Madagascar. The study was conducted throughout its remaining geographical range (20 x 40 km) by direct sequencing and single-strand conformation polymorphism (SSCP). The objectives of the study were: (i) to investigate levels of polymorphism in the MHC complex of a highly endangered species that experienced a severe reduction in population size; and (ii) to investigate the genetic mating system by assessing the frequency of extra-pair paternity (EPP) as EPP might have important consequences to increase gene flow and, therefore, genetic variability within a population. The amplified gene segment had a very low variability (only two alleles) in H. antimena compared with other mammalian species. The alleles segregated consistently with Mendelian expectations in families. No case of EPP was found. The present data suggest no difference between the social and the genetic mating system.

Animals↗
PubMed1994

A synthetic peptide from the third hypervariable region of major histocompatibility complex class II beta chain as a vaccine for treatment of experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is a class II major histocompatibility complex (MHC)-restricted, T-cell-mediated, demyelinating autoimmune disease of the central nervous system and represents a model for human multiple sclerosis. The present study demonstrates that vaccination of SJL/J mice with an 18-amino acid synthetic peptide from the third hypervariable region of the murine class II MHC IAs beta chain (IAs beta 58-75; 18-mer peptide) is capable of eliciting auto-anti-IAs antibodies specific for the IAs beta chain and preventing and treating EAE. A similar approach may be useful in the treatment of human autoimmune diseases in which susceptibility is linked to class II MHC genes.

Amino Acid Sequence↗
PubMed1991

Effects of TNF alpha on the expression of class II MHC molecules in macrophages induced by IFN gamma: evidence for suppression at the level of transcription.

Tumor necrosis factor-alpha (TNF-alpha) induces surface expression of class II major histocompatibility (MHC) molecules (la molecules) in many cells, including macrophage-like cell lines. When we tested the effects of this cytokine on murine peritoneal macrophages, TNF alpha had little effect on surface expression of la. The strong expression of such molecules induced by interferon-gamma (IFN gamma) was, however, suppressed moderately by TNF alpha. These effects were reflected at the level of specific messenger RNA (mRNA) as detected by Northern blot analysis. Furthermore, the locus of control appears to be transcriptional; in nuclear run-on assays, TNF alpha suppressed the IFN gamma-induced enhancement of transcription for the murine beta-chain of I-A (I-A beta.). Taken together the data suggest that TNF alpha has little effect on class II MHC genes and surface expression in murine peritoneal macrophages, that TNF alpha is a modest suppressant of such molecules when their levels are raised by IFN gamma, and that these suppressive effects are mediated at the level of transcription.

Animals↗
PubMed1996

Genomic organization of a mouse MHC class II region including the H2-M and Lmp2 loci.

The region encompassing the Ma, Mb1, Mb2, and Lmp2 genes of the mouse class II major histocompatibility complex (MHC) was sequenced. Since this region contains clusters of genes required for efficient class I and class II antigen presentation, it was interesting to search for putative additional genes in the 21 kilobase gap between the Mb1 and Lmp2 genes. Computer predictions of coding regions and CpG islands, exon trapping experiments, and cross-species comparison with the corresponding human sequence indicate that no additional functional gene is present in that stretch. However, computer analysis revealed the possible existence of an alternative 3' exon for Mb1. Except for the fact that the mouse MHC contains two Mb genes, the genomic organization of the H2-M loci was found to be almost identical to the organization of the human HLA-DM genes. The promoter regions of the Ma and Mb genes also resemble classical class II promoters, containing typical S, X, and Y boxes. Like the human genes, the three H2-M genes displayed very limited polymorphism when we compared the cDNA sequences from six haplotypes. Finally, comparison of DMB with Mb1 and Mb2, both at the genomic level and in their coding regions, suggests that the Mb gene was recently duplicated, probably only in certain rodents.

Animals↗
PubMed1986

In vitro allostimulation of peripheral blood mononuclear cells generates autologous reactive T lymphocytes: analysis at the clonal level.

Cells from two siblings within family PER with a maternal crossing-over were used as responder and stimulator cells; they differed in class II MHC gene products. The responder cells were cloned and studied for their specificity. All the clones were T4+, most of them, were allospecific cytotoxic T-cell clones, some were only proliferative. Among the 62 clones that have been screened for their phenotype and function, we could expand, in our cloning system, two autoreactive T-cell clones specific for the self-class II MHC products. The results indicated that this autoreactivity was also observed in serum-free medium, which excludes any serum components susceptible to alter the self-class II MHC products. For the autorecognition, the two clones used the T3-Ti complex, and only one of them, the T4 structure.

Antibodies, Monoclonal↗
PubMed1992

The antigen-processing mutant T2 suggests a role for MHC-linked genes in class II antigen presentation.

.174xCEM.T2 (T2) is a human cell hybrid that has a large homozygous deletion within the MHC, including all of the functional class II genes. We have generated stable HLA-DR3 and H-2 I-Ak transfectants of T2 that express parental levels of class II molecules at the cell surface. T2.Ak transfectants fail to stimulate a hen egg lysozyme (HEL)-specific, I-Ak-restricted T cell when incubated with intact HEL. However, stimulation occurs if the appropriate HEL peptide is provided. The T2 cell line therefore has a defect in class II-restricted Ag processing. Biosynthetic studies demonstrate that the kinetics of I-Ak transport in T2.Ak are similar to the parental rates of transport, although the percentage of I-Ak molecules transported appears somewhat lower. I-Ak glycoproteins in T2.Ak associate normally with the I-chain, which appears to be proteolytically cleaved after transport through the Golgi apparatus in a similar fashion to that in the parent cell line, .174xCEM.T1 (T1). The DR alpha beta heterodimers in T2 differ from the parental phenotype in two ways. First, HLA-DR3 expressed in T2 does not have the epitope recognized by the DR3-specific mAb 16.23, although DR3 expressed in the parent does have the epitope. Second, the alpha beta subunits in the parent remain associated when exposed to SDS at room temperature, although those in T2 dissociate.

Epitopes↗
PubMed1987

Analysis of restriction fragment length polymorphisms in rheumatic diseases.

Considerable evidence indicates that genes residing within the major histocompatibility complex (MHC) influence susceptibility to certain rheumatic diseases, such as ankylosing spondylitis (AS) and rheumatoid arthritis (RA). However, it has not yet been possible to precisely identify the gene(s) responsible for conferring enhanced susceptibility to these diseases. The availability of recombinant DNA technology should accelerate progress in obtaining this goal. A particularly promising method in this regard is restriction fragment length polymorphism (RFLP) analysis using appropriate class I and class II MHC gene probes. In preliminary studies, RFLPs have been identified for AS and RA which associate with susceptibility to the disease. Further studies using this approach should permit localization and precise identification of the disease susceptibility gene(s) for these diseases.

Arthritis, Rheumatoid↗
PubMed1990

Characterization of the adjuvant-free serological response to protein antigens coupled to antibodies specific for class II MHC determinants.

Having previously demonstrated that coupling protein antigens to anti-class II major histocompatibility complex (MHC) monoclonal antibodies provides a means of inducing adjuvant-independent IgG responses to the 'targeted' antigen, we have now explored the parameters of this response in more detail. Using as the model system egg avidin coupled to biotinylated anti-class II MHC mAbs, the kinetics of the avidin-specific 1 degrees IgG response, the IgG subclass distribution of the 2 degrees anti-avidin response, and the immunogenicity of anti-class II-avidin conjugates in H-2-recombinant mice have been investigated. In addition, the use of avidin as a bridging molecule in the creation of immunoconjugates involving third-party proteins has been further characterized, and the immunogenicity of defined soluble conjugates in mice bearing the appropriate class II MHC gene products has been demonstrated. These findings extend our understanding of the immunoconjugate approach to adjuvant-independent immunization, and support its exploration as an alternative means of subunit vaccine design.

Animals↗
PubMed2002

Differential splicing generates Tvl-1/RFXANK isoforms with different functions.

Earlier studies have shown that Tvl-1 gives rise to at least two differentially spliced mRNAs, one of which (Tvl-S) encodes a protein that lacks amino acids 91-112. DNA binding of RFX complexes assembled in the presence of Tvl-S is impaired. As a result, Tvl-S does not support the expression of Class II major histocompatibility complex (MHC) genes. Here, we show that the reason Tvl-S is inactive as a transcriptional regulator of Class II MHC genes is that the RFX complexes assembled in the presence of Tvl-S are unstable. Additionally, we show that interferon-gamma, which induces Class II MHC gene expression in 293 cells, promotes a shift in the splicing pattern of RFXANK/Tvl-1 toward the transcriptionally active Tvl-L isoform, suggesting that differential splicing of Tvl-1 is a signal-regulated process. Finally, we show that Tvl-1 regulates the expression of non-MHC genes. One such gene encodes the ephrin receptor EphA3. Since both Tvl-L and Tvl-S are identical in their ability to induce the expression of EphA3, we conclude that Tvl-1 regulates the expression of non-MHC genes by RFX-independent mechanisms.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Nucleotide sequence of the ring3 gene in the class II region of the mouse MHC and its abundant expression in testicular germ cells.

The RING3 (NAT) gene is the first and only locus with no obvious function associated with the immune system in the class II region of the human major histocompatibility complex. This gene is a homologue of the Drosophila homeotic gene female sterile homeotic (fsh) and encodes a nuclear serine-threonine kinase. To study more about the physiological function of the RING3 gene, we isolated a mouse homologue from a genomic library, determined its gene structure, and investigated its expression profile. The mouse Ring3 gene spans approximately 8 kb and consists of 12 exons encoding a 798-amino-acid protein, sharing as high as 96% amino acid identity with the human RING3 protein. Northern hybridization revealed that the Ring3 gene abundantly produced 3.8- and 3.0-kb transcripts in the testis but was weakly expressed with 4.6- and 3.8-kb transcripts in somatic tissues. It appears that testis-specific 3.0-kb transcript gives rise to a smaller size Ring3 protein resulting from the usage of the second ATG codon for translational initiation compared to the almost ubiquitous 4.6-kb transcript. In RNAs isolated from fractionated testicular germ cells, the two testicular mRNAs were detected exclusively in the fractions containing a large population of round spermatids and pachytene spermatocytes. Furthermore, in situ hybridization on cross sections of seminiferous tubules in the testis showed that the expression of the Ring3 gene was initiated at the pachytene spermatocyte stage during meiosis and persisted throughout the round spermatid stage during spermiogenesis. These results suggest that the Ring3 gene plays an important role in spermatogenesis.

Amino Acid Sequence↗
PubMed1992

A homologue of the Drosophila female sterile homeotic (fsh) gene in the class II region of the human MHC.

The RING3 gene maps in the class II region of the human major histocompatibility complex, at a CpG island distal of the HLA-DNA gene. RING3 cDNAs were obtained from a T cell cDNA library and the longest (4 kb) was sequenced. The sequence contained an open reading frame encoding a protein of 754 amino acids. A screen of protein databases revealed striking homology between the RING3 protein and the Drosophila female sterile homeotic gene (fsh) which is implicated in the establishment of segments in the early embryo. Partial sequence homology was also observed with some other proteins involved in cell cycle control (CCG1), cell division (ftsA) and regulation of cell growth (gamma interferons). This highly conserved gene may play an important role in human development. In addition, its location in the MHC class II region may be related to some HLA-associated diseases.

Amino Acid Sequence↗