Major Histocompatibilty Complex Class Research Articles

MON-190 MICA - A MYTH TO REALITY IN CLINICAL PRACTICE

THE MAJOR HISTOCOMPATIBILTY COMPLEX CLASS 1 RELATED CHAIN – is the product of an HLA-related polymorphic gene and is expressed on monocytes keratinocytes fibroblast and endothelial cells. In this study we looked at the incidence of MICA Antibodies in the preop evaluation of kidney transplant patients and serum creatinine levels post kidney transplant using a combination of plasma exchange and rATG peritransplant

Characterization of major histocompatibility complex class I loci of the lark sparrow (Chondestes grammacus) and insights into avian MHC evolution.

The major histocompatibilty complex (MHC) has become increasingly important in the study of the immunocapabilities of non-model vertebrates due to its direct involvement in the immune response. The characterization of MHC class I loci in the lark sparrow (Chondestes grammacus) revealed multiple MHC class I loci with elevated genetic diversity at exon 3, evidence of differential selection between the peptide binding region (PBR) and non-PBR, and the presence of multiple pseudogenes with limited divergence. The minimum number of functional MHC class I loci was estimated at four. Sequence analysis revealed d N /d S ratios significantly less than one at non-PBR sites, indicative of negative selection, whereas PBR sites associated with antigen recognition showed ratios greater than 1 but non-significant. GenBank surveys and phylogenetic analyses of previously reported avian MHC class I sequences revealed variable signatures of evolutionary processes acting upon this gene family, including gene duplication and potential concerted evolution. An increase in the number of class I loci across species coincided with an increase in pseudogene prevalence, revealing the importance of gene duplication in the expansion of multigene families and the creation of pseudogenes.

Immunization of mice with lentiviral vectors targeted to MHC class II+ cells is due to preferential transduction of dendritic cells in vivo.

Gene transfer vectors such as lentiviral vectors offer versatile possibilities to express transgenic antigens for vaccination purposes. However, viral vaccines leading to broad transduction and transgene expression in vivo, are undesirable. Therefore, strategies capable of directing gene transfer only to professional antigen-presenting cells would increase the specific activity and safety of genetic vaccines. A lentiviral vector pseudotype specific for murine major histocompatibilty complex class II (LV-MHCII) was recently developed and the present study aims to characterize the in vivo biodistribution profile and immunization potential of this vector in mice. Whereas the systemic administration of a vector pseudotyped with a ubiquitously-interacting envelope led to prominent detection of vector copies in the liver of animals, the injection of an equivalent amount of LV-MHCII resulted in a more specific biodistribution of vector and transgene. Copies of LV-MHCII were found only in secondary lymphoid organs, essentially in CD11c+ dendritic cells expressing the transgene whereas B cells were not efficiently targeted in vivo, contrary to expectations based on in vitro testing. Upon a single injection of LV-MHCII, naive mice mounted specific effector CD4 and CD8 T cell responses against the intracelllular transgene product with the generation of Th1 cytokines, development of in vivo cytotoxic activity and establishment of T cell immune memory. The targeting of dendritic cells by recombinant viral vaccines must therefore be assessed in vivo but this strategy is feasible, effective for immunization and cross-presentation and constitutes a potentially safe alternative to limit off-target gene expression in gene-based vaccination strategies with integrative vectors.

Increased serum interleukin-33 levels in patients with Graves’ disease

Interleukin-33 (IL-33), a 30 kDa cytokine, is a member of IL-1 family. It is considered to be an autoimmune biomarker associated with T helper 2 (Th 2) response. γ-interferon is also produced by T helper 1 (Th 1) cells to induce cellular responses. γ-interferon is a 143-amino acid residue glycoprotein with several biological functions including potent anti-viral activity, stimulation of macrophage activity, modulation of Major Histocompatibilty Complex class I/class II expression, and regulation of a diversity of specific immune responses. The aim of this study was to investigate the serum levels of IL-33 and γ-interferon in different thyroid disorders. Twenty patients with Graves' disease, 21 patients with Hashimoto hypothyroidism, 21 euthyroid Hashimoto patients, and 27 control subjects were recruited to this study. Blood samples were drawn and IL-33 and γ-interferon tests were analyzed from 89 participants. Serum IL-33 and γ-interferon analyses were performed by enzyme-linked immunosorbent assay. There was no statistically significant difference between groups for serum γ-interferon levels. Serum IL-33 concentrations were significantly higher in Graves' disease group compared to the other groups (p<0.000) There was a positive correlation between serum IL-33 and free triiodothyronine (fT3) and thyroxine (fT4). Also, negative correlation between serum IL-33 and thyroid-stimulating hormone (TSH) was statistically significant (p<0.000). The correlation of serum IL-33 with thyroid hormone levels may be a useful indicator for Graves' disease. These findings may help to make evident the pathophysiologic processes of the autoimmune thyroid diseases and improve therapeutic methods. .

Occupancy of whole blood cells by a single PIGA‐mutant clone with HMGA2 amplification in a paroxysmal nocturnal haemoglobinuria patient having blood cells with NKG2D ligands

Occupancy of whole blood cells by a single <i><scp>PIGA</scp></i>‐mutant clone with <i><scp>HMGA</scp>2</i> amplification in a paroxysmal nocturnal haemoglobinuria patient having blood cells with <scp>NKG</scp>2D ligands

IRAK-M modulates expression of IL-10 and cell surface markers CD80 and MHC II after bacterial re-stimulation of tolerized dendritic cells

BackgroundAs essential components of the innate immune system, dendritic cells (DCs) can interact directly with pathogens as well as participate in the adaptive immune response. In cells closely related to DCs such as macrophages and monocytes, prior exposure to minute amounts of endotoxin can lead to a refractory period where subsequent exposure to higher doses fails to induce an inflammatory response; little research has investigated this effect on DCs. This study tested if murine bone marrow-derived dendritic cells (BM-DCs) respond to endotoxin- and bacterial sonicate-induced tolerance by decreased inflammatory and increased anti-inflammatory response, and the role of IRAK-M, an intracellular negative regulator of TLR signaling, in this tolerance. ResultsTolerized BM-DCs exhibited a significant drop in TNF-α and IL-12p70 production and increased IL-10 expression compared to untolerized cells. BM-DCs also showed the ability to develop heterotolerance, in which the LPS exposure alone was able to induce tolerance to Helicobacter pylori sonicate and TLR2 agonist Pam3Cys. Furthermore, the expression of IRAK-M was increased after restimulation of tolerized BM-DCs as determined qPCR and Western blot. IRAK-M exhibited a suppressive effect on surface expression of major histocompatibilty complex class II (MHC II) and CD80 in LPS-tolerized BM-DCs. IL-10 expression in bacterial sonicate-tolerized IRAK-M−/− BM-DCs was altered as compared to wild type BM-DCs, with tolerance-induced expression of IL-10 mitigated in tolerized IRAK-M−/− BM-DCs. ConclusionAlong with endotoxin, bacterial sonicate is able to induce refractory tolerance in BM-DCs, and IRAK-M plays a role in modulating cell surface expression of MHC class II and CD80 and release of IL-10 during this tolerance.

CIITA is silenced by epigenetic mechanisms that prevent the recruitment of transactivating factors in rhabdomyosarcoma cells

Rhabdomyosarcomas (RMS) are highly malignant pediatric sarcomas. We have discovered that the gene encoding the major histocompatibilty complex class II transactivator, CIITA, is silenced in cells representing both major subtypes of RMS. Silencing of CIITA prevents the IFN-γ inducible expression of MHC class II genes in these cells. Overexpression of CIITA in these cells can restore MHC expression. We have found that IFN-γ signaling is intact in these cells, but pSTAT1 and IRF1 do not bind to the CIITA PIV promoter. The CIITA promoter is not hypermethylated in RD (ERMS) cells but does show a modestly enhanced methylation status in SJRH30 (ARMS) cells. We have found that histone acetylation, which normally increases on the CIITA PIV promoter following IFN-γ treatment, is blocked in both types of RMS cells. In RD cells, treatment with a histone deacetylase inhibitor (TSA) reverses the silencing of CIITA. In SJRH30 cells, treatment with DNA methyltransferase inhibitors and TSA cooperatively restores CIITA expression. Surprisingly, we have also shown that the expression of two components of the immunoproteasome, which are embedded in the class II locus, is stimulated by IFN-γ in certain RMS cells in the absence of stimulation by CIITA. CIITA overexpression can also activate the expression of these genes, indicating that the immunoproteasome genes LMP2 and LMP7 can be activated by both CIITA dependent and CIITA independent pathways.

Novel immunomodulatory effects of adiponectin on dendritic cell functions

Adiponectin (ADN) is an adipocytokine with anti-inflammatory properties. Although it has been reported that ADN can inhibit the immunostimulatory function of monocytes and macrophages, little is known of its effect on dendritic cells (DC). Recent data suggest that ADN can regulate immune responses. DCs are uniquely specialised antigen presenting cells that play a central role in the initiation of immunity and tolerance. In this study, we have investigated the immuno- modulatory effects of ADN on DC functions. We found that ADN has only moderate effect on the differentiation of murine bone marrow (BM) derived DCs but altered the phenotype of DCs. The expression of major histocompatibilty complex class II (MHCII), CD80 and CD86 on ADN conditioned DCs (ADN-DCs) was lower than that on untreated cells. The production of IL-12p40 was also suppressed in ADN-DCs. Interestingly, ADN treated DCs showed an increase in the expression of the inhibitory molecule, programmed death-1 ligand (PDL-1) compared to untreated cells. In vitro co-culture of ADN-DCs with allogeneic T cells led to a decrease in T cell proliferation and reduction of IL-2 production. Concomitant with that, a higher percentage of CD4 +CD25 +Foxp3 + regulatory T cells (Tregs) was detected in co-cultures of T cells and ADN-DCs. Blocking PD-1/PDL-1 pathway could partially restore T cell function. These findings suggest that the immunomodulatory effect of ADN on immune responses could be at least partially be mediated by its ability to alter DC function. The PD-1/PDL-1 pathway and the enhancement of Treg expansion are implicated in the immunomodulatory mechanisms.

Roles for common MLL/COMPASS subunits and the 19S proteasome in regulating CIITA pIV and MHC class II gene expression and promoter methylation

BackgroundStudies indicate that the 19S proteasome contributes to chromatin reorganization, independent of the role the proteasome plays in protein degradation. We have previously shown that components of the 19S proteasome are crucial for regulating inducible histone activation events in mammalian cells. The 19S ATPase Sug1 binds to histone-remodeling enzymes, and in the absence of Sug1, a subset of activating epigenetic modifications including histone H3 acetylation, H3 lysine 4 trimethylation and H3 arginine 17 dimethylation are inhibited at cytokine-inducible major histocompatibilty complex (MHC)-II and class II transactivator (CIITA) promoters, implicating Sug1 in events required to initiate mammalian transcription.ResultsOur previous studies indicate that H3 lysine 4 trimethylation at cytokine-inducible MHC-II and CIITA promoters is dependent on proteolytic-independent functions of 19S ATPases. In this report, we show that multiple common subunits of the mixed lineage leukemia (MLL)/complex of proteins associated with Set I (COMPASS) complexes bind to the inducible MHC-II and CIITA promoters; that overexpressing a single common MLL/COMPASS subunit significantly enhances promoter activity and MHC-II HLA-DRA expression; and that these common subunits are important for H3 lysine 4 trimethylation at MHC-II and CIITA promoters. In addition, we show that H3 lysine 27 trimethylation, which is inversely correlated with H3 lysine 4 trimethylation, is significantly elevated in the presence of diminished 19S ATPase Sug1.ConclusionTaken together, these experiments suggest that the 19S proteasome plays a crucial role in the initial reorganization of events enabling the relaxation of the repressive chromatin structure surrounding inducible promoters.

Autoimmune disease association signals in CIITA and KIAA0350 are not involved in celiac disease susceptibility

Celiac disease (CD) is a multifactorial disease characterized by intestinal inflammation after gluten exposure in genetically susceptible individuals. A strong influence of certain human leukocyte antigen (HLA) alleles (those coding the HLA-DQ2 and DQ8 heterodimers) is well established, but they cannot explain the overall genetic risk. CIITA could be a good candidate gene for CD because it is mainly transcriptionally regulated, and it encodes the master regulator of major histocompatibilty complex class II gene transcription. CIITA is located in 16p13, a region also containing KIAA0350 (CLEC16A), associated with two autoimmune diseases in genome-wide association studies. We aimed at studying the involvement of polymorphisms in CIITA and KIAA0350 in CD susceptibility, with special attention to evaluate the possible presence of more than one risk factor in the region. We performed a case-control study with 607 CD patients and up to 794 healthy controls, all Spaniards. All samples were genotyped for five single nucleotide polymorphisms: rs3087456 (-168A/G) and rs4774 in CIITA and rs7203459, rs6498169 and rs2903692 in KIAA0350. No significant results were obtained when comparing genotypic, allelic or haplotypic frequencies between patients and controls. Our results seem to discard the influence in CD susceptibility of CIITA and KIAA0350 markers previously associated with other autoimmune diseases.

Murine neutrophils present Class II restricted antigen

Neutrophils were originally described as short lived, terminally differentiated phagocytes that contribute only to the innate immune response. Recent evidence of neutrophil cytokine production and expression of numerous cell surface proteins has suggested that neutrophils are likely to influence adaptive responses and may satisfy the criteria of antigen presenting cells. Under certain inflammatory conditions human neutrophils express major histocompatibilty complex (MHC) Class II and the costimulatory molecules CD80 and CD86. We have employed a murine T cell hybridoma with a transgenic T cell receptor specific for ovalbumin peptide 323–339 (OVA323–339), and a green fluorescent reporter of T cell receptor ligation, to directly investigate neutrophil-T cell interactions. These cells provide an ideal model system, allowing precise identification of antigen specificity and a clear readout of T cell activation. Additionally, whilst murine neutrophils have previously been shown to stimulate MHC Class I-dependent CD8+ T cell activation, CD4+ T cells stimulation via MHC Class II-expressing neutrophils has not been investigated. We addressed this by isolating murine neutrophils, loading with OVA323–339 and co-culturing with T cells specific for the OVA323–339/MHC Class II complex, and this resulted in T cell activation, as determined by expression of the green-fluorescent protein reporter. Antigen-pulsed neutrophils were also able to prime naïve OVA-specific CD4+ T cells in a contact-dependent manner, as shown by proliferation and cytokine production. Activation of lymphocytes was not due to contaminating macrophages. These studies demonstrate that murine neutrophils present MHC Class II-restricted peptides and induce T cell proliferation, confirming findings in human neutrophils, and demonstrate a novel pro inflammatory effect of murine neutrophils.

Induction of HLA-B27 heavy chain homodimer formation after activation in dendritic cells

IntroductionAnkylosing spondylitis (AS) is a severe, chronic inflammatory arthritis, with a strong association to the human major histocompatibilty complex (MHC) class I allele human leucocyte antigen (HLA) B27. Disulfide-linked HLA-B27 heavy-chain homodimers have been implicated as novel structures involved in the aetiology of AS. We have studied the formation of HLA-B27 heavy-chain homodimers in human dendritic cells, which are key antigen-presenting cells and regulators of mammalian immune responses.MethodBoth an in vitro dendritic-like cell line and monocyte-derived dendritic cells from peripheral blood were studied. The KG-1 dendritic-like cell line was transfected with HLA-B27 cDNA constructs, and the cellular distribution, intracellular assembly and ability of HLA-B27 to form heavy-chain homodimers was compared with human monocyte-derived dendritic cells after stimulation with bacterial lipopolysaccharide (LPS).ResultsImmature KG-1 cells expressing HLA-B27 display an intracellular source of MHC class I heavy-chain homodimers partially overlapping with the Golgi bodies, but not the endoplasmic reticulum, which is lost at cell maturation with phorbyl-12-myristate-13-acetate (PMA) and ionomycin. Significantly, the formation of HLA-B27 homodimers in transfected KG-1 cells is induced by maturation, with a transient induction also seen in LPS-stimulated human monocyte-derived dendritic cells expressing HLA-B27. The weak association of wildtype HLA-B*2705 with the transporter associated with antigen processing could also be enhanced by mutation of residues at position 114 and 116 in the peptide-binding groove to those present in the HLA-B*2706 allele.ConclusionWe have demonstrated that HLA-B27 heavy-chain homodimer formation can be induced by dendritic cell activation, implying that these novel structures may not be displayed to the immune system at all times. Our data suggests that the behaviour of HLA-B27 on dendritic cells may be important in the study of inflammatory arthritis.

Crystal Structure of a SEA Variant in Complex with MHC Class II Reveals the Ability of SEA to Crosslink MHC Molecules

Although the biological properties of staphylococcal enterotoxin A (SEA) have been well characterized, structural insights into the interaction between SEA and major histocompatibilty complex (MHC) class II have only been obtained by modeling. Here, the crystal structure of the D227A variant of SEA in complex with human MHC class II has been determined by X-ray crystallography. SEA D227A exclusively binds with its N-terminal domain to the α chain of HLA-DR1. The ability of one SEA molecule to crosslink two MHC molecules was modeled. It shows that this SEA molecule cannot interact with the T cell receptor (TCR) while a second SEA molecule interacts with MHC. Because of its relatively low toxicity, the D227A variant of SEA is used in tumor therapy.

Lupus anticoagulants: strong association with the major histocompatibility complex class II and platelet antibodies.

A relationship between the presence of platelet autoantibodies and major histocompatibilty complex class II alleles was determined in 27 patients with lupus anticoagulants. Twenty-two patients had a primary antiphospholipid syndrome' and five patients had lupus erythematosus (SLE). Platelet antibodies against the platelet glycoproteins (GP) IIb/IIIa were detectable in 20 patients. Anti-GPIb/IX or -GPIV antibodies were detectable only in patients with anti-GPIIb/IIIa antibodies. An increased frequency of HLA-DQB1*06 was demonstrable in the total patient population. The association between the lupus anticoagulants and HLA-DQB1*06 was even stronger if patients also had detectable platelet antibodies. This association was also seen if patients with a history of thromboembolic disease were considered separately. However, within the patient population there was no difference between frequencies of HLA alleles detectable platelet antibodies.

The role of major histocompatibility complex polymorphisms on SIV infection in rhesus macaques

To investigate whether Major Histocompatibilty Complex (MHC) polymorphisms influence either susceptibility to SIV infection or progress to actual disease, rhesus monkeys were subjected to various forms of SIV infection and screened for allelic MHC heterogeneity by means of serological and biochemical methods. Animals that are protected against cell associated virus challenges were those that are SIV vaccinated and which shared a particular MHC class I allele (Mamu-A26) with the donor of the infected cells. Comparisons on the rate of infection to AIDS in SIV mac infected macaques showed that most Mamu-A26 positive animals belong to the group of long time survivors. In our outbred colony, about 25% of the rhesus macaques are positive for the Mamu-A26 serotype. Gel electrophoretic analyses demonstrated that isoelectric point (pI) differences of MHC class I heavy chains correlate with allotyping. In addition, the Mamu-A26 specificity was found to display heterogeneity. These results suggest that particular Mamu-A26 (associated) gene products may have the capacity or quality to induce antigen specific cytotoxic T lymphocyte responses that play a key role in controlling SIV infection or vaccine protection.