Effects of HLA-DPB1 genotypes on chronic hepatitis B infection in Japanese individuals

Significant associations of HLA-DP alleles with chronic hepatitis B (CHB) infection are evident in Asian and Arabian populations, including Japanese, Han Chinese, Korean, and Saudi Arabian populations. Here, significant associations between CHB infection and five DPB1 alleles (two susceptibility alleles, DPB1(*) 05:01 and (*) 09:01, and three protective alleles, DPB1(*) 02:01, (*) 04:01, and (*) 04:02) were confirmed in a population comprising of 2582 Japanese individuals. Furthermore, odds ratios for CHB were higher for those with both DPB1 susceptibility alleles than for those with only one susceptibility allele; therefore, effects of susceptibility alleles were additive for risk of CHB infection. Similarly, protective alleles showed an additive effect on protection from CHB infection. Moreover, heterozygotes of any protective allele showed stronger association with CHB than did homozygotes, suggesting that heterozygotes may bind a greater variety of hepatitis B-derived peptides, and thus present these peptides more efficiently to T-cell receptors than homozygotes. Notably, compound heterozygote of the protective allele (any one of DPB1*02:01, *04:01, and *04:02) and the susceptible allele DPB1*05:01 was significantly associated with protection against CHB infection, which indicates that one protective HLA-DPB1 molecule can provide dominant protection. Identification of the HLA-DPB1 genotypes associated with susceptibility to and protection from CHB infection is essential for future analysis of the mechanisms responsible for immune recognition of hepatitis B virus antigens by HLA-DPB1 molecules.

HLA-A, -B, -C, -DRB1 and -DQB1 alleles and haplotypes in the Kinh population in Vietnam

Allele and haplotype frequencies of the human leukocyte antigens (HLA) were studied in the Kinh Vietnamese population. We analyzed 170 unrelated healthy individuals. DNA-based HLA typing was performed using a microsphere-based array genotyping platform with sequence-specific oligonucleotide probes to distinguish HLA-A, -B, -C, -DRB1 and -DQB1 alleles. A total of 21 HLA-A, 37 HLA-B, 18 HLA-C, 25 HLA-DRB1, and 14 HLA-DQB1 alleles were identified. HLA-A*1101, A*2402, A*3303, B*1502, B*4601, Cw*0102, Cw*0702, Cw*0801, DRB1*1202, DQB1*0301, DQB1*0303, and DQB1*0501 were found with frequencies higher than 10%. Two representative haplotypes bearing two to five HLA loci were A*1101-B*1502 and A*3303-B*5801 for HLA-A-B; Cw*0801-B*1502 and Cw*0102-B*4601 for HLA-C-B; B*1502-DRB1*1202 and B*4601-DRB1*0901 for HLA-B-DRB1; DRB1*1202-DQB1*0301 and DRB1*0901-DQB1*0303 for HLA-DRB1-DQB1; A*1101-Cw*0801-B*1502 and A*3303-Cw*0302-B*5801 for HLA-A-C-B; A*1101-B*1502-DRB1*1202 and A*2901-B*0705-DRB1*1001 for HLA-A-B-DRB1, A*1101-Cw*0801-B*1502-DRB1*1202-DQB1*0301 and A*2901-Cw*1505-B*0705-DRB1*1001-DQB1*0501 for HLA-A-C-B-DRB1-DQB1. Allele distribution and haplotype analysis demonstrated that the Vietnamese population shares HLA patterns with southern Chinese, Thai, Javanese and Micronesians, while it also retains unique characteristics.

Search of type 2 diabetes susceptibility gene on chromosome 20q

Significant evidence of linkage to type 2 diabetes (T2D) has been shown in a relatively broad region on chromosome 20q, where the hepatocyte nuclear factor-4alpha (HNF4A) has been noted as a positional candidate. To systematically evaluate genetic susceptibility to T2D in the relevant region, we examined the disease association by using 1145 SNPs in two-step screening in the Japanese population. The marker screening enabled us to identify significant disease association in the lipopolysaccharide binding protein (LBP) but not in the HNF4A locus. In a 17.7-Mb interval screened, the strongest association was identified for a SNP, rs2232592, located in the intron of LBP, with an estimated odds ratio of 1.73 (95% CI 1.30-2.31) (P=0.0002) in the whole study panel involving 675 case and 474 control subjects. Our data suggest that the LBP gene may confer genetic susceptibility to T2D and this warrants further replication study.

STAT1-independent inhibition of cyclooxygenase-2 expression by IFNgamma; a common pathway of IFNgamma-mediated gene repression but not gene activation

Cyclooxygenase-2 (COX-2), the rate-limiting enzyme in the synthesis of prostaglandins, promotes the development of colorectal cancer, and is a key molecular target of non-steroidal anti-inflammatory drugs, compounds that reduce the relative risk of developing colon cancer. In this study, we showed that interferon gamma (IFNgamma) inhibits the expression of COX-2 protein in intestinal epithelial cells (IECs) through a pathway that requires Janus-activated kinase (JAK) activity. In contrast, we demonstrated that transcriptional inhibition of COX-2 by IFNbeta or IFNgamma occurs in cells with silenced signal transducer and activator of transcription 1 (STAT1) expression and that IFNs retained the ability to inhibit COX-2 transcription in cells with activated RasV12, in which IFNgamma failed to induce STAT1. Thus, unlike the activity of JAK, STAT1 is not required for the inhibition of COX-2 expression by IFNgamma. In contrast to COX-2, the activation of genes in response to IFNgamma, such as interferon regulatory factor-1, was severely impaired by both STAT1 silencing and by constitutive Ras signaling. To determine whether there is a general differential requirement for STAT1 in gene activation and gene repression in response to IFNgamma in intestinal cells, we performed genome-wide analysis of IFNgamma target genes in an IEC line in which STAT1 expression was silenced by small interfering RNA. The results confirmed that the activation of the majority of genes by IFNgamma required STAT1. In contrast, the repression of several genes, as we showed for COX-2 specifically, was largely unaffected in cells with silenced STAT1. Our results therefore demonstrate that in general gene activation by IFNgamma is more sensitive to STAT1 deficiency than gene repression, and suggest that IFNgamma activates and represses gene expression via distinct pathways that can be distinguished, at least in part, by their requirement for STAT1.

Detachment-induced upregulation of XIAP and cIAP2 delays anoikis of intestinal epithelial cells

Detachment of normal epithelial cells from the extracellular matrix triggers apoptosis, a phenomenon called anoikis. Conversely, carcinoma cells tend to be relatively more anoikis-resistant than their normal counterparts, and this increased resistance represents a critical feature of the malignant phenotype. Mechanisms that control susceptibility and resistance to anoikis are not fully understood. It is now known that detachment of non-malignant epithelial cells triggers both pro- and antiapoptotic signals, and it is the balance between these signals and the duration of detachment that determine further fate of the cells. Detachment-induced antiapoptotic events delay anoikis and if cells reattach relatively soon after detachment they survive. Direct regulators of apoptosis responsible for this delay of anoikis are unknown. We found that detachment of non-malignant intestinal epithelial cells triggers upregulation of inhibitors of apoptosis protein (IAP) family, such as X-chromosome-linked inhibitor of apoptosis protein and cellular inhibitor of apoptosis-2 (cIAP2). We demonstrated that this upregulation requires detachment-dependent activation of the transcription factor nuclear factor-kappaB. We further observed that various IAP antagonists accelerate anoikis, indicating that upregulation of the IAPs delays detachment-triggered apoptosis. We conclude that the IAPs are important regulators of the balance between detachment-triggered life and death signals. Perhaps, not by coincidence, these proteins are often upregulated in carcinomas, tumors composed of cells that tend to be anoikis-resistant.

Identification of novel MUNC13-4 mutations in familial haemophagocytic lymphohistiocytosis and functional analysis of MUNC13-4-deficient cytotoxic T lymphocytes

BACKGROUND

Familial haemophagocytic lymphohistiocytosis (FHL) has an autosomal recessive mode of inheritance and consists of at least three subtypes. FHL2 subtype with perforin (PRF1) mutation accounts for 30% of all FHL cases, while FHL with MUNC13-4 mutation was recently identified and designated as FHL3 subtype.

OBJECTIVE

To examine MUNC13-4 mutations and the cytotoxic function of MUNC13-4 deficient T lymphocytes in Japanese FHL patients

METHODS

Mutations of MUNC13-4 and the cytotoxicity of MUNC13-4-deficient cytotoxic T lymphocytes (CTL) were analysed in 16 Japanese families with non-FHL2 subtype.

RESULTS

Five new mutations of the MUNC13-4 gene were identified in six families. The mutations were in the introns 4, 9, and 18, and exons 8 and 19. Two families had homozygous mutations, while the remaining four had compound heterozygous mutations. Cytotoxicity of MUNC13-4 deficient CTL was low compared with control CTL, but was still present. Clinically, the onset of disease tended to occur late; moreover, natural killer cell activity was not deficient in some FHL3 patients.

CONCLUSIONS

MUNC13-4 mutations play a role in the development of FHL3 through a defective cytotoxic pathway.

Assessment of synthetic peptides of severe acute respiratory syndrome coronavirus recognized by long-lasting immunity

Abstract:  In order to determine highly immunogenic severe acute respiratory syndrome coronavirus (SARS‐CoV) epitope peptides capable of inducing long‐lasting immunity, we first screened immunoglobulin‐G (IgG) antibodies reactive to 197 different overlapping 15‐mers from the SARS‐CoV proteins in the sera of three infected patients. Forty‐two peptides among them were reactive to the sera from all three patients. Consequently, we tested for the reactivity of these 42 peptides to patients' sera (n = 45) at 6‐month post‐infection. The significantly higher levels of IgG antibodies specific to three (S791, M207 and N161) of 42 peptides were detectable in the post‐infection sera from 23 (51%), 27 (60%) and 19 (42%) of 45 patients, respectively. These three peptides, recognized by their long‐lasting immunity, may provide a better understanding of the immunogenicity of SARS‐CoV.

Segregation analysis of IgE responses to Cryptomeria japonica pollen antigen in vivo

The IgE response to Cryptomeria japonica pollen antigen (CPAg) in vivo was determined by radioimmunoassay of the plasma of 525 members from 98 families with known nasal allergies. Based on responses, patients were classified into a non-responder or low-responder group (non/low) and a high-responder group. Segregation analysis revealed that the IgE non/low responsiveness to CPAg involved a single dominant trait. The gene frequency was calculated to be 0.44-0.60. The IgE non/low response to CPAg was found to be mediated by CPAg-specific suppressor T cells. These findings demonstrated that the phenotypic variation of IgE responsiveness to CPAg is not due the immune response gene, but rather is mediated by the immune suppression gene for CPAg, via CPAg-specific suppressor T cells.

Polymorphisms in TNFA and TNFR2 affect outcome of unrelated bone marrow transplantation

Effects of polymorphisms in TNFA and TNFR2 on the outcome of 462 cases of unrelated bone marrow transplantation (uBMT) were studied retrospectively. Four alleles of TNFA (U01-U04) distinguished by polymorphism in the upstream region, -1031 (T/C), -863 (C/A) and -857 (C/T), and two alleles of TNFR2 (196M/196R) distinguished by polymorphism at codon 196 were determined. Transplantation involving TNFA-U02- and/or U03-positive donors and/or recipients resulted in a higher incidence of graft-versus-host disease (GVHD) of grade III-IV (P < 0.05 for donor type, P < 0.01 for recipient type) and a lower relapse rate than that involving TNFA-U01 homozygous recipients and/or donors (P < 0.025 for donor type, P < 0.01 for recipient type). These results include the HLA mismatching effect due to linkage disequilibirium of TNFA with HLA loci. However, the effects were also observed in HLA-A, -B and -DRB1 allele-matched transplantation. Transplantation from TNFR2-196R-positive donors exhibited a higher incidence of severe GVHD (P < 0.05) and tendency for a lower relapse rate than that from TNFR2-196M homozygous donors. TNFR2-196R of recipient origin had no effect on GVHD but increased the relapse rate (P < 0.025). These results suggest that TNFA and TNFR2 typings are helpful for predicting uBMT outcome and for preventing severe complications at an early stage.

Combination of HLA-A and HLA class II alleles controls the susceptibility to rheumatoid arthritis

Two hundred and four unrelated Japanese patients with rheumatoid arthritis (RA) were typed for HLA by serological typing and DNA typing. The serological typing revealed that frequencies of HLA-A11, DR4, DR53 and DQ4 were increased and those of DR8 and DQ1 were decreased in the patients. The DNA typing has precisely defined the disease-associated HLA class II alleles; DRBl*0405, DQAl*03 and DQBl*0401 showed positive associations, while negative associations were found with DRBl*0803, DQAl*0103 and DQBl*0601. The risk for RA was found to be closely associated with particular amino acid sequences of DR-beta chain, including glycine residue at the 86th position in addition to those between 70 and 74, which are known to confer binding specificity and affinity to antigenic peptides. The observation that the frequency of HLA-A11 was increased in the DRBl*0405-positive patients suggested the interaction of these two alleles in the susceptibility to RA. On the other hand, the frequency of DPB1*0201 was increased in the DRBl*0405-negative patients and the frequency of HLA-A2 was increased in the DPBl*0201-positive patients, especially in the younger onset group. These findings suggested that the combination of HLA-A2 and DPBl*0201 may confer the susceptibility in the DRBl*0405-negative patients. Our results suggested the possibility that the susceptibility to RA is controlled by the interaction of HLA-A and DRBl genes or by that of HLA-A and DPBl genes in different patient subgroups.

Organ-specific autoimmunity in mice whose T cell repertoire is shaped by a single antigenic peptide

Organ-specific autoimmune diseases have been postulated to be the result of T cell response against organ-specific self-peptides bound to MHC molecules. Contrary to this paradigm, we report here that transgenic mice lacking MHC class I expression and expressing an MHC class II I-A(b) molecule that presents only a single peptide (E alpha 52-68) spontaneously develops peripheral nervous system-specific autoimmune disease with many of the histopathological features found in experimental allergic neuritis. Reciprocal bone marrow chimeras produced using susceptible and resistant lines revealed that bone marrow-derived cells determined disease susceptibility. While the expression of the I-A(b)-E alpha 52-68 complex in the periphery was readily detectable in both lines, its expression on thymic dendritic cells responsible for tolerance induction was markedly lower in the susceptible line than in the resistant line. Consistent with this, CD4(+) T cells that can be activated by the I-A(b)-E alpha 52-68 complex were found in the susceptible line, but not in the resistant line. Such CD4(+) T cells conferred the disease to the resistant line by adoptive transfer, and administration of Ab specific for the I-A(b)-E alpha 52-68 complex inhibited disease manifestation in the susceptible line. These results indicate that disease development involves systemic T cell reactivity to I-A(b)-E alpha 52-68 complex, probably caused by incomplete negative thymocyte selection.

Comparative analysis of HLA restriction and cytokine production in hepatitis B surface antigen-specific T cells from low- and high-antibody responders in vaccinated humans

It is well known that individuals with low, or lack of, antibody production in response to hepatitis B surface antigen (HBsAg) exist in the human population. We have previously reported that HLA class I and class II genes are both involved in antibody production to HBsAg, and that specific alleles of HLA are associated with low and high antibody production. To elucidate further the mechanisms by which the diversity of antibody production to HBsAg is generated in humans, a total of 146 T-cell clones specific for HBsAg were produced from six healthy vaccinees (three low- and three high-antibody responders) and were examined for cytokine production and HLA restriction. It was found that the majority of the T-cell clones from the low-antibody responders were Th1- or Th0-like T cells (62% or 19%, respectively), whereas the majority of T-cell clones from the high-antibody responders were Th2-like T cells (77%), suggesting predominant expansion of Th1/Th0- and Th2-like T cells specific for HBsAg in the low- and high-antibody responders, respectively. This is the first evidence that the diversity of the response to HBsAg in humans is controlled by the activation of functionally distinct CD4+ T-cell subsets, i.e., Th0, Th1, or Th2 T cells.

Polymorphisms in the coding region of mtDNA and effects on clinical outcome of unrelated bone marrow transplantation

The entire protein-coding region was divided into 45 fragments, separately amplified and analyzed for polymorphism by the PCR-SSCP (single-strand conformation polymorphism) method. The effect of polymorphism mismatching on the clinical outcome of unrelated bone marrow transplantation was studied to clarify whether products from mtDNA become minor antigens. Variability in PCR-SSCP pattern combinations of the 45 fragments suggests that each individual has a different polymorphism combination in the protein-coding region if all the coding regions were compared at the nucleotide sequence level. Nonsynonymous polymorphisms were found at relatively high frequency in MTATP8 and MTND3. Both the polymorphisms with and without substitution matched the peptide-binding motifs of HLA-A*0201. The effects of the polymorphism matching were retrospectively analyzed in 340 recipients transplanted with HLA-A, -B, -DRB1 allele-matched bone marrow from unrelated donors. There were no effects of polymorphism matching on the incidence of acute GVHD and cumulative disease-free survival. These results suggest that polymorphisms which generate peptides, with and without substitutions, that bind the same HLA molecule hardly influence GVHD because the difference between the HLA-peptide complexes is minute.

Haematopoietic cell-specific CDM family protein DOCK2 is essential for lymphocyte migration

Cell migration is a fundamental biological process involving membrane polarization and cytoskeletal dynamics, both of which are regulated by Rho family GTPases. Among these molecules, Rac is crucial for generating the actin-rich lamellipodial protrusion, a principal part of the driving force for movement. The CDM family proteins, Caenorhabditis elegans CED-5, human DOCK180 and Drosophila melanogaster Myoblast City (MBC), are implicated to mediate membrane extension by functioning upstream of Rac. Although genetic analysis has shown that CED-5 and Myoblast City are crucial for migration of particular types of cells, physiological relevance of the CDM family proteins in mammals remains unknown. Here we show that DOCK2, a haematopoietic cell-specific CDM family protein, is indispensable for lymphocyte chemotaxis. DOCK2-deficient mice (DOCK2-/-) exhibited migration defects of T and B lymphocytes, but not of monocytes, in response to chemokines, resulting in several abnormalities including T lymphocytopenia, atrophy of lymphoid follicles and loss of marginal-zone B cells. In DOCK2-/- lymphocytes, chemokine-induced Rac activation and actin polymerization were almost totally abolished. Thus, in lymphocyte migration DOCK2 functions as a central regulator that mediates cytoskeletal reorganization through Rac activation.

A novel autosomal dominant spinocerebellar ataxia (SCA16) linked to chromosome 8q22.1-24.1

OBJECTIVE

To characterize a distinct form of autosomal dominant cerebellar ataxia (ADCA) clinically and genetically.

BACKGROUND

ADCAs are a clinically, pathologically, and genetically heterogeneous group of neurodegenerative disorders. Nine responsible genes have been identified for SCA-1, -2, -3, -6, -7, -8, -10, and -12 and dentatorubral-pallidoluysian atrophy (DRPLA). Loci for SCA-4, -5, -11, -13, and -14 have been mapped.

METHODS

The authors studied a four-generation Japanese family with ADCA. The 19 members were enrolled in this study. The authors performed the mutation analysis by PCR and a genome-wide linkage analysis.

RESULTS

Nine members (five men and four women) were affected. The ages at onset ranged from 20 to 66 years. All affected members showed pure cerebellar ataxia, and three patients also had head tremor. Head MRI demonstrated cerebellar atrophy without brain stem involvement. The mutation analysis by PCR excluded diagnoses of SCA-1, -2, -3, -6, -7, -8, and -12 and DRPLA. The linkage analysis suggested linkage to a locus on chromosome 8q22.1-24.1, with the highest two-point lod score at D8S1804 (Z = 3.06 at theta = 0.0). The flanking markers D8S270 and D8S1720 defined a candidate region of an approximately 37.6-cM interval. This candidate region was different from the loci for SCA-4, -5, -10, -11, -13, and -14.

CONCLUSION

The family studied had a genetically novel type of SCA (SCA-16).

Identification of susceptibility loci for autoimmune thyroid disease to 5q31-q33 and Hashimoto's thyroiditis to 8q23-q24 by multipoint affected sib-pair linkage analysis in Japanese

Autoimmune thyroid disease (AITD), including Graves' disease (GD) and Hashimoto's thyroiditis (HT), is caused by multiple genetic and environmental factors. The clinical and immunological features of GD and HT are distinct; however, there are multiplex families with both GD and HT, and cases in which GD evolves into HT. Thus, there may be specific susceptibility loci for GD or HT, and common loci controlling the susceptibility to both GD and HT may exist. A genome-wide analysis of data on 123 Japanese sib-pairs affected with AITD was made in which GD- or HT-affected sib-pairs (ASPs) were studied to detect GD- or HT-specific susceptibility loci, and all AITD-ASPs were used to detect AITD-common susceptibility loci. Our study revealed 19 regions on 14 chromosomes (1, 2, 3, 5, 6, 8, 9, 10, 11, 12, 13, 15, 18 and 22) where the multipoint maximum LOD score (MLS) was >1. Especially, chromosome 5q31-q33 yielded suggestive evidence for linkage to AITD as a whole, with an MLS of 3.14 at D5S436, and chromosome 8q23-q24 yielded suggestive evidence for linkage to HT, with an MLS of 3.77 at D8S272. These observations suggest the presence of an AITD susceptibility locus at 5q31-q33 and a HT susceptibility locus at 8q23-q24.

Genetic variability and linkage disequilibrium within the HLA-DP region: analysis of 15 different populations

In order to understand the forces governing the evolution of the genetic diversity in the HLA-DP molecule, polymerase chain reaction (PCR)-based methods were used to characterize genetic variation at the DPA1 and DPB1 loci encoding this heterodimer on 2,807 chromosomes from 15 different populations including individuals of African, Asian, Amerindian, Indian and European origin. These ethnically diverse samples represent a variety of population substructures and include small, isolated populations as well as larger, presumably admixed populations. Ten DPA1 and 39 DPB1 alleles were identified and observed on 87 distinct DP haplotypes, 34 of which were found to be in significant positive linkage disequilibrium in at least one population. Some haplotypes were found in all ethnic groups while others were confined to a single ethnic group or population. Strong positive global linkage disequilibrium (Wn) between DPA1 and DPB1 was present in all 15 populations. The African populations displayed the lowest values of Wn whereas the Amerindian populations displayed near absolute disequilibrium. Analysis of the distribution of haplotypes using the normalized deviate of the Ewens-Watterson homozygosity statistic, F, suggests that DP haplotypes encoding the functional heterodimer are subject to much lower degrees of balancing selection than other loci within the HLA region. Finally, neighbor joining tree analyses demonstrate the power of haplotype diversity for inferring the relationships between the different populations.

The role of HLA matching in hematopoietic cell transplantation

Hematopoietic cell transplantation (HCT) can be a life-saving therapy for patients with genetic and acquired hematologic diseases. Despite major advances in supportive care during HCT, immunological complications of the alloimmune response, including graft rejection and graft-versus-host disease (GVHD), remain major impediments to successful clinical outcomes. Although graft rejection mediated by host immune cells and GVHD mediated by donor immune cells can be prevented or mediated by immune suppression therapy, genetic HLA matching remains essential for successful strategies designed to minimize the risks of transplantation. The most favorable HCT results are seen in patients with a genotypically HLA-identical sibling donor, but the limited availability of matched related donors has severely restricted the clinical application of this therapy. Fortunately, the establishment of large unrelated volunteer donor registries now provides the opportunity to identify HLA matches for many patients who lack a family donor. The criteria for unrelated donor matching, however, are poorly defined. Until recently, an analysis of matching beyond HLA-identical siblings has been limited by typing technology. The introduction within the past few years of new methods for high resolution typing and definition of HLA alleles has had a profound impact on our ability to identify and interpret the multiple nucleotide sequence polymorphisms that encode HLA antigens. Preliminary studies clearly demonstrate the importance of precise matching at the allele level for successful transplantation. There remain, however, important unanswered questions about the relative importance of different HLA loci in matching strategies, as well as incomplete information about permissible limits of mismatching in different patient populations.

A second susceptibility gene for developing rheumatoid arthritis in the human MHC is localized within a 70-kb interval telomeric of the TNF genes in the HLA class III region

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease with a multifactorial genetic basis. However, pathogenic genes for RA other than the human leukocyte antigen (HLA)-DRB1 gene have yet to be identified. Here, we investigated whether there is a second susceptibility locus for RA within the human major histocompatibility complex using 18 microsatellite markers distributed from the centromeric (HSET) to the telomeric end (P5-15) of the 3.6-Mb HLA region. Statistical studies of associated alleles on each microsatellite locus showed that one pathogenic gene for RA in the HLA region is localized in the DRB1 gene, as expected. Further, a second susceptibility gene of RA was suggested to be present in the HLA class III region, narrowed to 70 kb, that is just telomeric of the TNF gene cluster (TNFA and LTA) and that is located between the microsatellites TNFa and C1-2-A. In this critical segment, four expressed genes have been thus far identified, NFKBIL1 (IkappaBL), ATP6G, BAT1, and MICB, all of which are candidate genes for determining susceptibility to RA. These results exclude the possibility of involvement of the TNFA genes (TNF-alpha) in the development of RA, which was suggested previously to be a strong candidate for RA in the class III region.

Quantitation of HLA-A*0201 bound tumor associated antigens on a peptide pulsed B cell line

CTLs recognize 8- to 10-mer peptides on MHC class I molecules. Recent studies have shown that human CTLs kill autologous tumor cells in an HLA-restricted and peptide-specific manner, and that artificial pep- tides can stimulate tumor-specific CTLs both in vitro and in vivo. Accordingly, several human clinical trials using such peptides are ongoing worldwide. In such methods, the amount of peptide-MHC complexes that remain on the cell surface of APCs after peptide administration is crucial, because CTL activation depends on the number of ligated TCRs and co-stimulation. However, it remains uncertain how many peptide-MHC complexes are reconstituted and remain on live cells after peptide administration. We herein examined the binding affinities of five HLA-A*0201 restricted peptides-four TAAs and one HIV antigen-to HLA-A*0201 molecules and their decay rates on a live B cell line using tandem mass spectrometry. Our experiments showed that nearly 10(5) peptide-MHC complexes per cell could be reconstituted on a cell surface by pulsing a high dose of peptide even if the binding affinities were intermediate or low. However, the decay rates observed for these pep- tide-MHC complexes on a B cell line were faster than previously estimated.

Lack of association between the Met196Arg polymorphism in the TNFR2 gene and autoimmune diseases accompanied by vasculitis including SLE in Japanese

A polymorphism in high-affinity receptor of TNF (TNFR2) gene, Met196Arg, was reported to be associated with systemic lupus erythematosus (SLE) in Japanese, whereas the association could not be found in Europeans at all and this represents an apparent discrepancy. The association, then, should be tested in other populations to clarify the possible involvement, if any, of the TNFR2 polymorphism in SLE or other related autoimmune diseases. The purposes of this study were to examine the TNFR2 polymorphism in Japanese patients with SLE and to investigate its association with other autoimmune diseases accompanied by vasculitis, mixed connective tissue disease, Buerger's disease, and Takayasu's arteritis. We found no association at all between the TNFR2 polymorphism and any autoimmune diseases including SLE in Japanese.

Involvement of deregulated epiregulin expression in tumorigenesis in vivo through activated Ki-Ras signaling pathway in human colon cancer cells

To identify the genes located downstream of the activated Ki-Ras signaling pathways in human colon cancer cells, a PCR-based cDNA subtraction library was constructed between HCT116 cells and HCT116-derived activated Ki-ras-disrupted cells (HKe3). One of the genes in HCT116 that was evidently up-regulated was epiregulin, a member of the epidermal growth factor family that is expressed in many kinds of human cancer cells. HKe3-stable transfectants expressing activated Ki-Ras regained over-expression of epiregulin. To further elucidate the biochemical structure and significance of epiregulin expression in tumorigenesis, HKe3-stable transfectants expressing epiregulin (e3-pSE cells) were established. Epiregulin existed as highly glycosylated membrane-bound forms, and TPA rapidly induced ectodomain shedding of epiregulin. Furthermore, the conditioned medium of e3-pSE cells showed more DNA synthesis for 32D cells expressing epidermal growth factor receptor (DER) cells than that of HKe3. Although anchorage-independent growth in soft agar was not observed for e3-pSE cells, tumorigenicity in nude mice was observed evidently, and their growth rate was correlated with each amount of exogenous epiregulin expression. These results suggested that activated Ki-Ras will be one of the factors contributing to the overexpression of epiregulin in human colon cancer cells, and that epiregulin will play a critical role in human tumorigenesis in vivo.

Diversity of T cell repertoire shaped by a single peptide ligand is critically affected by its amino acid residue at a T cell receptor contact

T cell differentiation in the thymus is driven by positive selection through the interaction of alphabeta T cell receptors (TCRs) with self-peptides bound to self-major histocompatibility complex molecules, yet the influence of the peptide sequence on this process remains unknown. To address this issue, we have compared CD4(+) T cell differentiation between two sets of mouse lines in which MHC class II I-A(b) molecules are occupied with either Ealpha chain-derived peptide ((p)Ealpha) or its variant, (p)60K, with one amino acid substitution from leucine to lysine at P5 residue of TCR contacts. Here, we show that despite the comparable expression of I-A(b)-peptide complex in the thymus, this substitution from leucine to lysine affects efficiency of positive selection, resulting in extremely small numbers of CD4(+) T cells to be selected to mature on I-A(b)-(p)60K complex. Furthermore, we show that, although I-A(b)-(p)Ealpha complex selects diverse T cells, T cell repertoire shaped by I-A(b)-(p)60K complex is markedly constrained. Our findings thus suggest that positive selection is both specific and degenerate, depending on the amino acid residues at TCR contacts of the selecting self-peptides.

Changes at the floor of the peptide-binding groove induce a strong preference for proline at position 3 of the bound peptide: molecular dynamics simulations of HLA-A*0217

We report on molecular dynamics simulations of major histocompatibility complex (MHC)-peptide complexes. Class I MHC molecules play an important role in cellular immunity by presenting antigenic peptides to cytotoxic T cells. Pockets in the peptide-binding groove of MHC molecules accommodate anchor side chains of the bound peptide. Amino acid substitutions in MHC affect differences in the peptide-anchor motifs. HLA-A*0217, human MHC class I molecule, differs from HLA-A*0201 only by three amino acid residues substitutions (positions 95, 97, and 99) at the floor of the peptide-binding groove. A*0217 showed a strong preference for Pro at position 3 (p3) and accepted Phe at p9 of its peptide ligands, but these preferences have not been found in other HLA-A2 ligands. To reveal the structural mechanism of these observations, the A*0217-peptide complexes were simulated by 1000 ps molecular dynamics at 300 K with explicit solvent molecules and compared with those of the A*0201-peptide complexes. We examined the distances between the anchor side chain of the bound peptide and the pocket, and the rms fluctuations of the bound peptides and the HLA molecules. On the basis of the results from our simulations, we propose that Pro at p3 serves as an optimum residue to lock the dominant anchor residue (p9) tightly into pocket F and to hold the peptide in the binding groove, rather than a secondary anchor residue fitting optimally the complementary pocket. We also found that Phe at p9 is used to occupy the space created by replacements of three amino acid residues at the floor within the groove. These findings would provide a novel understanding in the peptide-binding motifs of class I MHC molecules.

Opposing effects of Ras on p53: transcriptional activation of mdm2 and induction of p19ARF

Mdm2 acts as a major regulator of the tumor suppressor p53 by targeting its destruction. Here, we show that the mdm2 gene is also regulated by the Ras-driven Raf/MEK/MAP kinase pathway, in a p53-independent manner. Mdm2 induced by activated Raf degrades p53 in the absence of the Mdm2 inhibitor p19ARF. This regulatory pathway accounts for the observation that cells transformed by oncogenic Ras are more resistant to p53-dependent apoptosis following exposure to DNA damage. Activation of the Ras-induced Raf/MEK/MAP kinase may therefore play a key role in suppressing p53 during tumor development and treatment. In primary cells, Raf also activates the Mdm2 inhibitor p19ARF. Levels of p53 are therefore determined by opposing effects of Raf-induced p19ARF and Mdm2.

Magnitude of structural changes of the T-cell receptor binding regions determine the strength of T-cell antagonism: molecular dynamics simulations of HLA-DR4 (DRB1*0405) complexed with analogue peptide

In our model system, we generated T cell clones specific for the HLA-DR4 (DRB1*0405)-index peptide (YWALEAAAD) complex. Based on response patterns of the T cell clones, analogue peptides containing single amino acid substitutions of the index peptide were classified into three types, agonists, antagonists or null peptides (non-agonistic and non-antagonistic peptides). Subtle structural changes induced by the antagonists in the T-cell receptor (TCR) binding regions have already been explained using the root mean square (r.m.s.) deviations from the DR4-index peptide complex in the molecular dynamics (MD) trajectory. In this work, we performed additional MD simulations at 300 K with explicit solvent molecules to reveal the structural character of the HLA-DR4 complexed with the analogue peptides. We examined the r.m.s. deviations of the TCR-binding sites and the exposed areas of the bound peptides. Remarkable differences of the r.m.s. deviations among the DR4-antagonist complexes, together with our previous data, suggest that the magnitude of structural changes of TCR-binding regions would determine the strength of TCR antagonism. The simulations also indicate that TCR could discriminate null peptides from other ligands mainly through the changes of exposed side chains of the bound peptide, rather than the conformational changes of TCR-binding surfaces on HLA molecule.

Hla-DR2-restricted responses to proteolipid protein 95-116 peptide cause autoimmune encephalitis in transgenic mice

In multiple sclerosis (MS) patients who carry the Class II major histocompatibility (MHC) type HLA-DR2, T cells specific for amino acids 95-116 in the proteolipid protein (PLP) are activated and clonally expanded. However, it remains unclear whether these autoreactive T cells play a pathogenic role or, rather, protect against the central nervous system (CNS) damage. We have addressed this issue, using mice transgenic for the human MHC class II region carrying the HLA-DR2 (DRB1* 1502) haplotype. After stimulating cultured lymph node cells repeatedly with PLP95-116, we generated 2 HLA-DR2-restricted, PLP95-116-specific T-cell lines (TCLs) from the transgenic mice immunized with this portion of PLP. The TCLs were CD4+ and produced T-helper 1 (Th1) cytokines in response to the peptide. These TCLs were adoptively transferred into RAG-2/2 mice expressing HLA-DR2 (DRG1* 1502) molecules. Mice receiving 1 of the TCLs developed a neurological disorder manifested ataxic movement without apparent paresis on day 3, 4, or 5 after cell transfer. Histological examination revealed inflammatory foci primarily restricted to the cerebrum and cerebellum, in association with scattered demyelinating lesions in the deep cerebral cortex. These results support a pathogenic role for PLP95-116-specific T cells in HLA-DR2+ MS patients, and shed light on the possible correlation between autoimmune target epitope and disease phenotype in human CNS autoimmune diseases.

Rnx deficiency results in congenital central hypoventilation

The genes Tlx1 (Hox11), Enx (Hox11L2, Tlx-2) and Rnx (Hox11L2, Tlx-3) constitute a family of orphan homeobox genes. In situ hybridization has revealed considerable overlap in their expression within the nervous system, but Rnx is singularly expressed in the developing dorsal and ventral region of the medulla oblongata. Tlx1-deficient and Enx-deficient mice display phenotypes in tissues where the mutated gene is singularly expressed, resulting in asplenogenesis and hyperganglionic megacolon, respectively. To determine the developmental role of Rnx, we disrupted the locus in mouse embryonic stem (ES) cells. Rnx deficient mice developed to term, but all died within 24 hours after birth from a central respiratory failure. The electromyographic activity of intercostal muscles coupled with the C4 ventral root activity assessed in a medulla-spinal cord preparation revealed a high respiratory rate with short inspiratory duration and frequent apnea. Furthermore, a coordinate pattern existed between the abnormal activity of inspiratory neurons in the ventrolateral medulla and C4 motorneuron output, indicating a central respiratory defect in Rnx mice. Thus, Rnx is critical for the development of the ventral medullary respiratory centre and its deficiency results in a syndrome resembling congenital central hypoventilation.

Linkage analysis of moyamoya disease on chromosome 6

Genetic factors have been suggested to contribute to the etiology of moyamoya disease. The authors have previously reported an association between moyamoya disease and several alleles for human leukocyte antigens (HLA). To further specify the genetic component of moyamoya disease, a linkage study of moyamoya disease using markers on chromosome 6, where the HLA gene is located, was performed. The 15 microsatellite markers of chromosome 6 were studied in 20 affected sibling pairs. From an identical-by-descent analysis of these markers, an allele with possible linkage to moyamoya disease was identified. Sharing of the allele among affected members in 19 families was investigated, considering the haplotype. The marker, D6S441, might be linked to moyamoya disease. Considering the haplotype, the allele was shared among the affected members in 16 (82%) of the 19 families, but not in two others. In one family, sharing of the allele could not be determined because of low heterozygosity. Further studies are necessary to clarify multiple genetic factors that are definitely linked with moyamoya disease.

Analysis of tumor necrosis factor-alpha promoter polymorphism in type 1 diabetes: HLA-B and -DRB1 alleles are primarily associated with the disease in Japanese

Polymorphisms in the 5'-flanking region of the tumor necrosis factor (TNF)-alpha gene were examined to study the genetic background of type 1 diabetes in Japanese. Five different biallelic polymorphisms were examined in 136 type 1 diabetic patients and 300 control subjects. The frequencies of individuals carrying TNF-alpha-857T allele (designated as TNFP-D allele) or -863A/-1,031C allele (designated as TNFP-B allele) were significantly increased in the patients as compared with the controls. Since these TNF-alpha alleles are in linkage disequilibria with certain DRB1 and HLA-B alleles, two-locus analyses were carried out. The TNFP-D allele did not increase the risk in either the presence or absence of the DRB1*0405 or HLA-B54 allele, while the DRB1*0405 and HLA-B54 alleles per se could confer susceptibility in both the TNFP-D allele-positive and -negative populations. Moreover, an odds ratio was remarkably elevated in the population carrying both DRB1*0405 and HLA-B54. Similarly, the TNFP-B allele did not show significant association with the disease in either the HLA-B61-positive or -negative population, while the HLA-B61 allele could significantly increase the risk in the TNFP-B allele-positive population. These data suggest that the associations of TNFP-D and -B alleles may be secondary to their linkage disequilibria with the susceptible HLA class I and class II alleles. Because HLA-B and DRB1 genes were independently associated, both of these genes may be contributed primarily to the pathogenesis of type 1 diabetes in Japanese.

Identification of a genetic risk factor for systemic juvenile rheumatoid arthritis in the 5'-flanking region of the TNFalpha gene and HLA genes

OBJECTIVE

To study polymorphisms in the 5'-flanking promoter/enhancer region of the tumor necrosis factor alpha (TNFalpha) gene and in the coding regions of HLA class I and class II genes, in order to better understand the genetic background of juvenile rheumatoid arthritis (JRA).

METHODS

One hundred eleven Japanese JRA patients (50 with systemic disease, 29 with pauciarticular disease, and 32 with polyarticular disease) and 575 healthy Japanese subjects were examined for the allele frequencies of the TNFalpha, HLA-A, and HLA class II (DRB1, DRB3, DRB4, DRB5, DQA1, DQB1, DPA1, and DPB1) genes, by DNA typing using the polymerase chain reaction-sequence-specific oligonucleotide probe method.

RESULTS

The frequencies of the polymorphic allele at positions -1,031 (T to C substitution, termed -1,031C), -863 (C to A, termed -863A), and -857 (C to T, termed -857T) of the TNFalpha gene in patients with systemic JRA, but not in those with polyarticular or pauciarticular JRA, were significantly higher than in the healthy controls. The allele frequencies of DRB1*0405 and DQB1*0401 in systemic JRA, but not in the other JRA types, were significantly higher than in controls. Linkage analysis showed that the presence of both the TNFalpha -857T allele and DRB1*0405 yielded a significantly increased odds ratio (3.84), while the presence of only 1 of them did not yield a high odds ratio (0.87 and 1.58).

CONCLUSION

The -1,031C/-863A allele and the -857T allele of the TNFalpha gene, both of which are related to high production of tumor necrosis factor alpha, are associated with systemic JRA. The -857T allele may enhance the effect of the DRB1*0405/DQB1*0401 haplotype in predisposing to development of systemic JRA.

Analysis of 500 bone marrow transplants from unrelated donors (UR-BMT) facilitated by the Japan Marrow Donor Program: confirmation of UR-BMT as a standard therapy for patients with leukemia and aplastic anemia

In December 1991, the Japan Marrow Donor Program (JMDP) was established with the cooperation of the Japanese Red Cross and Japan Marrow Donor Foundation under the auspices of the Ministry of Health and Welfare in Japan. By December 1998, 122365 HLA-A,B typed volunteer marrow donors and 7207 patients had been cumulatively registered in the JMDP. The results of HLA-matching between donors and patients revealed that 5684 out of 7207 (78.9%) patients could have at least one HLA-A,B,DR serologically matched donor. Among these matched pairs, 1829 unrelated bone marrow transplants (UR-BMT) were performed. The initial 500 UR-BMT transplanted from January 1993 to October 1995 were analyzed as of July 1998. Engraftment was achieved in 95% of cases. Probability of the occurrence of grade III and IV acute GVHD was 18.4%. The rate of disease-free survival (DFS) of the patients who had standard-risk leukemia and did not suffer from grade III or IV acute GVHD (n = 154) was 60-71% and the rate of survival of patients with aplastic anemia was 56%. It can be stated that UR-BMT is a modality of treatment which is as effective as related BMT if the occurrence of grade III or IV acute GVHD is predicted and prevented.

A new predictive model for insulin-dependent diabetes mellitus susceptibility based on combinations of molecular HLA-DRB1 and HLA-DQB1 pockets

With a view to establishing an accurate evaluation of the genetic predisposition to insulin-dependent type I diabetes (IDDM), we have built a model based on the characteristics of the relevant pockets of HLA-DR and -DQ molecules. Three independent populations were investigated. Group I and group II were Caucasoids, while group III was Japanese, including a total of 1,166 IDDM patients and 2,391 healthy controls. We formulate the hypothesis that suceptibility to IDDM is not only explained by the absence of Aspartate 57 (negative charge) from pocket 9 of DQB1 (P9DQ), but also by the presence of an electric charge (+/- vs. neutral), generated by residues 70, 71 and 74 in pockets 4 of DRB1 (P4DR) and DQB1 (P4DQ) molecules. The respective weight of each pocket, was evaluated in a multivariate analysis based on the logistic regression method. The 4 components (2 loci and 2 pockets) were systematically analysed in the computer model. It was clearly shown that the structural characteristics of pockets P9DQ-P4DR and, to a lesser degree that of P4DQ, account for IDDM predisposition. On applying the model to the whole international series, it appears that the highest risk concerns individuals with P9DQ non-Asp 57 and both the charged P4 of DRB1 and P4 of DQB1, conferring a 80% prediction of susceptibility. Conversely, P9DQ Asp and neutral P4DR and P4DQ give the lowest risk with a predictive value of 5%. This model of risk susceptibility prediction fits remarkably well with the observed distribution in a worldwide study. It allows a better evaluation of the respective role of HLA-DR and -DQ molecules as a major component of susceptibility to IDDM.

DNA typing of HLA class II genes (HLA-DR, -DQ and -DP) in Japanese patients with histiocytic necrotizing lymphadenitis (Kikuchi's disease)

The pathogenesis of histiocytic necrotizing lymphadenitis (HNL), which was reported first by Kikuchi et al. and Fujimoto et al. in 1972, is as yet unknown. HNL is frequently reported in Asian countries including Japan, however it is rare in Europe and North America. To elucidate whether the human leukocyte antigen (HLA) alleles and haplotypes are associated with HNL, we performed DNA typing of HLA class II genes (HLA-DR, -DQ, and -DP) in 86 patients with HNL and 525 unrelated healthy Japanese controls with polymerase chain reaction using sequence-specific oligonucleotide probes (PCR-SSOP). In this study, we found DPA1*01 and DPB1*0202 allele frequencies in HLA class II genes are significantly higher in HNL patients than in normal controls. It is known that the frequency of DPB1*0202 alleles is extremely low or absent in Caucasians (e.g., French 0.4%, Italian 0.8%) and Negroid (e.g., South African 0%, Hottentot 0%), but relatively frequent in Asians (e.g., Korean 9.9%, Japanese 4.5%). Previous reports have said the incidence of HNL is frequent in Asians but rare in other races. In light of this background, HLA class II genes of HNL and the incidence of HNL in Asian countries, including Japan, might have a positive relationship to DPA1*01 and DPB1*0202 allele.