RESUMO
We previously reported that a disparate distribution between killer cell immunoglobulin-like receptor (KIR) and human leukocyte antigen (HLA) class 1 genes is associated with susceptibility to develop type 1 diabetes. Here we compare multiple models which reflect the combined genotype effects of combinations of functional inhibitory and activating KIRs in relation to HLA in an extended cohort of patients with juvenile-onset type 1 diabetes and non-diabetic control subjects. Our results suggest that autoimmunity in type 1 diabetes is mainly associated with a decrease in inhibitory KIR-HLA genotype combinations, while the influence of activating KIR genotypes seems redundant. However, logistic regression showed that activating KIR genotypes do influence the overall hierarchy of protection/susceptibility as reflected by composite inhibitory and activating KIR-HLA genotype models.
Assuntos
Diabetes Mellitus Tipo 1/genética , Antígenos HLA/genética , Modelos Biológicos , Receptores Imunológicos/genética , Adolescente , Estudos de Casos e Controles , Genótipo , Humanos , Células Matadoras Naturais/imunologia , Receptores Imunológicos/imunologia , Receptores KIRRESUMO
The extended major histocompatibility complex (xMHC) has been studied intensively with regard to type 1 diabetes (T1D) predisposition. So far, little attention has been given to the subregion centromeric of MHC class II. We selected five single nucleotide polymorphisms in genes with potential immune-related functions in the genomic regions of death-domain-associated protein 6 (DAXX, apoptosis associated), TAP-binding protein (TAPBP, human leukocyte antigen class I loading) and retinoic acid receptor beta (RXRB, vitamin D receptor function) that may bear relevance to the pathogenesis of T1D. A total of 277 unrelated individuals with juvenile-onset T1D and 286 control subjects were genotyped using sequence-specific priming-polymerase chain reaction. The genotype and allelic frequencies of the markers tested were not significantly different between patients and control subjects. Subsequent haplotype analysis showed six DAXX-TAPBP-RXRB haplotypic configurations. No difference was observed between patients and control cohorts when stratified for T1D high-risk DQ2-DR17 and DQ8-DR4 haplotypes. However, the distribution of these haplotypes affected T1D susceptibility encoded by the intermediate risk haplotypes DQ5-DR1 and DQ2-DR7 by increasing and decreasing susceptibility, respectively. We propose that studying genetic variants in the xMHC may be particularly rewarding to define disease pathways in patients displaying intermediate risk DQ-DR haplotypes.
Assuntos
Diabetes Mellitus Tipo 1/genética , Diabetes Mellitus Tipo 1/imunologia , Antígenos de Histocompatibilidade Classe II/biossíntese , Complexo Principal de Histocompatibilidade , Análise de Sequência de DNA , Alelos , Estudos de Casos e Controles , Frequência do Gene , Predisposição Genética para Doença , Variação Genética , Antígenos HLA , Haplótipos , Humanos , Desequilíbrio de Ligação , Receptores do Ácido Retinoico/metabolismo , RiscoRESUMO
We studied whether serum interferon (IFN)-gamma or interleukin (IL)-10 levels and their corresponding functional polymorphic genotypes are associated with partial remission of type 1 diabetes (T1D). A multi-centre study was undertaken in patients with newly diagnosed T1D and matched controls. T1D patients were followed for 3 months and characterized for remission status. Partial clinical remission was defined as a daily insulin dose Assuntos
Diabetes Mellitus Tipo 1/genética
, Diabetes Mellitus Tipo 1/imunologia
, Interferon gama/genética
, Interleucina-10/genética
, Análise de Variância
, Biomarcadores/sangue
, Estudos de Casos e Controles
, Distribuição de Qui-Quadrado
, Predisposição Genética para Doença
, Genótipo
, Humanos
, Interferon gama/sangue
, Interleucina-10/sangue
, Remissão Espontânea
, Tamanho da Amostra
RESUMO
Whether autoimmune mechanisms play a role in the pathogenesis of inclusion body myositis (IBM) is unknown. Human leukocyte antigen (HLA) analysis in 52 patients, including 17 with autoimmune disorders (AIDs), showed that patients were more likely to have antigens from the autoimmune-prone HLA-B8-DR3 ancestral haplotype than healthy control subjects, irrespective of the presence of AIDs. Patients lacked the apparently protective HLA-DR53 antigen. The results provide further support for an autoimmune basis in IBM.
Assuntos
Doenças Autoimunes/epidemiologia , Genes MHC da Classe II , Genes MHC Classe I , Antígenos HLA/análise , Antígenos HLA-D/análise , Miosite de Corpos de Inclusão/epidemiologia , Idade de Início , Idoso , Idoso de 80 Anos ou mais , Doenças Autoimunes/genética , Doenças Autoimunes/imunologia , Comorbidade , Feminino , Frequência do Gene , Predisposição Genética para Doença , Antígenos HLA/genética , Antígenos HLA/imunologia , Antígenos HLA-D/genética , Antígenos HLA-D/imunologia , Antígenos HLA-DR/análise , Antígenos HLA-DR/genética , Antígenos HLA-DR/imunologia , Cadeias HLA-DRB4 , Haplótipos/genética , Humanos , Masculino , Pessoa de Meia-Idade , Miosite de Corpos de Inclusão/genética , Miosite de Corpos de Inclusão/imunologia , Países Baixos/epidemiologia , PrevalênciaRESUMO
Insulin-like growth factor 1 (IGF1) plays an important role in the development and function of pancreatic beta-cells and contributes to infant growth, which we recently reported to be associated with type 1 diabetes (T1D). Here, we studied an IGF1 microsatellite in 206 families with T1D and its interaction with the polymorphism near the insulin (INS) gene variable number of tandem repeats. The IGF1 microsatellite was associated with T1D (P = 0.045), which was mainly caused by a protective effect of the 194 bp allele (36% transmission to affected offspring). Interestingly, co-segregation of this IGF1 194 bp allele affected the risk of INS alleles. These results provide the first evidence for an association of IGF1 with T1D and imply that co-inheritance of these functional genetic variants of IGF1 and insulin predispose to T1D.
Assuntos
Diabetes Mellitus Tipo 1/genética , Fator de Crescimento Insulin-Like I/genética , Insulina/genética , Repetições Minissatélites , Regiões Promotoras Genéticas , Mapeamento Cromossômico , Predisposição Genética para Doença , HumanosRESUMO
Alleles of HLA class II genes DQB1, DQA1, and DRB1 in the MHC region are major determinants of genetic predisposition to type 1 diabetes (T1D). Several alleles of each of these three loci are associated with susceptibility or protection from disease. In addition, relative risks for some DR-DQ genotypes are not simply the sum or product of the single haplotype relative risks. For example, the risk of the DRB1*03-DQB1*02/DRB1*0401-DQB1*0302 genotype is often found to be higher than for the individual DRB1*03-DQB1*02 and DRB1*0401-DQB1*0302 homozygous genotypes. It has been hypothesized that this synergy or epistasis occurs through formation of highly susceptible trans-encoded HLA-DQ(alpha 1, beta 1) heterodimers. Here, we evaluated this hypothesis by estimating the disease associations of the range of DR-DQ genotypes and their inferred dimers in a large collection of nuclear families. We determined whether the risk of haplotypes in DRB1*0401-DQB1*0302-positive genotypes relative to the DRB1*03-DQB1*02-positive genotypes is different from that of DRB1*01-DQB1*0501, which we used as a baseline reference. Several haplotypes showed a different risk compared to DRB1*01-DQB1*0501, which correlated with their ability to form certain trans-encoded DQ dimers. This result provides new evidence for the potential importance of trans-encoded HLA DQ molecules in the determination of HLA-associated risk in T1D.
Assuntos
Diabetes Mellitus Tipo 1/genética , Epistasia Genética , Antígenos HLA-DQ/genética , Antígenos HLA-DR/genética , Estudos de Casos e Controles , Diabetes Mellitus Tipo 1/etnologia , Dimerização , Feminino , Frequência do Gene/genética , Predisposição Genética para Doença/genética , Genótipo , Antígenos HLA-DQ/metabolismo , Cadeias beta de HLA-DQ , Antígenos HLA-DR/metabolismo , Cadeias HLA-DRB1 , Haplótipos/genética , Humanos , Masculino , Risco , População Branca/genéticaRESUMO
Genetic association with type 1 diabetes (T1D) has been established for two chromosomal regions: HLA DQ/DR (IDDM1) and INS VNTR (IDDM2). To identify additional genetic markers, we tested polymorphisms in regulatory regions of several cytokine and important metabolic genes. These polymorphisms exhibit functional consequences for expression and function. Functional genetic polymorphisms of proinflammatory (T-helper-1: IL-2, IL-12 and IFN-gamma), anti-inflammatory (T-helper-2: IL-4, IL-6 and IL-10) and metabolic (IGF-I, VDR and INS) genes were determined in 206 Dutch simplex families with juvenile onset T1D and the results were analysed using the transmission disequilibrium test. Significantly increased transmission to T1D probands was observed for the loci IDDM1, IDDM2 and the vitamin D receptor. Although none of the other individual polymorphisms was associated with disease individually, the combination of T-helper-2 and metabolic/growth alleles IL-10(*)R2, IL-4(*)C, VDR(*)C and IGF-I(*)wt was found to be transmitted more frequently than expected (67%, P(c)=0.015). We conclude that additional genetic predisposition to T1D is defined by combinations of markers (eg Th2 and metabolic) rather than by a single marker. The consequences of the increased transmission of a low Th2 expressing genotypes together with a normal Th1 profile may result in a net proinflammatory cytokine expression pattern.
Assuntos
Citocinas/genética , Diabetes Mellitus Tipo 1/genética , Predisposição Genética para Doença/genética , Metabolismo/genética , Polimorfismo Genético , Adolescente , Criança , Pré-Escolar , Feminino , Frequência do Gene , Marcadores Genéticos , Testes Genéticos , Antígenos HLA-DR/genética , Humanos , MasculinoRESUMO
Our aim was to examine, using microsatellite (ms) markers, the contribution of the telomeric part of the HLA region to rheumatoid arthritis (RA) predisposition in the Spanish population. We have looked at the distribution of DQB1, DRBI and five ms loci (D6S1014, D6S273, D6STNFa, MIB and C1-2-5) within the HLA region in 147 Spanish RA patients and 202 control subjects. A total of 19 conserved ms configurations were observed, twelve of them in linkage disequilibrium with particular DQB1-DRB1 haplotypes. Interestingly, haplotype c1 (DQB1*0201-DRB1*0301-D6S1014*143-D6S273*139-D6STNFa*99-MIB*350-C1-2-5*196) was significantly associated with RA predisposition. As part of this haplotype, the MIB*350 allele was found to be a risk factor independently of the RA-predisposing haplotypes. The present results along with data from others prove the existence of a second predisposing locus located inside the MHC region, and suggest that might be located within the TNFa-HLA-B region.
Assuntos
Artrite Reumatoide/genética , Artrite Reumatoide/imunologia , Predisposição Genética para Doença , Antígenos HLA/genética , Artrite Reumatoide/epidemiologia , Linhagem Celular Transformada , Genes MHC da Classe II/genética , Antígenos HLA/classificação , Haplótipos , Humanos , Repetições de Microssatélites/genética , Epidemiologia Molecular , Fenótipo , Reação em Cadeia da Polimerase , Polimorfismo Genético , Análise de Sequência de DNA , Espanha/epidemiologia , Telômero/genética , Telômero/imunologiaRESUMO
BACKGROUND: Human leukocyte antigen (HLA)-DR2 carriership is associated with an increased risk for MS. Genome searches using microsatellite markers have consistently shown that additional genetic factors contribute to susceptibility for MS. OBJECTIVE: To identify loci within the HLA region that predispose to relapse-onset MS independently of HLA-DR2. METHOD: A case-control study involving 159 patients with definite relapse-onset MS and 273 control subjects was conducted. Six highly polymorphic microsatellite markers encoded within the HLA-C to DR region, that is, D6S1014, D6S273, TNFa, MIB, C1_2_5, and C1_3_2, three single-nucleotide tumor necrosis factor (TNF) promoter gene polymorphisms at positions -238, -308, and -376, and HLA-DR2 carriership were typed. RESULTS: These data confirmed the well-known association between the HLA-DR2 haplotype and relapse-onset MS, yielding an odds ratio (OR) of 3.6 (95% CI: 2.4 to 5.4; p < 0.0001). Multivariate analyses revealed that C1_3_2*354 was also associated with an increased risk for developing relapse-onset MS independently of HLA-DR2 (OR: 2.0; 95% CI: 1.2 to 3.1; p = 0.004). This allele is encoded within an ancestral haplotype that is highly linked to HLA-DR3. The joint effect of this ancestral haplotype and HLA-DR2 resulted in an OR of 8.7 (95% CI: 2.7 to 29; p < 0.0001) to develop relapse-onset MS. In addition, a protective risk factor was found: carriers of TNFa*107 had a 0.5-fold lower risk to develop relapse-onset MS (95% CI: 0.3 to 0.9; p = 0.026). CONCLUSION: Within the HLA region, other loci besides HLA-DR2 haplotype modulate susceptibility for relapse-onset MS.
Assuntos
Predisposição Genética para Doença , Antígeno HLA-DR2/genética , Esclerose Múltipla Recidivante-Remitente/genética , Adulto , Alelos , Estudos de Casos e Controles , Feminino , Dosagem de Genes , Ligação Genética , Testes Genéticos , Antígeno HLA-DR3/genética , Haplótipos , Heterozigoto , Teste de Histocompatibilidade , Humanos , Masculino , Repetições de Microssatélites/genética , Pessoa de Meia-Idade , Esclerose Múltipla Recidivante-Remitente/epidemiologia , Análise Multivariada , Países Baixos/epidemiologia , Razão de Chances , Regiões Promotoras Genéticas/genética , Medição de Risco , Fatores de Risco , Fator de Necrose Tumoral alfa/genéticaAssuntos
Diabetes Mellitus Tipo 1/genética , Diabetes Mellitus Tipo 1/imunologia , Antígenos HLA-D/genética , Repetições de Microssatélites , Pareamento de Bases , Frequência do Gene , Antígenos HLA-DQ/genética , Cadeias alfa de HLA-DQ , Cadeias beta de HLA-DQ , Haplótipos , Humanos , Países Baixos , Fator de Necrose Tumoral alfa/genéticaRESUMO
Differences in allelic distribution at loci surrounding the human HLA-DRB1 and tumor necrosis factor (TNF) genes have been observed in association with systemic lupus erythematosus (SLE). We investigated whether the association of HLA-DRB1*0301 (HLA-DR3) and TNF-308A with SLE could be attributed to polymorphic markers in the chromosomal region encompassed by HLA-DRB1 and HLA-C. Ninety-one consecutive Caucasian patients with SLE and 253 controls (organ donors) were typed for HLA-DRB1, microsatellites D6S1014, D6S273, TNFa, MIB, C1_2_5, and C1_3_2 and the single nucleotide polymorphism at position -308 in the promoter of TNF. The independent contribution of alleles to disease susceptibility was estimated by cross-tabulation and multivariate logistic regression. Possession of TNF-308A was associated with susceptibility to SLE (odds ratio [95% confidence interval], 3.70 [2.24-6.11]). This remained present after stratification on possession of HLA-DR3 (pooled odds ratio, 2.53 [1.37-4.70]). Stratification revealed a possible association of possession of C1_2_5*192 with protection from SLE beyond the effects of HLA-DR3 and TNF-308A. A gene dosage effect was observed for -308A only (homozygotes, 7.75 [3.01-20.0], heterozygotes, 3.15 [1.85-5.37]). In multivariate analysis, possession of HLA-DR3, TNF-308A, and C1_2_5*192 remained independently associated with susceptibility to SLE (2.58 [1.29-5.18], 2.76 [1.43-5.31], and 0.26 [0.10-0.66], respectively). The association of possession of TNF-308A with susceptibility to SLE cannot be attributed to linkage to HLA-DR3 alone, nor to other polymorphic markers in the vicinity of the TNF gene. Further loci that are independently associated with SLE might be in the vicinity of marker C1_2_5.
Assuntos
Cromossomos Humanos Par 6/genética , Antígeno HLA-DR3/genética , Lúpus Eritematoso Sistêmico/genética , Repetições de Microssatélites/genética , Mapeamento Físico do Cromossomo , Fator de Necrose Tumoral alfa/genética , Adulto , Feminino , Frequência do Gene/genética , Predisposição Genética para Doença/genética , Antígenos HLA-DR/genética , Cadeias HLA-DRB1 , Humanos , Masculino , Análise Multivariada , Razão de Chances , Reação em Cadeia da Polimerase , Polimorfismo Genético/genética , População Branca/genéticaRESUMO
We established the detailed polymorphism of the 5'-flanking region and the first exon of the human leukocyte antigen (HLA)-DQB1 alleles. One hundred and forty-five Spanish rheumatoid arthritis (RA) patients and 200 healthy voluntary blood donors from southern Spain along with 42 B-cell lines were analyzed for the presence of the retrovirus-derived long terminal repeats (LTRs) LTR3, LTR5, and LTR13. LTR3 positivity was always associated with certain DQB1 alleles, i.e., *0302, *0402, *0601, *0202, and *0305. Sequencing analysis of the 5'-flanking region of DQB1*0301, *0303 and *0502 alleles in homozygous B-cell lines showed the absence of LTR3 and a massive deletion of 5635 base pairs. The undetected deletion in the flanking region of some DQB1 alleles and a lack of stratification for HLA typing explain previously reported associations of the LTR3 element with RA and type I diabetes (IDDM). LTR5 showed identical distribution to LTR3, consistent with a previously suggested LTR3-LTR5 tandem arrangement. LTR13 positivity was associated with DQB1*0302, *0303, and *0402 alleles. Distributions of the LTR elements in all B-cell lines, RA patients, and controls could be explained entirely by linkage disequilibrium with DQB1 alleles, independently of the haplotypes carrying them. LTR elements are known to regulate gene expression. Therefore, a possible involvement of LTR13 in the association of DQB1*0302, *0303, and *0402 with IDDM requires further investigation. The sequencing results of the DQB1 first exon demonstrated that DQB1*0601 was generated by a recombination event between a DR53 and a non-DR53 haplotype. Our results shed new light on the phylogeny of the HLA region and the possible contribution of DQB1 to susceptibility to autoimmunity.
Assuntos
Autoimunidade/genética , Retrovirus Endógenos/genética , Antígenos HLA-DQ/genética , Sequências Repetidas Terminais , Alelos , Artrite Reumatoide/genética , Artrite Reumatoide/imunologia , Linfócitos B/imunologia , Sequência de Bases , Estudos de Casos e Controles , Linhagem Celular , Primers do DNA/genética , Diabetes Mellitus Tipo 1/genética , Diabetes Mellitus Tipo 1/imunologia , Éxons , Cadeias beta de HLA-DQ , Humanos , Polimorfismo Genético , EspanhaRESUMO
We have evaluated the possible contribution of genes besides DQ and DR to the association of HLA with rheumatoid arthritis (RA). To this end, we have looked at the allele distributions of six microsatellites, D6S1014, D6S2673, TNFalpha, MIB, C1-2-5, and C1-3-2 among 132 RA patients and 254 controls. We have defined 19 microsatellite clusters corresponding to previously described ancestral haplotypes. One of them was D6S1014*143-D6S273*139-TNFalpha*99-MIB*350-C1-2-5*196-C1-3-2*354, often found associated with DQB1*0201-DRB1*0301. As part of this microsatellite cluster, the allele MIB*350 was found to be a RA-predisposing factor, independent of DRB1*0301 and RA-predisposing haplotypes DQB1*03-DRB1*04 and DQB1*0501-DRB1*01. We conclude that the telomeric part of the HLA region contains a locus conferring predisposition to RA independently of HLA class II.
Assuntos
Artrite Reumatoide/genética , Artrite Reumatoide/imunologia , Genes MHC da Classe II , Predisposição Genética para Doença/genética , Antígenos HLA/genética , Telômero/genética , Telômero/imunologia , Antígenos HLA-D/genética , Humanos , Repetições de Microssatélites/genética , Repetições de Microssatélites/imunologiaRESUMO
The microsatellite locus TNFa is frequently used as an additional genetic marker in studies of the major histocompatibility complex (MHC). Novel sequence variations at the TNFa locus have been described, and which may have implications for genetic analyses. In this study, we set up a nested polymerase chain reaction-sequence-specific primer (PCR-SSP) approach to type for these TNFa sequence variations. First, sequencing analysis of workshop B lymphoblastoid cell lines (n=13) showed the presence of three sequence variations upstream of the dinucleotide repeat at TNFa. Using nested PCR-SSP, we were able to detect these variations in a larger B lymphoblastoid cell line panel (n=34). Furthermore, we were able to show that TNFa alleles a7 and a10 are present in two distinct conformations leading to "splitting" of TNFa alleles exhibiting identical fragment lengths. To establish the frequency of the TNFa alleles and their variants, we performed microsatellite typing of a large panel of random individuals from the Dutch population (n=272). Subsequent nested PCR-SSP typing showed the presence of three previously described sequence variations in the Dutch population. Furthermore, the presence of a fourth subtype was established. The described variations of allele TNFa7 and TNFa10 are present in the random population with significant frequencies. Haplotyping analysis between HLA-DR, TNFa, and HLA-B showed that allele TNFa7.2 is present in an extended DR7-TNFa7.2-B13 haplotype. In this way, we were able to show that the additional sequence variations behave like distinct TNFa alleles.
Assuntos
Variação Genética , Fator de Necrose Tumoral alfa/genética , Linhagem Celular , Haplótipos , Humanos , Repetições de Microssatélites , Reação em Cadeia da Polimerase/métodos , Fator de Necrose Tumoral alfa/classificaçãoRESUMO
The nature and frequency of human histocompatibility leukocyte antigen (HLA) class I loss mechanisms in primary cancers are largely unknown. We used flow cytometry and molecular analyses to concurrently assess allele-specific HLA phenotypes and genotypes in subpopulations from 30 freshly isolated cervical tumor cell suspensions.Tumor-associated HLA class I alterations were present in 90% of the lesions tested, comprising four altered pheno/genotype categories: (a) HLA-A or -B allelic loss (17%), mostly associated with gene mutations; (b) HLA haplotype loss, associated with loss of heterozygosity at 6p (50%). This category included cases with additional loss of a (third) HLA-A or -B allele due to mutation, as well as one case with an HLA class I-negative tumor cell subpopulation, caused by a beta2-microglobulin gene mutation; (c) Total HLA class I antigen loss and retention of heterozygosity (ROH) at 6p (10%); and (d) B locus or HLA-A/B downregulation associated with ROH and/or allelic imbalance at 6p (10%). Normal HLA phenotypes and ROH at 6p were observed in 10% of the cases. One case could not be classified (3%). Altered HLA class I antigen expression occurs in most cervical cancers, is diverse, and is mainly caused by genetic changes. Combined with widespread tumor heterogeneity, these changes have profound implications for natural immunity and T cell-based immunotherapy in cervical cancer.
Assuntos
Deleção de Genes , Antígenos HLA-A/genética , Antígenos HLA-B/genética , Neoplasias do Colo do Útero/genética , Neoplasias do Colo do Útero/imunologia , Adenocarcinoma/química , Adenocarcinoma/genética , Adenocarcinoma/imunologia , Carcinoma de Células Escamosas/química , Carcinoma de Células Escamosas/genética , Carcinoma de Células Escamosas/imunologia , Cromossomos Humanos Par 6/genética , Análise Mutacional de DNA , Feminino , Citometria de Fluxo , Genótipo , Haplótipos , Humanos , Imuno-Histoquímica , Repetições de Microssatélites/genética , Fenótipo , Reação em Cadeia da Polimerase , Neoplasias do Colo do Útero/químicaRESUMO
Lack of expression of HLA class I antigens is frequently observed on primary uveal melanoma, and is correlated with improved patient survival. Several mechanisms may contribute to the observed loss of HLA class I expression, including changes at the DNA level. In this study, we used microsatellite analysis as a molecular genetic approach to examine loci on chromosome 6p for loss of heterozygosity (LOH). Three pairs of microsatellite markers were used to screen 20 formalin-fixed, paraffin-embedded uveal melanomas for LOH on the short arm of chromosome 6. In all cases, normal adjacent scleral tissue was used as a control. We identified LOH in eleven cases from microsatellite locus D6S105 to the telomere, in eight cases from microsatellite locus D6STNFa to the telomere (area includes D6S105), and in seven cases from microsatellite locus D6S291 to the end of chromosome 6p (includes D6STNFa and D6S105). In seven cases, retention of heterozygosity was found at all three loci using these primers. Our results suggest that loss of heterozygosity on chromosome 6p is a common feature in uveal melanoma. We did not find a correlation between the presence of LOH and locus-specific HLA-A and -B expression.
Assuntos
Cromossomos Humanos Par 6/genética , Perda de Heterozigosidade , Melanoma/genética , Neoplasias Uveais/genética , Neoplasias da Coroide/genética , Neoplasias da Coroide/imunologia , Neoplasias da Coroide/cirurgia , Corpo Ciliar/patologia , Enucleação Ocular , Antígenos HLA-A , Antígenos HLA-B , Humanos , Melanoma/imunologia , Melanoma/cirurgia , Repetições de Microssatélites , Reação em Cadeia da Polimerase , Neoplasias Uveais/imunologia , Neoplasias Uveais/cirurgiaRESUMO
BACKGROUND: Various mechanisms contribute to the loss of human leukocyte antigen (HLA) class I expression that is frequently observed in cancers. Although some single allele losses have been ascribed to mutations in HLA class I genes, direct evidence for this phenomenon in vivo is still lacking. Thus, we investigated whether HLA class I gene mutations could account for the loss of allele-specific expression in cervical carcinomas. METHODS: We used polymerase chain reaction-based techniques, including sequencing, oligonucleotide hybridization, and microsatellite analysis, to identify HLA class I gene defects in two tumor-derived cell lines and to confirm the presence of these defects in the original tumors. RESULTS: In one tumor, in exon 2 of the HLA-B15 gene, a four-nucleotide insertion resulted in a stop codon in exon 3. In the other tumor, in two duplicated copies of the HLA-A24 gene, single-point mutations resulted in stop codons in exons 2 and 5. CONCLUSIONS: To our knowledge, this is the first report of HLA class I gene mutations identified in primary tumors that lead to loss of allelic expression in tumor cells. Such tumor-specific mutations may permit the cell to escape HLA class I-restricted cytotoxic T-cell responses.
Assuntos
Genes MHC Classe I/genética , Mutação , Neoplasias do Colo do Útero/genética , Cromossomos Humanos Par 6/genética , Primers do DNA , Feminino , Genótipo , Humanos , Fenótipo , Reação em Cadeia da Polimerase/métodos , Células Tumorais CultivadasRESUMO
Polymorphism at the level of two microsatellite loci (D6S273 and TNFa) was studied in Croatian population. The most frequent alleles at D6S273 locus are D6S273 134 bp and 136 bp, while at TNFa locus two most frequent alleles are TNFa 117 bp and 99 bp. This study confirms the irregularity in distribution of microsatellite alleles in different populations with the predominance of two or three alleles on these two investigated microsatellite loci.
Assuntos
Alelos , Frequência do Gene , Complexo Principal de Histocompatibilidade/genética , Repetições de Microssatélites/genética , Fator de Necrose Tumoral alfa/genética , Croácia , Humanos , Polimorfismo GenéticoRESUMO
Loss of heterozygosity (LOH) contributes significantly to the inactivation of tumor suppressor genes and may involve a variety of mechanisms. Studying loss of HLA-A2 alleles in human lymphoblastoid cell lines, we previously showed that mitotic recombination and chromosome loss with concomitant duplication of the non-selected chromosome were the most frequent mechanisms of LOH. In the present study we used the HLA system to determine the rate and spectrum of LOH mutations in the EBV transformed lymphoblastoid cell line R83-4915. Spontaneous loss of HLA-A2 in R83-4915 occurred with a rate of 7.9x10-7 which was 5 to 10-times lower compared to the previously observed rate of loss of HLA-A2 in other lymphoblastoid cell lines. Among the HLA-A2 mutants, 27% did not show LOH of additional chromosome 6 markers. Molecular analysis showed that neither large deletion nor gene conversion was the cause for their mutant phenotype. The remaining mutants showed LOH, which was caused by mitotic recombination (40%) and chromosome loss (33%). However, the chromosome loss observed in mutants of R83-4915 was not accompanied by the duplication of the remaining chromosome. Instead 3 out of 5 mutants became polyploid suggesting that different mechanisms exist to compensate for chromosome loss. In conclusion, the rate and types of LOH that can be observed in cell lines obtained from various donors may depend on the genetic make-up or the transformation status of these cells
Assuntos
Perda de Heterozigosidade/genética , Linfócitos/metabolismo , Idoso , Idoso de 80 Anos ou mais , Linhagem Celular Transformada , Células Cultivadas , Deleção Cromossômica , Células Clonais , DNA/análise , Antígeno HLA-A2/genética , Humanos , Hibridização in Situ Fluorescente , Linfócitos/química , Linfócitos/imunologiaRESUMO
We analyzed the HLA-A, -B, -DR and -DQ phenotypes and 12 microsatellite locus genotypes within and close to the major histocompatibility complex in a panel of 98 randomly selected, healthy, unrelated Dutch Caucasoid individuals. Allele frequencies and Hardy-Weinberg equilibrium (HWE) were calculated. Also, the linkage disequilibrium patterns between HLA and microsatellite loci were studied. The HLA-A, -B, -DR, -DQ and six microsatellite loci centromeric of the HLA-A showed HWE. In contrast, all microsatellites telomeric of the HLA-A showed deviation from HWE due to excess of homozygosity. Linkage disequilibrium analyses provided strong evidence that among the tested microsatellite loci only the alleles of the D6STNFa locus are in linkage disequilibrium with both HLA-B and -DR. Our results suggest that selection acting on the HLA genes includes the D6STNFa locus and linked genes.