Dataset Information

HLA-A and -B alleles and haplotypes in hemochromatosis probands with HFE C282Y homozygosity in central Alabama.

ABSTRACT: BACKGROUND:We wanted to quantify HLA-A and -B allele and haplotype frequencies in Alabama hemochromatosis probands with HFE C282Y homozygosity and controls, and to compare results to those in other populations. METHODS:Alleles were detected using DNA-based typing (probands) and microlymphocytotoxicity (controls). RESULTS:Alleles were determined in 139 probands (1,321 controls) and haplotypes in 118 probands (605 controls). In probands, A*03 positivity was 0.7482 (0.2739 controls; p = or < 0.0001; odds ratio (OR) 7.9); positivity for B*07, B*14, and B*56 was also increased. In probands, haplotypes A*03-B*07 and A*03-B*14 were more frequent (p < 0.0001, respectively; OR = 12.3 and 11.1, respectively). The haplotypes A*01-B*60, A*02-B*39, A*02-B*62, A*03-B*13, A*03-B*15, A*03-B*27, A*03-B*35, A*03-B*44, A*03-B*47, and A*03-B*57 were also significantly more frequent in probands. 37.3% of probands were HLA-haploidentical with other proband(s). CONCLUSIONS:A*03 and A*03-B*07 frequencies are increased in Alabama probands, as in other hemochromatosis cohorts. Increased absolute frequencies of A*03-B*35 have been reported only in the present Alabama probands and in hemochromatosis patients in Italy. Increased absolute frequencies of A*01-B*60, A*02-B*39, A*02-B*62, A*03-B*13, A*03-B*15, A*03-B*27, A*03-B*44, A*03-B*47, and A*03-B*57 in hemochromatosis cohorts have not been reported previously.

SUBMITTER: Barton JC

PROVIDER: S-EPMC137582 | biostudies-literature | 2002 Oct

REPOSITORIES: biostudies-literature

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HLA-A and -B alleles and haplotypes in hemochromatosis probands with HFE C282Y homozygosity in central Alabama.

Barton James C JC Acton Ronald T RT

BMC medical genetics 20021007

<h4>Background</h4>We wanted to quantify HLA-A and -B allele and haplotype frequencies in Alabama hemochromatosis probands with HFE C282Y homozygosity and controls, and to compare results to those in other populations.<h4>Methods</h4>Alleles were detected using DNA-based typing (probands) and microlymphocytotoxicity (controls).<h4>Results</h4>Alleles were determined in 139 probands (1,321 controls) and haplotypes in 118 probands (605 controls). In probands, A*03 positivity was 0.7482 (0.2739 con ...[more]

PMID: 12370085

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Project description:ImportanceHereditary hemochromatosis is predominantly caused by the HFE p.C282Y homozygous pathogenic variant. Liver carcinoma and mortality risks are increased in individuals with clinically diagnosed hereditary hemochromatosis, but risks are unclear in mostly undiagnosed p.C282Y homozygotes identified in community genotyping.ObjectiveTo estimate the incidence of primary hepatic carcinoma and death by HFE variant status.Design, setting, and participantsCohort study of 451 186 UK Biobank participants of European ancestry (aged 40-70 years), followed up from baseline assessment (2006-2010) until January 2018.ExposuresMen and women with HFE p.C282Y and p.H63D genotypes compared with those with neither HFE variants.Main outcomes and measuresTwo linked co-primary outcomes (incident primary liver carcinoma and death from any cause) were ascertained from follow-up via hospital inpatient records, national cancer registry, and death certificate records, and from primary care data among a subset of participants for whom data were available. Associations between genotype and outcomes were tested using Cox regression adjusted for age, assessment center, genotyping array, and population genetics substructure. Kaplan-Meier lifetable probabilities of incident diagnoses were estimated from age 40 to 75 years by HFE genotype and sex.ResultsA total of 451 186 participants (mean [SD] age, 56.8 [8.0] years; 54.3% women) were followed up for a median (interquartile range) of 8.9 (8.3-9.5) years. Among the 1294 male p.C282Y homozygotes, there were 21 incident hepatic malignancies, 10 of which were in participants without a diagnosis of hemochromatosis at baseline. p.C282Y homozygous men had a higher risk of hepatic malignancies (hazard ratio [HR], 10.5 [95% CI, 6.6-16.7]; P < .001) and all-cause mortality (n = 88; HR, 1.2 [95% CI, 1.0-1.5]; P = .046) compared with men with neither HFE variant. In lifetables projections for male p.C282Y homozygotes to age 75 years, the risk of primary hepatic malignancy was 7.2% (95% CI, 3.9%-13.1%), compared with 0.6% (95% CI, 0.4%-0.7%) for men with neither variant, and the risk of death was 19.5% (95% CI, 15.8%-24.0%), compared with 15.1% (95% CI, 14.7%-15.5%) among men with neither variant. Among female p.C282Y homozygotes (n = 1596), there were 3 incident hepatic malignancies and 60 deaths, but the associations between homozygosity and hepatic malignancy (HR, 2.1 [95% CI, 0.7-6.5]; P = .22) and death (HR, 1.2 [95% CI, 0.9-1.5]; P = .20) were not statistically significant.Conclusions and relevanceAmong men with HFE p.C282Y homozygosity, there was a significantly increased risk of incident primary hepatic malignancy and death compared with men without p.C282Y or p.H63D variants; there was not a significant association for women. Further research is needed to understand the effects of early diagnosis and treatment.

Project description:It has been recently demonstrated that CD8+ T-lymphocyte numbers are genetically transmitted in association with the MHC class I region. The present study was designed with the objective of narrowing the region associated with the setting of CD8+ T-lymphocyte numbers in a population of C282Y homozygous hemochromatosis subjects, in whom a high prevalence of abnormally low CD8+ T-lymphocyte counts has been described.The study includes 43 C282Y homozygous subjects fully characterized both phenotypically and genotypically. Clinical characterization includes measurements of iron parameters at diagnosis (transferrin saturation and serum ferritin), total body iron stores and T-cell immunophenotyping determined by flow cytometry. Genetic characterization includes HLA class I alleles (A, B and C) and four additional microsatellite markers (D6S265, D6S2222, D6S105 and D6S2239) spanning 5 Megabases in the 6p21.3 region.Eighty-two extended C282Y carrying haplotypes were defined. Single-locus analysis revealed that the HLA-A region was associated with CD8+ T-cell numbers. Multivariate analysis showed that the combinations of the most common HLA-A alleles (HLA-A*03, -A*02 and -A*01) were associated with significantly lower numbers of CD8+ T-lymphocytes (0.30 +/- 0.14 x 106/ml), in comparison with subjects carrying only one copy of those alleles (0.46 +/- 0.19 x 106/ml) and subjects without any copy of those alleles (0.79 +/- 0.15 x 106/ml;p = 0.0001). No differences were observed in CD8+ T-cell counts among control subjects carrying the same combinations of HLA-A alleles (0.47 +/- 0.14; 0.45 +/- 0.21 and 0.41 +/- 0.17 x 106/ml, respectively), therefore not supporting a direct effect of HLA specificity but rather an indirect association with a locus close to HLA-A. Multivariate analysis showed that the combination of the most common HLA-A alleles also have an impact on the clinical expression of HH in terms of iron stores, in males(p = 0.0009).The present study provides evidence supporting an inextricable link between extended HLA haplotypes, CD8+ T-lymphocyte numbers and severity of iron overload in hereditary hemochromatosis(HH). It gives additional information to better define a candidate region involved in the regulation of CD8+ T-lymphocyte numbers. A new evolutionary hypothesis concerning the inheritance of the phenotype of low CD8+ T-lymphocyte numbers associated with particular ancestral HLA haplotypes carrying the C282Y mutation and its implication on the clinical heterogeneity of HH is discussed.

Project description:BackgroundIn hemochromatosis, causes of abdominal pain and its associations with cirrhosis are poorly understood.MethodsWe retrospectively compared characteristics of referred hemochromatosis probands with HFE p.C282Y homozygosity with/without biopsy-proven cirrhosis: sex, age, diabetes, heavy alcohol consumption, abdominal pain/tenderness, hepatomegaly, splenomegaly, non-alcoholic fatty liver disease, chronic viral hepatitis, ascites, transferrin saturation (TS), serum ferritin (SF), and iron removed by phlebotomy (QFe). We performed logistic regression on cirrhosis using characteristics identified in univariate comparisons. We performed computerized and manual searches to identify hemochromatosis case series and compiled prevalence data on cirrhosis and abdominal pain and causes of abdominal pain.ResultsOf 219 probands, 57.1% were men. Mean age was 48±13 y. In 22 probands with cirrhosis, proportions of men, mean age, prevalences of heavy alcohol consumption, abdominal pain, abdominal tenderness, hepatomegaly, splenomegaly, and chronic viral hepatitis, and median TS, SF, and QFe were significantly greater than in probands without cirrhosis. Regression analysis revealed three associations with cirrhosis: abdominal pain (p = 0.0292; odds ratio 9.8 (95% CI: 1.2, 76.9)); chronic viral hepatitis (p = 0.0153; 11.5 (95% CI: 1.6, 83.3)); and QFe (p = 0.0009; 1.2 (95% CI: 1.1, 1.3)). Of eight probands with abdominal pain, five had cirrhosis and four had diabetes. One proband each with abdominal pain had heavy alcohol consumption, chronic viral hepatitis B, hepatic sarcoidosis, hepatocellular carcinoma, and chronic cholecystitis, cholelithiasis, and sigmoid diverticulitis. Abdominal pain was alleviated after phlebotomy alone in four probands. In 12 previous reports (1935-2011), there was a negative correlation of cirrhosis prevalence and publication year (p = 0.0033). In 11 previous reports (1935-1996), a positive association of abdominal pain prevalence and publication year was not significant (p = 0.0802).ConclusionsAbdominal pain, chronic viral hepatitis, and QFe are significantly associated with cirrhosis in referred hemochromatosis probands with HFE p.C282Y homozygosity. Iron-related and non-iron-related factors contribute to the occurrence of abdominal pain.

Project description:Hereditary Hemochromatosis (HH) is a recessively inherited disorder of iron overload occurring commonly in subjects homozygous for the C282Y mutation in HFE gene localized on chromosome 6p21.3 in linkage disequilibrium with the human leukocyte antigen (HLA)-A locus. Although its genetic homogeneity, the phenotypic expression is variable suggesting the presence of modifying factors. One such genetic factor, a SNP microhaplotype named A-A-T, was recently found to be associated with a more severe phenotype and also with low CD8(+)T-lymphocyte numbers. The present study aimed to test whether the predictive value of the A-A-T microhaplotype remained in other population settings. In this study of 304 HH patients from 3 geographically distant populations (Porto, Portugal 65; Alabama, USA 57; Nord-Trøndelag, Norway 182), the extended haplotypes involving A-A-T were studied in 608 chromosomes and the CD8(+) T-lymphocyte numbers were determined in all subjects. Patients from Porto had a more severe phenotype than those from other settings. Patients with A-A-T seemed on average to have greater iron stores (p = 0.021), but significant differences were not confirmed in the 3 separate populations. Low CD8(+) T-lymphocytes were associated with HLA-A*03-A-A-T in Porto and Alabama patients but not in the greater series from Nord-Trøndelag. Although A-A-T may signal a more severe iron phenotype, this study was unable to prove such an association in all population settings, precluding its use as a universal predictive marker of iron overload in HH. Interestingly, the association between A-A-T and CD8(+) T-lymphocytes, which was confirmed in Porto and Alabama patients, was not observed in Nord-Trøndelag patients, showing that common HLA haplotypes like A*01-B*08 or A*03-B*07 segregating with HFE/C282Y in the three populations may carry different messages. These findings further strengthen the relevance of HH as a good disease model to search for novel candidate loci associated with the genetic transmission of CD8(+) T-lymphocyte numbers.

Dataset Information

HLA-A and -B alleles and haplotypes in hemochromatosis probands with HFE C282Y homozygosity in central Alabama.

Publications

HLA-A and -B alleles and haplotypes in hemochromatosis probands with HFE C282Y homozygosity in central Alabama.

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