Involvement of the major histocompatibility complex region in the genetic regulation of circulating CD8 T-cell numbers in humans

Increased Plasma Ferritin Concentration and Low-Grade Inflammation-A Mendelian Randomization Study

BACKGROUND

It is unknown why increased plasma ferritin concentration predicts all-cause mortality. As low-grade inflammation and increased plasma ferritin concentration are associated with all-cause mortality, we hypothesized that increased plasma ferritin concentration is genetically associated with low-grade inflammation.

METHODS

We investigated whether increased plasma ferritin concentration is associated with low-grade inflammation [i.e., increased concentrations of C-reactive protein (CRP) and complement component 3 (C3)] in 62537 individuals from the Danish general population. We also applied a Mendelian randomization approach, using the hemochromatosis genotype C282Y/C282Y as an instrument for increased plasma ferritin concentration, to assess causality.

RESULTS

For a doubling in plasma ferritin concentration, the odds ratio (95% CI) for CRP ≥2 vs <2 mg/L was 1.12 (1.09-1.16), with a corresponding genetic estimate for C282Y/C282Y of 1.03 (1.01-1.06). For a doubling in plasma ferritin concentration, odds ratio (95% CI) for complement C3 >1.04 vs ≤1.04 g/L was 1.28 (1.21-1.35), and the corresponding genetic estimate for C282Y/C282Y was 1.06 (1.03-1.12). Mediation analyses showed that 74% (95% CI, 24-123) of the association of C282Y/C282Y with risk of increased CRP and 56% (17%-96%) of the association of C282Y/C282Y with risk of increased complement C3 were mediated through plasma ferritin concentration.

CONCLUSIONS

Increased plasma ferritin concentration as a marker of increased iron concentration is associated observationally and genetically with low-grade inflammation, possibly indicating a causal relationship from increased ferritin to inflammation. However, as HFE may also play an immunological role indicating pleiotropy and as incomplete penetrance of C282Y/C282Y indicates buffering mechanisms, these weaknesses in the study design could bias the genetic estimates.

Effects of highly conserved major histocompatibility complex (MHC) extended haplotypes on iron and low CD8+ T lymphocyte phenotypes in HFE C282Y homozygous hemochromatosis patients from three geographically distant areas

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.

Lymphocyte subsets in alcoholic liver disease

AIM

To compare lymphocyte subsets between healthy controls and alcoholics with liver disease.

METHODS

The patient cohort for this study included individuals who were suspected to have alcoholic liver disease (ALD) and who had undergone liver biopsy (for disease grading and staging, doubts about diagnosis, or concurrent liver disease; n = 56). Normal controls included patients who were admitted for elective cholecystectomy due to non-complicated gallstones (n = 27). Formalin-fixed, paraffin-embedded liver biopsy specimens were sectioned and stained with hematoxylin and eosin and Perls' Prussian blue. The non-alcoholic steatohepatitis score was used to assess markers of ALD. Lymphocyte population subsets were determined by flow cytometry. T lymphocytes were identified (CD3(+)), and then further subdivided into CD4(+) or CD8(+) populations. B lymphocytes (CD19(+)) and natural killer (NK) cell numbers were also measured. In addition to assessing lymphocyte subpopulation differences between ALD patients and controls, we also compared subsets of alcoholic patients without cirrhosis or abstinent cirrhotic patients to normal controls.

RESULTS

The patient cohort primarily consisted of older men. Active alcoholism was present in 66.1%. Reported average daily alcohol intake was 164.9 g and the average lifetime cumulative intake was 2211.6 kg. Cirrhosis was present in 39.3% of the patients and 66.1% had significant fibrosis (perisinusoidal and portal/periportal fibrosis, bridging fibrosis, or cirrhosis) in their liver samples. The average Mayo end-stage liver disease score was 7.6. No hereditary hemochromatosis genotypes were found. ALD patients (n = 56) presented with significant lymphopenia (1.5 × 10(9)/L ± 0.5 × 10(9)/L vs 2.1 × 10(9)/L ± 0.5 × 10(9)/L, P < 0.0001), due to a decrease in all lymphocyte subpopulations, except for NK lymphocytes: CD3(+) (1013.0 ± 406.2/mm(3) vs 1523.0 ± 364.6/mm(3), P < 0.0001), CD4(+) (713.5 ± 284.7/mm(3) vs 992.4 ± 274.7/mm(3), P < 0.0001), CD8(+) (262.3 ± 140.4/mm(3) vs 478.9 ± 164.6/mm(3), P < 0.0001), and CD19(+) (120.6 ± 76.1/mm(3) vs 264.6 ± 88.0/mm(3), P < 0.0001). CD8(+) lymphocytes suffered the greatest reduction, as evidenced by an increase in the CD4(+)/CD8(+) ratio (3.1 ± 1.3 vs 2.3 ± 0.9, P = 0.013). This ratio was associated with the stage of fibrosis on liver biopsy (r s = 0.342, P = 0.01) and with Child-Pugh score (r s = 0.482, P = 0.02). The number of CD8(+) lymphocytes also had a positive association with serum ferritin levels (r s = 0.345, P = 0.009). Considering only patients with active alcoholism but not cirrhosis (n = 27), we found similar reductions in total lymphocyte counts (1.8 × 10(9)/L ± 0.3 × 10(9)/L vs 2.1 × 10(9)/L ± 0.5 × 10(9)/L, P = 0.018), and in populations of CD3(+) (1164.7 ± 376.6/mm(3) vs 1523.0 ± 364.6/mm(3), P = 0.001), CD4(+) (759.8 ± 265.0/mm(3) vs 992.4 ± 274.7/mm(3), P = 0.003), CD8(+) (330.9 ± 156.3/mm(3) vs 478.9 ± 164.6/mm(3), P = 0.002), and CD19(+) (108.8 ± 64.2/mm(3) vs 264.6 ± 88.0/mm(3), P < 0.0001). In these patients, the CD4(+)/CD8(+) ratio and the number of NK lymphocytes was not significantly different, compared to controls. Comparing patients with liver cirrhosis but without active alcohol consumption (n = 11), we also found significant lymphopenia (1.3 × 10(9)/L ± 0.6 × 10(9)/L vs 2.1 × 10(9)/L ± 0.5 × 10(9)/L, P < 0.0001) and decreases in populations of CD3(+) (945.5 ± 547.4/mm(3) vs 1523.0 ± 364.6/mm(3), P = 0.003), CD4(+) (745.2 ± 389.0/mm(3) vs 992.4 ± 274.7/mm(3), P = 0.032), CD8(+) (233.9 ± 120.0/mm(3) vs 478.9 ± 164.6/mm(3), P < 0.0001), and CD19(+) (150.8 ± 76.1/mm(3) vs 264.6 ± 88.0/mm(3), P = 0.001). The NK lymphocyte count was not significantly different, but, in this group, there was a significant increase in the CD4(+)/CD8(+) ratio (3.5 ± 1.3 vs 2.3 ± 0.9, P = 0.01).

CONCLUSION

All patient subsets presented with decreased lymphocyte counts, but only patients with advanced fibrosis presented with a significant increase in the CD4(+)/CD8(+) ratio.

Impact of MHC class II polymorphism on blood counts of CD4+ T lymphocytes in macaque

While the number of peripheral blood T lymphocytes and of their two main subsets (CD4+CD8- and CD4-CD8+) varies little in a given healthy individual, substantial variation is observed between individuals. It was proposed that these counts could be influenced by MHC polymorphisms because of the well-established role of MHC molecules in thymic T lymphocyte maturation and presentation of antigenic peptides to peripheral T lymphocytes. To test this hypothesis, we have chosen the crab-eating macaque (Macaca fascicularis), an animal model phylogenetically close to man. We selected the Philippine macaque population because of a restriction of the MHC polymorphism in this islander population. Peripheral blood lymphocytes were counted with an automated analyzer and T lymphocyte subsets were assessed by immunolabeling and flow cytometry. The MHC polymorphism was investigated in 200 unrelated subjects using 14 microsatellites markers distributed across the MHC and the DRB locus that was genotyped by denaturing gradient gel electrophoresis and sequencing. All markers were in Hardy-Weinberg equilibrium. Allelic associations were tested with the UNPHASED software. We revealed a significant influence of the MHC class II region on CD4+ T lymphocyte blood count with the largest effect associated with a two-locus haplotypes combining the DRACA allele 274 and the DRB haplotype #8a (p < 8 × 10(-7)). Our data should stimulate a similar association study of the CD4+ T cell counts in humans.

Low numbers of CD8+ T lymphocytes in hereditary haemochromatosis are explained by a decrease of the most mature CD8+ effector memory T cells

Low CD8(+) T lymphocyte numbers have long been described in hereditary haemochromatosis (HH). Recently, two conserved haplotypes localized near the microsatellite D6S105 at the major histocompatibility complex (MHC) class I region were described predicting the clinical expression of HH and the CD8(+) T lymphocyte numbers. The A-A-T haplotype was associated with a severe clinical expression of HH and low CD8(+) T lymphocyte numbers, while the G-G-G haplotype was associated with a milder clinical expression of HH and high CD8(+) T lymphocyte numbers. As CD8(+) T lymphocytes are a very heterogeneous population, in this study we analysed the CD8(+) subpopulations of naive, central memory (T(CM)) and effector memory (T(EM)), and further subsets of CD8(+) T(EM) cells in 47 HH patients and 68 controls. In addition, association studies were conducted between the conserved haplotypes and the CD8(+) T cell subpopulations in HH. Variations of the numbers of naive and central memory cells with age were similar between HH patients and controls. For T(EM) cells and the T(EM) CD27(-)CD28(-) subset no effect of age was observed in HH [R(2) = 0.001, not significant (n.s.) and R(2) = 0.01, n.s., respectively] contrasting with the increasing of these subpopulations with age in controls (R(2) = 0.09, P = 0.017 and R(2) = 0.22, P = 0.0005, respectively). Interestingly, patients homozygous for the A-A-T haplotype have lower numbers of CD8(+) T(EM) cells due especially to lower numbers of T(EM) CD27(-)CD28(-) (0.206 +/- 0.119 and 0.066 +/- 0.067 x 10(6) cells/ml, respectively) than patients carrying the G-G-G haplotype (0.358 +/- 0.195 and 0.246 +/- 0.202 x 10(6) cells/ml, respectively). This may suggest an inability of HH patients to differentiate the CD8(+) T cells into the most mature phenotype.

Human Leukocyte Antigens I and II Haplotypes Associated With Human Papillomavirus 16-Positive Invasive Cervical Cancer in Mexican Women

Infection with human papillomavirus (HPV), mainly HPV type 16, is the major etiologic factor associated with cervical cancer (CC), but HPV infection alone is not sufficient for progression of precursor lesions. Host genetic susceptibility may lead to abnormal immune response resulting from virus persistence. Several studies have suggested a possible association with specific human leukocyte antigen (HLA) class I and II alleles and CC, but results are not consistent. The association of genetic HLA class I (A and B) and HLA class II (DR*B1 and DQ*B1) haplotypes with HPV16-positive CC (n = 104) and base population controls (n = 104) was evaluated in this Mexican population study. Sequence-specific primer HLA genes were determined by polymerase chain reaction (PCR)-based methods in peripheral blood cell counts (PCR sequence-specific oligonucleotides). The cervical swabs of 208 women were tested for HPV16 by Hybrid Capture II. Allele and haplotype HLA frequencies, Hardy-Weinberg tests, and a haplotype homogeneity test were estimated using the Arlequin software v. 3.01. Odds ratio (OR) was calculated to compare cases and control women. Consistent associations across other studies in women with CC and infected by HPV16 were observed for HLA-DRB1*15 (OR, 3.9; 95% CI, 1.6-10.2) and the haplotype DRB1*15 DQB1*0602 (OR, 4.1; 95% CI, 1.4-12.7) compared with control women. The HLA-A2-B44-DR4-DQ*0302, HLA-A24-B35-DR16-DQ*0301, and HLA-A2-B40-DR4-DQ*0302 haplotypes showed a positive association with CC (OR, >1), whereas HLA-A2-B39-DR4-DQ*0302, HLA-A24-B35-DR4-DQ*0302, and HLA-A68-B40-DR4-DQ*0302 showed a negative association (OR, <1). These results support the hypothesis that some HLA class I and II haplotypes could be involved with susceptibility for developing CC.

Abbreviations:

Cervical Cancer-CC, confidence interval-CI, human leukocyte antigens-HLA, human papillomavirus-HPV, odds ratio-OR, polymerase chain reaction-PCR, relative risk-RR, relative light units-RLU, ribonucleic acid-RNA, sequence-sensitive oligonucleotide-SSO

A new 500 kb haplotype associated with high CD8+ T-lymphocyte numbers predicts a less severe expression of hereditary hemochromatosis

Background

Hereditary Hemochromatosis(HH) is a common genetic disorder of iron overload where the large majority of patients are homozygous for one ancestral mutation in the HFE gene. In spite of this remarkable genetic homogeneity, the condition is clinically heterogeneous, varying from a severe disease to an asymptomatic phenotype with only abnormal biochemical parameters. The recent recognition of the variable penetrance of the HH mutation in different large population studies demands the need to search for new modifiers of its phenotypic expression. The present study follows previous observations that MHC class-I linked genetic markers, associated with the setting of CD8+ T-lymphocyte numbers, could be clinically relevant modifiers of the phenotypic expression in HH, and aimed to find new markers that could be used as more reliable prognostic variables.

Methods

Haplotype analysis, including seven genetic markers within a 1 Mb region around the microsatellite D6S105 was performed in a group of 56 previously characterized C282Y homozygous Portuguese patients. Parameters analyzed in this study were total body iron stores, clinical manifestations related with HH and immunological parameters (total lymphocyte numbers, CD4+ and CD8+ T-lymphocyte numbers). An independent group of 10 C282Y homozygous patients from Vancouver, Canada, were also included in this study and analyzed for the same parameters.

Results

A highly conserved ancestral haplotype defined by the SNP markers PGBD1-A, ZNF193-A, ZNF165-T (designated as A-A-T) was found associated with both abnormally low CD8+ T-lymphocyte numbers and the development of a severe clinical expression of HH. In a small proportion of patients, another conserved haplotype defined by the SNP markers PGBD1-G, ZNF193-G, ZNF165-G (designated as G-G-G) was found associated with high CD8+ T-lymphocyte numbers and a milder clinical expression. Remarkably, the two conserved haplotypes defined in Portuguese patients were also observed in the geographically different population of Canadian patients, also predicting CD8+ T-lymphocyte numbers and the severity of disease.

Conclusion

These results may have important implications not only for approaching the question of the penetrance of the hemochromatosis gene in different world populations but also to further narrow the region of interest to find a candidate gene involved in the setting of CD8+ T-lymphocyte numbers in humans.

A putative gene located at the MHC class I region around the D6S105 marker contributes to the setting of CD8+ T-lymphocyte numbers in humans

Significant associations between human leucocyte antigen (HLA)-A and -B alleles and CD8+ T-lymphocyte numbers have been reported in the literature in both healthy populations and in HFE-haemochromatosis patients. In order to address whether HLA alleles themselves or alleles at linked genes are responsible for these associations, several genetic markers at the MHC class I region were typed on a population of 147 apparently healthy unrelated subjects phenotypically characterized for their CD8+ and CD4+ T-lymphocyte numbers. By using a machine learning approach, a set of rules was generated that predict the number of CD8+ T-lymphocyte numbers on the basis of the information of the D6S105 microsatellite alleles only. We demonstrate that the previously reported associations with HLA-A and -B alleles are due to the presence of common long (up to 4 megabases long) haplotypes that increased in frequency recently due to positive selection and that encompass a region where a putative gene contributing to the setting of CD8+ T lymphocytes is located, in the neighbourhood of microsatellite locus D6S105, in the 6p21.3 region.

Iron overload and immunity

Progress in the characterization of genes involved in the control of iron homeostasis in humans and in mice has improved the definition of iron overload and of the cells affected by it. The cell involved in iron overload with the greatest effect on immunity is the macrophage. Intriguing evidence has emerged, however, in the last 12 years indicating that parenchymal iron overload is linked to genes classically associated with the immune system. This review offers an update of the genes and proteins relevant to iron metabolism expressed in cells of the innate immune system, and addresses the question of how this system is affected in clinical situations of iron overload. The relationship between iron and the major cells of adaptive immunity, the T lymphocytes, will also be reviewed. Most studies addressing this last question in humans were performed in the clinical model of Hereditary Hemochromatosis. Data will also be reviewed demonstrating how the disruption of molecules essentially involved in adaptive immune responses result in the spontaneous development of iron overload and how they act as modifiers of iron overload.

The CD8+ T-lymphocyte profile as a modifier of iron overload in HFE hemochromatosis: an update of clinical and immunological data from 70 C282Y homozygous subjects

Hereditary hemochromatosis (HH) is a clinically heterogeneous disease. Among other factors, the individual immunological profile of CD8+ T-lymphocytes has been described to influence the severity of iron overload, with low numbers being negatively correlated with the total amount of body iron stored. With the objective of testing the modifier effect of the individual CD8+ T-lymphocyte profile on the levels of iron stores with age in HH, we reviewed the clinical and immunological data from a group of well-characterized C282Y homozygous HH subjects, regularly followed-up for a period of 20 years. A total of 70 subjects were analyzed. Sixty-four were adults (> or = 18 years): 42 males (mean age 47 +/- 14; range 22-75 years) and 22 females (mean age 46 +/- 14; range 19-65 years). Six were younger than 18 years, 5 males (mean age 9 +/- 4; range 5-14 years) and 1 female (15 years). The characterization of subjects included measurements, at diagnosis, of the iron parameters, transferrin saturation (TfSat) and serum ferritin, quantification of total body iron stores (TBIS) removed by phlebotomies, presence of associated clinical manifestations, and the T-cell immunophenotype (CD4+ and CD8+ T-lymphocytes) determined by flow cytometry. In general, statistically significant lower values of TfSat (67 +/- 17% vs. 89 +/- 14%, P = 0.0006) and ferritin levels (58 +/- 9 vs. 949 +/- 233 ng/ml, P = 0.02) were found in the young subjects in comparison to adults. After the age of 18, however, no further effect of age was significantly found on the biochemical iron parameters either in males or females. A modifier effect of the individual CD8+ T-lymphocyte profile on the association between iron stores and age was demonstrated by multiple regression analysis, where a significant correlation between TBIS and age was found only in males with low (< or = 0.41 x 10(6)/ml) CD8+ T-cell numbers (R2 = 0.43, P < 0.0001). In conclusion, in the present population of C282Y homozygous subjects, the CD8+ T-lymphocyte profile could be considered a modifier of the iron overload with increasing age in males, with low numbers predicting a severe outcome.

Haemochromatosis gene (HFE) mutations in viral-associated neoplasia: Linkage to cervical cancer

The present study examines the frequency of the two main HFE mutations (C282Y and H63D) in a randomly selected population of 346 individuals including 201 DNA samples from women with cervical neoplasia (including high-grade squamous intraepithelial lesions and invasive squamous cell carcinoma) and a control population of 146 women from the same geographical area. We found a significantly lower risk of development of cervical neoplasia in H63D carriers (OR = 0.56; 95% CI 0.35-0.92; p = 0.01). Multivariate logistic regression analysis confirms this observation (OR = 0.55; 95% CI 0.35-0.88, p = 0.01). Regarding the C282Y mutation no association was found (OR = 1.32; 95% CI 0.53-3.33; p = 0.52). In addition, a significant difference between H63D carrier and non-carrier women on the time-to-onset of cervical lesions was observed (log-rank test: p = 0.0012). These results indicate that HFE could be considered a candidate modifier gene of viral-related neoplasia such as cervical carcinoma possibly by a dual role on iron metabolism and immunological system.

A study of 82 extended HLA haplotypes in HFE-C282Y homozygous hemochromatosis subjects: relationship to the genetic control of CD8+ T-lymphocyte numbers and severity of iron overload

Background

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.

Methods

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.

Results

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 × 10⁶/ml), in comparison with subjects carrying only one copy of those alleles (0.46 ± 0.19 × 10⁶/ml) and subjects without any copy of those alleles (0.79 ± 0.15 × 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 × 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).

Conclusion

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.

HFE H63D mutation frequency shows an increase in Turkish women with breast cancer

BACKGROUND

The hereditary hemochromatosis gene HFE plays a pivotal role in iron homeostasis. The association between cancer and HFE hetero- or homozygosity has previously been shown including hepatocellular and nonhepatocellular malignancies. This study was performed to compare frequencies of HFE C282Y and H63D variants in Turkish women with breast cancer and healthy controls.

METHODS

Archived DNA samples of Hacettepe University Oncology Institute were used in this study. The HFE gene was investigated by PCR-RFLP.

RESULTS

All subjects studied were free from C282Y mutation. Thirty-nine patients had H63D mutation and were all heterozygous. H63D allele frequency was 22.2% (39/176) in the breast cancer patients, and 14% (28/200) in the healthy volunteers. Statistical analysis of cases with HFE H63D phenotype showed significant difference between breast cancer and healthy volunteers (P = 0.02).

CONCLUSION

Our results suggest that HFE H63D mutation frequencies were increased in the breast cancer patients in comparison to those in the general population. Also, odds ratios (odds ratio = 2.05) computed in this study suggest that H63D has a positive association with breast cancer.

Low serum transferrin levels in HFE C282Y homozygous subjects are associated with low CD8+ T lymphocyte numbers

Hereditary hemochromatosis (HH) is a genetic iron overload disease, in the majority of cases associated with homozygosity for the C282Y mutation of the HFE gene. In spite of this genetic homogeneity, there is a great clinical heterogeneity among HH patients. Low CD8(+) lymphocyte numbers have been associated with a more severe expression of iron overload in HH patients, and in experimental models of iron overload. HH patients present low serum transferrin levels. Transferrin is an indispensable resource for lymphopoiesis. Lymphocyte homeostasis follows general ecology rules of population dynamics that involve competition for limiting resources. In the present study, we questioned whether transferrin levels could be associated with the anomalies seen previously in lymphocyte subset numbers in HH patients. Transferrin levels, total and subset T lymphocyte counts were done in 426 apparently healthy subjects genotyped for HFE. All HFE C282Y carriers presented significantly lower serum transferrin levels than the wild type group, a difference that could not be explained solely by the degree of iron overload. Significant differences were also seen in transferrin levels between males and females, with females presenting higher average serum Transferrin levels. In the population of subjects with Transferrin levels lower than 248 mg/dl, a positive correlation was seen between the peripheral CD8(+) lymphocyte numbers and serum transferrin levels (R(2) = 2.41; r = 0.16; P = 0.018). To test the possible limiting resource effect of transferrin, the correlation between transferrin levels and CD8(+) lymphocyte numbers was scrutinized in 34 HH patients, homozygous for the C282Y mutation. In the homozygous males, where the lowest average transferrin levels were seen, another highly significant correlation was observed between Transferrin levels and CD8(+) numbers. This correlation points to a possible role of transferrin as a limiting resource for MHC class I dependent lymphocyte proliferation, an effect that was not observed in C282Y homozygous female patients.

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Total blood lymphocyte counts in hemochromatosis probands with HFE C282Y homozygosity: relationship to severity of iron overload and HLA-A and -B alleles and haplotypes

Background

It has been reported that some persons with hemochromatosis have low total blood lymphocyte counts, but the reason for this is unknown.

Methods

We measured total blood lymphocyte counts using an automated blood cell counter in 146 hemochromatosis probands (88 men, 58 women) with HFE C282Y homozygosity who were diagnosed in medical care. Univariate and multivariate analyses of total blood lymphocyte counts were evaluated using these variables: sex; age, transferrin saturation, and serum ferritin concentration at diagnosis; units of blood removed by phlebotomy to achieve iron depletion; and human leukocyte antigen (HLA)-A and -B alleles and haplotypes.

Results

The mean age at diagnosis was 49 ± 14 years (range 18 – 80 years) in men and 50 ± 13 years (range 22 – 88 years) in women. The correlations of total blood lymphocyte counts with sex, age, transferrin saturation, and serum ferritin concentration at diagnosis, and units of blood removed by phlebotomy to achieve iron depletion were not significant at the 0.05 level. Univariate analyses revealed significant associations between total blood lymphocyte counts and presence of the HLA-A*01, -B*08, and -B*14 alleles, and the A*01-B*08 haplotype. Presence of the A*01 allele, B*08 allele, or A*01-B*08 haplotype were associated with a lower total blood lymphocyte count, whereas presence of the B*14 allele was associated with a greater total blood lymphocyte count. There was an inverse association of total blood lymphocyte count with units of phlebotomy to achieve iron depletion, serum ferritin concentration, and with presence of the A*01-B*08 haplotype.

Conclusion

We conclude that there is a significant inverse relationship of total blood lymphocyte counts and severity of iron overload in hemochromatosis probands with HFE C282Y homozygosity. The presence of the HLA-A*01 allele or the -B*08 allele was also associated with significantly lower total blood lymphocyte counts, whereas presence of the -B*14 allele was associated with significantly higher total blood lymphocyte counts. In univariate and multivariate analyses, total blood lymphocyte counts were significantly lower in probands with the HLA-A*01-B*08 haplotype than in probands without this haplotype.