Anomalies of the CD8+ T cell pool in haemochromatosis: HLA-A3-linked expansions of CD8+CD28- T cells

The role of iron homeostasis in remodeling immune function and regulating inflammatory disease

The essential trace element iron regulates a wide range of biological processes in virtually all living organisms. Because both iron deficiency and iron overload can lead to various pathological conditions, iron homeostasis is tightly regulated, and understanding this complex process will help pave the way to developing new therapeutic strategies for inflammatory disease. In recent years, significant progress has been made with respect to elucidating the roles of iron and iron-related genes in the development and maintenance of the immune system. Here, we review the timing and mechanisms by which systemic and cellular iron metabolism are regulated during the inflammatory response and during infectious disease, processes in which both the host and the pathogen compete for iron. We also discuss the evidence and implications that immune cells such as macrophages, T cells, and B cells require sufficient amounts of iron for their proliferation and for mediating their effector functions, in which iron serves as a co-factor in toll-like receptor 4 (TLR4) signaling, mitochondrial respiration, posttranslational regulation, and epigenetic modification. In addition, we discuss the therapeutic implications of targeting ferroptosis, iron homeostasis and/or iron metabolism with respect to conferring protection against pathogen infection, controlling inflammation, and improving the efficacy of immunotherapy.

Iron in infection and immunity

Iron is an essential micronutrient for virtually all living cells. In infectious diseases, both invading pathogens and mammalian cells including those of the immune system require iron to sustain their function, metabolism and proliferation. On the one hand, microbial iron uptake is linked to the virulence of most human pathogens. On the other hand, the sequestration of iron from bacteria and other microorganisms is an efficient strategy of host defense in line with the principles of 'nutritional immunity'. In an acute infection, host-driven iron withdrawal inhibits the growth of pathogens. Chronic immune activation due to persistent infection, autoimmune disease or malignancy however, sequesters iron not only from infectious agents, autoreactive lymphocytes and neoplastic cells but also from erythroid progenitors. This is one of the key mechanisms which collectively result in the anemia of chronic inflammation. In this review, we highlight the most important interconnections between iron metabolism and immunity, focusing on host defense against relevant infections and on the clinical consequences of anemia of inflammation.

Expression patterns of CD28 and CTLA-4 in early, chronic, and untreated rheumatoid arthritis

Background

T‐cell activation pathways have been proposed as trigger mechanisms in the pathogenesis of rheumatoid arthritis (RA). CD28 and CTLA‐4 play major roles in regulating the stimulatory and inhibitory co‐signals in T cells.

Objective

To analyze the association between soluble and surface expression of CD28 and CTLA‐4 with the clinical parameters of RA patients.

Methods

A total of 35 RA patients classified as early RA (n = 14), chronic RA (n = 14), and untreated RA (n = 7), as well as 7 age‐ and sex‐matched control subjects (CS) were included. Surface expression of CD28 and CTLA‐4 on T cells was evaluated by flow cytometry. Soluble levels of CD28 (sCD28), CTLA‐4 (sCTLA‐4), and anti‐CCP antibodies were measured by ELISA.

Results

A significant lower percentage of CD8 + T cells positive to CD28 (CS = 64.9% vs RA = 42.7%, P = .04), and diminished surface expression of CD28 (CS: MFI = 122.9 vs RA: MFI = 33.1, P = .006), were found in chronic RA patients compared to CS. Higher sCD28 were observed in early RA patients compared with chronic RA patients (P < .05). sCTLA‐4 was found increased in untreated RA patients compared to early RA patients (P < .05). sCD28 concentration correlated with anti‐CCP levels (rho = −0.12; P = .032). The soluble and surface expressions of CTLA‐4 were not associated with RA clinical parameters.

Conclusions

In RA, the percentage of CD8 + CD28+ T cells decreases and expresses fewer membrane CD28 than CS. sCD28 levels are lower in chronic RA and are associated negatively with anti‐CCP levels. sCTLA 4 levels are lower in early RA patients than in untreated RA patients.

HFE Related Hemochromatosis: Uncovering the Inextricable Link between Iron Homeostasis and the Immunological System

The HFE gene (OMIM 235200), most commonly associated with the genetic iron overload disorder Hemochromatosis, was identified by Feder et al. in 1996, as a major histocompatibilty complex (MHC) class I like gene, first designated human leukocyte antigen-H (HLA-H). This discovery was thus accomplished 20 years after the realization of the first link between the then "idiopathic" hemochromatosis and the human leukocyte antigens (HLA). The availability of a good genetic marker in subjects homozygous for the C282Y variant in HFE (hereditary Fe), the reliability in serum markers such as transferrin saturation and serum ferritin, plus the establishment of noninvasive methods for the estimation of hepatic iron overload, all transformed hemochromatosis into a unique age related disease where prevention became the major goal. We were challenged by the finding of iron overload in a 9-year-old boy homozygous for the C282Y HFE variant, with two brothers aged 11 and 5 also homozygous for the mutation. We report a 20 year follow-up during which the three boys were seen yearly with serial determinations of iron parameters and lymphocyte counts. This paper is divided in three sections: Learning, applying, and questioning. The result is the illustration of hemochromatosis as an age related disease in the transition from childhood to adult life and the confirmation of the inextricable link between iron overload and the cells of the immune system.

Iron in the Tumor Microenvironment-Connecting the Dots

Iron metabolism and tumor biology are intimately linked. Iron facilitates the production of oxygen radicals, which may either result in iron-induced cell death, ferroptosis, or contribute to mutagenicity and malignant transformation. Once transformed, malignant cells require high amounts of iron for proliferation. In addition, iron has multiple regulatory effects on the immune system, thus affecting tumor surveillance by immune cells. For these reasons, inconsiderate iron supplementation in cancer patients has the potential of worsening disease course and outcome. On the other hand, chronic immune activation in the setting of malignancy alters systemic iron homeostasis and directs iron fluxes into myeloid cells. While this response aims at withdrawing iron from tumor cells, it may impair the effector functions of tumor-associated macrophages and will result in iron-restricted erythropoiesis and the development of anemia, subsequently. This review summarizes our current knowledge of the interconnections of iron homeostasis with cancer biology, discusses current clinical controversies in the treatment of anemia of cancer and focuses on the potential roles of iron in the solid tumor microenvironment, also speculating on yet unknown molecular mechanisms.

Human Leukocyte Antigen (HLA) and Immune Regulation: How Do Classical and Non-Classical HLA Alleles Modulate Immune Response to Human Immunodeficiency Virus and Hepatitis C Virus Infections?

The genetic factors associated with susceptibility or resistance to viral infections are likely to involve a sophisticated array of immune response. These genetic elements may modulate other biological factors that account for significant influence on the gene expression and/or protein function in the host. Among them, the role of the major histocompatibility complex in viral pathogenesis in particular human immunodeficiency virus (HIV) and hepatitis C virus (HCV), is very well documented. We, recently, added a novel insight into the field by identifying the molecular mechanism associated with the protective role of human leukocyte antigen (HLA)-B27/B57 CD8⁺ T cells in the context of HIV-1 infection and why these alleles act as a double-edged sword protecting against viral infections but predisposing the host to autoimmune diseases. The focus of this review will be reexamining the role of classical and non-classical HLA alleles, including class Ia (HLA-A, -B, -C), class Ib (HLA-E, -F, -G, -H), and class II (HLA-DR, -DQ, -DM, and -DP) in immune regulation and viral pathogenesis (e.g., HIV and HCV). To our knowledge, this is the very first review of its kind to comprehensively analyze the role of these molecules in immune regulation associated with chronic viral infections.

The hemochromatosis protein HFE 20 years later: An emerging role in antigen presentation and in the immune system

Introduction

Since its discovery, the hemochromatosis protein HFE has been primarily defined by its role in iron metabolism and homeostasis, and its involvement in the genetic disease termed hereditary hemochromatosis (HH). While HH patients are typically afflicted by dysregulated iron levels, many are also affected by several immune defects and increased incidence of autoimmune diseases that have thereby implicated HFE in the immune response. Growing evidence has supported an immunological role for HFE with recent studies describing HFE specifically as it relates to MHC I antigen presentation.

Methods/Results

Here, we present a comprehensive overview of the relationship between iron metabolism, HFE, and the immune system to better understand the origin and cause of immune defects in HH patients. We further describe the role of HFE in MHC I antigen presentation and its potential to impair autoimmune responses in homeostatic conditions, a mechanism which may be exploited by tumors to evade immune surveillance.

Conclusion

Overall, this increased understanding of the role of HFE in the immune response sets the stage for better treatment and management of HH and other iron‐related diseases, as well as of the immune defects related to this condition.

Divide, Conquer, and Sense: CD8+CD28- T Cells in Perspective

Understanding the rationale for the generation of a pool of highly differentiated effector memory CD8⁺ T cells displaying a weakened capacity to scrutinize for peptides complexed with major histocompatibility class I molecules via their T cell receptor, lacking the “signal 2” CD28 receptor, and yet expressing a highly diverse array of innate receptors, from natural killer receptors, interleukin receptors, and damage-associated molecular pattern receptors, among others, is one of the most challenging issues in contemporary human immunology. The prevalence of these differentiated CD8⁺ T cells, also known as CD8⁺CD28⁻, CD8⁺KIR⁺, NK-like CD8⁺ T cells, or innate CD8⁺ T cells, in non-lymphoid organs and tissues, in peripheral blood of healthy elderly, namely centenarians, but also in stressful and chronic inflammatory conditions suggests that they are not merely end-of-the-line dysfunctional cells. These experienced CD8⁺ T cells are highly diverse and capable of sensing a variety of TCR-independent signals, which enables them to respond and fine-tune tissue homeostasis.

Herpes simplex virus type 1 (HSV-1) specific T-cell generation from HLA-A1- and HLA-A2-positive donors for adoptive immunotherapy

BACKGROUND AIMS

Herpes simplex virus (HSV) reactivation and infection is common in patients undergoing hematopoietic stem cell transplant (HSCT) and requires routine antiviral prophylaxis. Drug-resistant strains are increasingly common, and effective alternative therapy is currently unavailable. We generated and characterized HSV-1-specific T cells for use in adoptive cellular immunotherapy following allogeneic stem cell transplantation.

METHODS

Peripheral blood mononuclear cells from HLA-A1 and HLA-A2 HSV-seropositive hereditary hemochromatosis donors were used as the antigen source. Three HLA-A1 and four HLA-A2 specific epitopes were used for stimulation of T cells. Cells were stimulated with antigen-pulsed dendritic cells and cultured for 21 days in medium with interleukin (IL)-2. Cultured cells were phenotyped and tested for cytokine production, proliferation and cytotoxicity.

RESULTS

There was a 5.3-fold expansion in total cell numbers over 21 days of culture, with 35% of T cells being CD8 positive. Thirty-five percent, 21% and 5% of CD8 cells secreted interferon-γ, tumor necrosis factor-α and IL-2 upon HSV antigen re-stimulation. More than 50% of antigen-specific T cells secreted multiple cytokines. Cultured T cells proliferated upon antigen re-stimulation and lysed HSV-1 peptide and virus-infected targets.

CONCLUSIONS

It is feasible to generate functional HSV-1 specific T cells from the blood of HLA-A1 and HLA-A2 HSV-seropositive donors using specific peptides. The utility of these cells in preventing and treating HSV-1 reactivation in allogeneic HSCT will need to be tested clinically.

Haplotype Analysis of Hemochromatosis Gene Polymorphisms in Chronic Hepatitis C Virus Infection: A Case Control Study

Background

Chronic hepatitis C virus (HCV) infection is frequently associated with elevated serum iron markers. Polymorphisms in the hemochromatosis (HFE) genes are responsible for iron accumulation in most cases of hemochromatosis, and may play a role in HCV infection.

Objectives

We aimed to assess the prevalence of HFE gene polymorphisms in a group of Iranian HCV-infected patients, and to explore the association of these polymorphisms with HCV infection.

Patients and Methods

HFE gene polymorphisms were examined in a total of 69 HCV patients and 69 healthy controls using polymerase chain reaction and restriction fragment length polymorphism techniques. Haplotype and diplotype analyses were performed using PHASE software.

Results

In a recessive analysis model of the His63Asp (H63D) locus (HH vs. HD + DD), the HH genotype was more common in patients compared to controls (adjusted P = 0.012; OR = 6.42 [95% CI: 1.51 - 27.33]). Also, in a recessive analysis model of the Cys282Tyr (C282Y) locus (CC vs. CY + YY), the CC genotype was more frequent in patients compared to controls (adjusted P = 0.03; OR = 5.06 [95% CI: 1.13 - 22.06]). In addition, there was a significant association between the HC haplotype and the HCDC diplotype and HCV infection.

Conclusions

Polymorphism in the hemochromatosis gene may confer some degree of risk for HCV infection, and individuals carrying the H and C alleles may be susceptible to this disease; however, a larger sample of HCV patients and healthy individuals may be necessary to further illustrate the role of these polymorphisms in HCV.

Lymphocyte gene expression signatures from patients and mouse models of hereditary hemochromatosis reveal a function of HFE as a negative regulator of CD8+ T-lymphocyte activation and differentiation in vivo

Abnormally low CD8⁺ T-lymphocyte numbers is characteristic of some patients with hereditary hemochromatosis (HH), a MHC-linked disorder of iron overload. Both environmental and genetic components are known to influence CD8⁺ T-lymphocyte homeostasis but the role of the HH associated protein HFE is still insufficiently understood. Genome-wide expression profiling was performed in peripheral blood CD8⁺ T lymphocytes from HH patients selected according to CD8⁺ T-lymphocyte numbers and from Hfe^-/- mice maintained either under normal or high iron diet conditions. In addition, T-lymphocyte apoptosis and cell cycle progression were analyzed by flow cytometry in HH patients. HH patients with low CD8⁺ T-lymphocyte numbers show a differential expression of genes related to lymphocyte differentiation and maturation namely CCR7, LEF1, ACTN1, NAA50, P2RY8 and FOSL2, whose expression correlates with the relative proportions of naïve, central and effector memory subsets. In addition, expression levels of LEF1 and P2RY8 in memory cells as well as the proportions of CD8⁺ T cells in G2/M cell cycle phase are significantly different in HH patients compared to controls. Hfe^-/- mice do not show alterations in CD8⁺ T-lymphocyte numbers but differential gene response patterns. We found an increased expression of S100a8 and S100a9 that is most pronounced in high iron diet conditions. Similarly, CD8⁺ T lymphocytes from HH patients display higher S100a9 expression both at the mRNA and protein level. Altogether, our results support a role for HFE as a negative regulator of CD8⁺ T-lymphocyte activation. While the activation markers S100a8 and S100a9 are strongly increased in CD8⁺ T cells from both, Hfe^-/- mice and HH patients, a differential profile of genes related to differentiation/maturation of CD8⁺ T memory cells is evident in HH patients only. This supports the notion that HFE contributes, at least in part, to the generation of low peripheral blood CD8⁺ T lymphocytes in HH.

T lymphocyte-derived TNF and IFN-γ repress HFE expression in cancer cells

The immune system and tumors are closely intertwined initially upon tumor development. During this period, tumors evolve to promote self-survival through immune escape, including by targeting crucial components involved in the presentation of antigens to the immune system in order to avoid recognition. Accordingly, components involved in MHC I presentation of tumor antigens are often mutated and down-regulated targets in tumors. On the other hand, the immune system has been shown to influence tumors through production of immunosuppressive cytokines, recruitment and polarization of cells favoring or impeding tumor escape or through production of anti-tumor cytokines promoting tumor rejection. We previously discovered that the hemochromatosis protein HFE, a negative regulator of iron absorption, dampens classical MHC I antigen presentation. In this study, we evaluated the impact of activated T lymphocytes purified from peripheral blood mononuclear cells (PBMC) on HFE expression in tumor cell lines. We co-cultured tumor cell lines from melanoma, lung, and kidney cancers with anti-CD3-activated PBMC and established that HFE expression is increased in tumor cell lines compared to healthy tissues, whilst being down-regulated significantly upon exposure to activated PBMC. HFE down-regulation was mediated by both CD4 and CD8 T lymphocytes, through production of soluble mediators, namely TNF and IFN-γ. These results suggest that the immune system may modulate tumor HFE expression in inflammatory conditions in order to regulate MHC I antigen presentation and promote tumor clearance.

Physiological implications of NTBI uptake by T lymphocytes

In iron overload disorders a significant fraction of the total iron circulates in the plasma as low molecular weight complexes not bound to transferrin, known as non-transferrin-bound iron (NTBI). By catalyzing the formation of free radicals, NTBI accumulation results in oxidative stress and cellular damage, being a major cause of organ toxicity. NTBI is rapidly and preferentially cleared from circulation by the liver and the myocardium, the main disease targets in iron overload conditions. We have recently demonstrated that human peripheral blood T lymphocytes take up NTBI in vitro, with a pattern that resembles that of hepatocytes. Since T lymphocytes constitute a numerically important component of the circulating cell pool, these findings support a putative role for this cell type in the systemic protection against iron toxicity. Here we tested the hypothesis that the circulating peripheral blood T lymphocyte pool constitutes an important storage compartment for NTBI and is thus a modifier of NTBI deposition in target organs. First we show that NTBI uptake by human T lymphocytes increases the expression of the iron-storage protein ferritin and of the iron exporter ferroportin via an IRE-dependent mechanism. NTBI retention by T lymphocytes is shown to be critically controlled by the hepcidin-mediated modulation of ferroportin both in vitro and in vivo. Finally, the protective effect of T lymphocytes was tested by analyzing the patterns of iron accumulation in the T lymphocyte-deficient mouse model Foxn1^nu before and after reconstitution with T lymphocytes by adoptive transfer. The results confirmed a significant increase of liver and pancreas iron accumulation in T lymphocyte-deficient mice. NTBI accumulation in the liver and spleen was prevented by reconstitution with syngeneic T lymphocytes. Altogether, our results demonstrate that T lymphocytes are important components of a circulating “NTBI storage compartment” and show its physiological relevance as a modifier of tissue iron overload.

Conditional deletion of ferritin h in mice reduces B and T lymphocyte populations

The immune system and iron availability are intimately linked as appropriate iron supply is needed for cell proliferation, while excess iron, as observed in hemochromatosis, may reduce subsets of lymphocytes. We have tested the effects of a ferritin H gene deletion on lymphocytes. Mx-Cre mediated conditional deletion of ferritin H in bone marrow reduced the number of mature B cells and peripheral T cells in all lymphoid organs. FACS analysis showed an increase in the labile iron pool, enhanced reactive oxygen species formation and mitochondrial depolarization. The findings were confirmed by a B-cell specific deletion using Fth^lox/lox; CD19-Cre mice. Mature B cells were strongly under-represented in bone marrow and spleen of the deleted mice, whereas pre-B and immature B cells were not affected. Bone marrow B cells showed increased proliferation as judged by the number of cells in S and G2/M phase as well as BrdU incorporation. Upon in vitro culture with B-cell activating factor of the tumor necrosis factor family (BAFF), ferritin H-deleted spleen B cells showed lower survival rates than wild type cells. This was partially reversed with iron-chelator deferiprone. The loss of T cells was also confirmed by a T cell-specific deletion in Fth^lox/lox;CD4-Cre mice. Our data show that ferritin H is required for B and T cell survival by actively reducing the labile iron pool. They further suggest that natural B and T cell maturation is influenced by intracellular iron levels and possibly deregulated in iron excess or deprivation.

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.

ER Stress and Iron Homeostasis: A New Frontier for the UPR

The C282Y mutation of HFE accounts for the majority of cases of the iron overload disease Hereditary Hemochromatosis (HH). The conformational changes introduced by this mutation impair the HFE association with β₂-microglobulin (β₂m) and the cell surface expression of the protein: with two major consequences. From a functional perspective, the ability of HFE to bind to transferrin receptors 1 and 2 is lost in the C282Y mutant, thus affecting hepcidin regulation. Also due to the faulty assembly with β₂m, HFE-C282Y molecules remain in the endoplasmic reticulum (ER) as aggregates that undergo proteasomal degradation and activate an Unfolded Protein Response (UPR). UPR activation, regardless of the ER stress stimuli, was shown to reshape the expression profile of iron-related genes and to decrease MHC-I cell surface expression. The possibility of a HFE-C282Y-mediated interplay between the UPR and iron homeostasis influencing disease progression and the clinical heterogeneity among C282Y carriers is discussed. The responsiveness of the ER chaperone calreticulin to both ER and iron-induced oxidative stresses, and its correlation with HH patients' phenotype, reinforce the interest of dissecting the UPR signaling/iron metabolism crosstalk and points to the potential clinical value of use of pharmacological chaperones in HFE-HH.

Highly sensitivity adhesion molecules detection in hereditary haemochromatosis patients reveals altered expression

Several abnormalities in the immune status of patients with hereditary haemochromatosis (HH) have been reported, suggesting an imbalance in their immune function. This may include persistent production of, or exposure to, altered immune signalling contributing to the pathogenesis of this disorder. Adhesion molecules L-, E- and P-Selectin, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) are some of the major regulators of the immune processes and altered levels of these proteins have been found in pathological states including cardiovascular diseases, arthritis and liver cancer. The aim of this study was to assess L-, E- and P-Selectin, ICAM-1 and VCAM-1 expression in patients with HH and correlate these results with HFE mutation status and iron indexes. A total of 139 subjects were diagnosed with HH (C282Y homozygotes = 87, C282Y/H63D = 26 heterozygotes, H63D homozygotes = 26), 27 healthy control subjects with no HFE mutation (N/N), 18 normal subjects heterozygous for the H63D mutation served as age-sex-matched controls. We observed a significant decrease in L-selectin (P = 0.0002) and increased E-selectin and ICAM-1 (P = 0.0006 and P = 0.0059) expression in HH patients compared with healthy controls. This study observes for the first time that an altered adhesion molecules profile occurs in patients with HH that is associated with specific HFE genetic component for iron overload, suggesting that differential expression of adhesion molecules may play a role in the pathogenesis of HH.

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.

Premature senescence of T lymphocytes from patients with beta-thalassemia major

Several researches have demonstrated a suppressed cell mediated immunity in patients with beta-thalassemia major. To know whether the premature aging of T cells is involved in abnormalities of cell mediated immunity, the biomarkers of immunosenescence including telomerase activity, apoptosis, and the expression of CD28 and CD95 were evaluated in T lymphocytes from beta-thalassemia major patients. The ex vivo spontaneous apoptosis in CD4(+) or CD8(+) T cells from patients and healthy subjects was assessed by an in situ TdT mediated dUTP-biotin nick end labelling (TUNEL) assay after 24h incubation in medium. Flow cytometric data revealed that lymphocytes from beta-thalassemia patients were resistant to spontaneous apoptosis compared to the normal lymphocytes. Moreover, the percentages of TUNEL(+)CD4(+) or TUNEL(+)CD8(+) T cells from patients were significantly lower than those control cells. Quantitative determination of telomerase activity in resting and activated T cells was performed using the Telomeric Repeat Amplification Protocol (TRAP). The results showed a decreased telomerase activity of activated T cells in patients with thalassemia major compared to that in healthy controls. However, the percentages of CD8(+)CD28(-) and CD3(+)CD95(+) T lymphocytes were significantly higher in thalassemia patients, indicating the phenotypes associated with senescent T lymphocytes. These data provide evidences for the occurrence of accelerated aging of T cells in beta-thalassemia major; possibly result in abnormal T cell function leading to suppressed cell mediated immunity.

CD8+CD28-, suppressive T cells in systemic lupus erythematosus

Recent studies show that a CD8+CD28- phenotype of T-cell population inhibits the reactivity of T-helper cells either by a contact-dependent mechanism or with secreting suppressive cytokines. In this study, we have explored the peripheral blood CD8+CD28- T-cell population in 53 patients with systemic lupus erythematosus (SLE) in comparison to healthy and diseased control groups. The distribution of CD28- cells within CD8+ population has been found significantly lower in patients with SLE than in healthy individuals. While there were no significant differences in the expression of costimulatory molecules CD80 and CD86, the CD40 expression on monocytes was found significantly lower and there was a slight decrease of expression of Interleukin-10 (IL-10) in CD8+CD28- population in patients with SLE. The Transforming growth factor-beta (TGF-beta) mRNA expression was found higher in CD8+CD28- T cells. Neither activation induced nor time-dependent change in the frequency of CD8+CD28- cells has been observed following stimulation at various time-points indicating that the control of CD28 expression was not dependent on the presence of sustained stimulations. Decrease in CD8+CD28- T cells which normally produce TGF-beta and their low-level IL-10 content may reflect impaired T-cell suppression and accordingly, increased T cell help to autoreactive B cells in patients with SLE.

The unfolded protein response in hereditary haemochromatosis

To cope with the accumulation of unfolded or misfolded proteins the endoplasmic reticulum (ER) has evolved specific signalling pathways collectively called the unfolded protein response (UPR). Elucidation of the mechanisms governing ER stress signallinghas linked this response to the regulation of diverse physiologic processes as well as to the progression of a number of diseases. Interest in hereditary haemochromatosis (HH) has focused on the study of proteins implicated in iron homeostasis and on the identification of new alleles related with the disease. HFE has been amongst the preferred targets of interest, since the discovery that its C282Y mutation was associated with HH. However, the discrepancies between the disease penetrance and the frequency of this mutation have raised the possibility that its contribution to disease progression might go beyond the mere involvement in regulation of cellular iron uptake. Recent findings revealed that activation of the UPR is a feature of HH and that this stress response may be involved in the genesis of immunological anomalies associated with the disease. This review addresses the connection of the UPR with HH, including its role in MHC-I antigen presentation pathway and possible implications for new clinical approaches to HH.

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.

Serum measures of iron status and HFE gene mutations in patients with hepatitis B virus infection

AIM

We tested associations between HFE mutations and hepatitis B virus (HBV) infection. We also explored measures of total body iron status and their association with chronic HBV infection.

METHODS

Serum measures of iron status and HFE mutations (C282Y, H63D, and S65C) were assessed in 344 Iranian patients with chronic HBV infection (214 asymptomatic carriers, 130 patients with chronic progressive liver disease [CPLD]) and 302 controls.

RESULTS

Frequencies of HFE mutations did not differ between patients with chronic HBV infection and controls (C282Y: P=0.9, H63D: P= 0.8, S65C: P=0.9). By logistic regression, advanced hepatic fibrosis was associated with HFE H63D mutation (OR=13.1, P=0.006; 95% CI=2.0-84.1). Higher levels of serum ferritin and transferrin saturation were observed in patients with CPLD than in healthy controls (P=0.0001 and 0.01, respectively, adjusted for age and sex). None of the serum iron measures was related to liver fibrosis stage or necroinflammatory grade.

CONCLUSION

Serum iron measures are associated with chronic progressive hepatitis B. Carriage of HFE mutations is not associated with the presence of chronic HBV infection or values of serum iron measures in this population, although HFE H63D is associated with more advanced hepatic fibrosis.

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.

Survival after liver transplantation in patients with hepatic iron overload: the national hemochromatosis transplant registry

BACKGROUND & AIMS

Previous uncontrolled studies have suggested that patients with hepatic iron overload have a poor outcome after liver transplantation. We examined the effect of HFE mutations on posttransplantation survival in patients with hepatic iron overload.

METHODS

Two hundred sixty patients with end-stage liver disease and hepatic iron overload were enrolled from 12 liver transplantation centers. Hepatic iron concentration (HIC), hepatic iron index (HII), HFE mutation status, and survival after liver transplantation were recorded.

RESULTS

HFE-associated hemochromatosis (HH) defined as homozygosity for the C282Y (n = 14, 7.2%) mutation or compound heterozygosity for the C282Y/H63D (n = 11, 5.6%) mutation was identified in 12.8% of patients. Survival postliver transplantation was significantly lower among patients with HH (1-, 3-, and 5-year survival rates of 64%, 48%, 34%, respectively) compared with simple heterozygotes (C282Y/wt or H63D/wt) or wild-type patients. Patients with HH had a hazard ratio for death of 2.6 (P = .002) after adjustment for age, United Network for Organ Sharing status, year of transplantation, and either elevated HII or HIC. Non-HH patients with hepatic iron overload also had significantly decreased survival when compared with the overall population undergoing liver transplantation (OR = 1.4, 95% CI: 1.15-1.61, P < .001).

CONCLUSIONS

One- and 5-year survivals after liver transplantation are significantly lower among patients with HFE-associated HH. Our data also suggest that hepatic iron overload may be associated with decreased survival after liver transplantation, even in patients without HH. Early diagnosis of hepatic iron overload using HFE gene testing and iron depletion prior to liver transplantation may improve posttransplantation survival, particularly among patients with HH.

HFE cross-talks with the MHC class I antigen presentation pathway

HFE is a protein known to be involved in iron metabolism; yet, other than its homology with major histocompatibility complex (MHC) class I molecules, it has not been described as having an immunologic function. Here we report that peripheral blood mononuclear cells (PBMCs) from patients with hereditary hemochromatosis (HH) carrying the C282Y mutation in HFE have reduced cell-surface expression of MHC class I due to an enhanced endocytosis rate of MHC class I molecules caused by premature peptide and β2-microglobulin dissociation. This faster turnover also leads to increased expression levels of cell-surface free class I heavy chains in mutant PBMCs. Biochemical analysis indicates an earlier peptide loading and endoplasmic reticulum maturation of MHC class I molecules in C282Y mutant cells. Thermostability assays further showed that in HFE mutants the MHC class I peptide loading gives rise to low-stability heterotrimers that dissociate prematurely during its intracellular traffic. The present results suggest the existence of an intriguing cross-talk between a particular HFE mutation and the classical MHC class I route. These findings constitute the first description of peptide presentation pathway abnormalities linked to HFE and provide additional evidence for the occurrence of immunologic defects in patients with HH.

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.

Altered expression of CD1d molecules and lipid accumulation in the human hepatoma cell line HepG2 after iron loading

Iron overload in the liver may occur in clinical conditions such as hemochromatosis and nonalcoholic steatohepatitis, and may lead to the deterioration of the normal liver architecture by mechanisms not well understood. Although a relationship between the expression of ICAM-1, and classical major histocompatibility complex (MHC) class I molecules, and iron overload has been reported, no relationship has been identified between iron overload and the expression of unconventional MHC class I molecules. Herein, we report that parameters of iron metabolism were regulated in a coordinated-fashion in a human hepatoma cell line (HepG2 cells) after iron loading, leading to increased cellular oxidative stress and growth retardation. Iron loading of HepG2 cells resulted in increased expression of Nor3.2-reactive CD1d molecules at the plasma membrane. Expression of classical MHC class I and II molecules, ICAM-1 and the epithelial CD8 ligand, gp180 was not significantly affected by iron. Considering that intracellular lipids regulate expression of CD1d at the cell surface, we examined parameters of lipid metabolism in iron-loaded HepG2 cells. Interestingly, increased expression of CD1d molecules by iron-loaded HepG2 cells was associated with increased phosphatidylserine expression in the outer leaflet of the plasma membrane and the presence of many intracellular lipid droplets. These data describe a new relationship between iron loading, lipid accumulation and altered expression of CD1d, an unconventional MHC class I molecule reported to monitor intracellular and plasma membrane lipid metabolism, in the human hepatoma cell line HepG2.

Hemochromatosis Mutations in Iranians with Hepatitis B Virus Infection

In this study, the frequencies of the common hemochromatosis gene mutations were assessed in 75 Iranian subjects with chronic hepatitis B infection. We found that the major C282Y mutation was significantly more frequent in subjects infected with hepatitis B virus (4%) than in 194 control subjects (0%, P=.02; Fisher's exact test).

Growth hormone (GH)-induced reconstitution of CD8+ CD28+ T lymphocytes in a rare case of severe lymphopenia associated with Juvenile Haemochromatosis and Turner's syndrome

This paper describes a rare case of Turner's syndrome associated with Juvenile Haemochromatosis and severe lymphopenia, followed-up for a period of 5 years. Because of the indication for treatment with growth hormone (GH), this case was observed as a model to analyse the effects of GH on growth, iron mobilization and lymphocyte reconstitution. For this purpose, a serial study of the T lymphocyte subpopulations CD4+, CD8+, CD8+ CD28+ and CD8+ CD28- was performed by immunophenotyping during the follow-up period. Besides the impact of both phlebotomy treatment and GH on the rapid growth and mobilization of 20.8 g of iron in 136 weeks, the most relevant observation was the finding of a significant expansion of CD8+ T lymphocytes expressing the costimulatory marker CD28 in the setting of the severe lymphopenia. These findings constitute new clinical evidence supporting the notion that the GH/IGF-1 system has an important role on the maintenance of T cell homeostasis in vivo, and that GH may be regarded as a putative therapeutic agent in T lymphocyte reconstitution.

HFE, the MHC and hemochromatosis: paradigm for an extended function for MHC class I

HFE was discovered as the hereditary hemochromatosis (HH) gene. It is located on chromosome 6 (6p21.3), 4Mb telomeric to the HLA-A locus, and its product has a structure similar to MHC class I molecules. HFE encodes two frequent mutations: C282Y and H63D. One of these (C282Y) is present in a large proportion of Caucasian HH patients. HFE has a tissue distribution compatible with a role in iron absorption (intestine), recycling (macrophages) and transport to the fetus (placenta).

The role of iron in T cell development and autoimmunity

Iron is a vital metal for the proliferation of all cells including those of the immune system. Iron deficiency causes several defects in both the humoral and cellular arms of immunity. One of the most profound changes is a reduction in peripheral T cells and atrophy of the thymus. The presence of transferrin receptor on immature, proliferating thymocytes and the inhibition of thymocyte proliferation and differentiation by anti-transferrin receptor antibody highlight the importance of iron to T cell development. Growing evidence suggests that T cells may in turn, regulate iron metabolism perhaps through interactions with the non-classical major histocompatibility complex gene HFE. The association of the iron transporter NRAMP1 with several autoimmune disorders along with evidence that iron can catalyze the production of cryptic epitopes of several autoantigens, establishes a potential role for iron in the development of autoimmunity.

Peripheral lymphocytes and intracellular cytokines in C282Y homozygous hemochromatosis patients

BACKGROUND/AIMS

Several abnormalities in the immune status of hereditary hemochromatosis patients have been reported. We evaluated the peripheral blood lymphocytes phenotype and cytokine profile of CD8(+) and CD4(+) T cells in C282Y homozygous hereditary hemochromatosis patients compared to control subjects.

METHODS

Peripheral blood lymphocytes from 17 asymptomatic patients and 14 control subjects were analyzed. We determined the distribution of lymphocyte subsets and investigated at single-cell level by flow-cytometry the potential of cytokines production. The frequency of cytokine (interferon gamma, tumor necrosis factor alpha, interleukin 2 (IL-2), IL-4, IL-5, IL-10 and IL-13) producing cells was assessed in total T-lymphocytes, CD3(+)CD8(+) and CD3(+)CD4(+) subsets.

RESULTS

The patients studied showed a significant decrease of total lymphocyte count, T CD4(+)CD3(+), CD28(+), CD8(+)CD28(+) lymphocytes and natural killer (NK) CD56(+)CD16(+)CD3(-) cells. The reduction of CD28(+) and CD8(+)CD28(+) lymphocyte count was inversely related to transferrin saturation index. An increase in the ability of T-cells to produce all the cytokines studied and a major increase in IL-4 and IL-10 production in the CD3(+)CD8(+) subset was found. Our results demonstrate that activated Th1 and Th2 lymphocytes coexist in the peripheral blood of hereditary hemochromatosis patients and that T-cytotoxic (Tc) 2 subset is more expanded than in control population.

CONCLUSIONS

The association of a decreased number of T CD8(+) cytotoxic lymphocytes and NK cells, and the development of Tc2 cells in asymptomatic C282Y homozygous patients represents an imbalance in their immune function that might contribute to the high incidence of hepatocarcinoma.

Generation of monocyte-derived dendritic cells in patients with hereditary hemochromatosis

Hereditary hemochromatosis (HH) is a common genetic disease with autosomal recessive transmission and is characterized by a dysregulation of iron metabolism, leading to serum iron overload and its progressive accumulation in most body tissues. The effects of HH on the immune system include altered lymphocytosis and functions of monocytes. Moreover, monocytes can differentiate into dendritic cells (DCs), which play crucial roles in the immune response (capture, processing, and presentation of antigen to effector T cells) and this process was shown to be impaired in several pathologies. The aim of this study was to determine whether the monocytes from HH patients still displayed the ability to differentiate into DCs. To that purpose, purified monocytes from healthy donors and HH patients were cultured in the appropriate medium. The results showed no phenotypic and functional differences, at both the immature and the mature stages. Furthermore, our work reports altered lymphocytosis with expanded CD8+CD28- T cell subset. These monocyte-derived DCs could therefore be a solid vector for DC-based immunotherapy and a powerful tool for investigating the immune regulatory loops and especially the biological relevance of the expanded CD8+CD28- T cells since this population has also been described as suppressor T cells.

Human red blood cells have an enhancing effect on the relative expansion of CD8+ T lymphocytes in vitro

The present study was designed to analyse the effect of red blood cells on T-cell proliferation and expansion. A comparative study was done in peripheral blood cell cultures stimulated with phytohemagglutinin, with or without red blood cells. The presence of red blood cells had a consistent enhancing effect on T lymphocyte proliferation, as determined by an increase in both the mitotic index and thymidine uptake. Phenotypic characterization of T cell blasts by flow cytometry revealed that, in the presence of red blood cells, expanding cells were preferentially CD8+ cells. Accordingly, proliferation of CD8+ lymphocytes from two patients with CD8+ hyperlymphocytosis was dependent on the presence of red blood cells. In contrast, proliferation of CD4+ lymphocytes from two patients with CD4+ hyperlymphocytosis was strongly inhibited by the presence of red blood cells. This is the first reported evidence that human red blood cells have an enhancing effect on the expansion of CD8+ lymphocytes in vitro.

Hemochromatosis gene in leukemia and lymphoma

The gene causing hereditary hemochromatosis (HH), HFE is an HLA class I-like gene with no known immunological function but indirectly related to the immune functions because of its role in iron transport. It is located 6.5 Mb telomeric to HLA-A. The most common mutation of HFE, C282Y, has a Celtic origin and most patients with HH are homozygous for it in Northern European populations. While there is an enormously increased risk for hepatocellular cancer in hemochromatosis that is attributed to the toxic effects of iron, the risk for extra-hepatic cancers is also increased slightly. Recent studies have found genetic associations between several cancers and C282Y but only in the presence of a particular allele of the transferrin receptor gene. This suggests that the increased cancer risk is more likely due to the effects of iron. In childhood acute lymphoblastic leukemia (ALL), however, there is a strong association of C282Y with a gender effect in two different Celtic populations. This association does not require homozygosity for C282Y or an interaction with the transferrin receptor gene, and is male-specific. The other HFE mutation H63D does not confer increased risk to childhood ALL. Acute myeloblastic leukemia and Hodgkin's disease in adults do not have an association with HFE. Its male-specificity, occurrence in childhood and the lack of a gene-dosage effect suggest that the C282Y association in childhood ALL may reflect the involvement of another HLA-linked gene in leukemia susceptibility.

CD8+CD28- T cells: certainties and uncertainties of a prevalent human T-cell subset

Human peripheral blood CD8+ T cells comprise cells that are in different states of differentiation and under the control of complex homeostatic processes. In a number of situations ranging from chronic inflammatory conditions and infectious diseases to ageing, immunodeficiency, iron overload and heavy alcohol intake, major phenotypic changes, usually associated with an increase in CD8+ T cells lacking CD28 expression, take place. CD8+CD28- T cells are characterized by a low proliferative capacity to conventional stimulation in vitro and by morphological and functional features of activated/memory T cells. Although the nature of the signals that give origin to this T-cell subset is uncertain, growing evidence argues for the existence of an interplay between epithelial cells, molecules with the MHC-class I fold and CD8+ T cells. The possibility that the generation of CD8+CD28- T cells is the combination of TCR/CD3zeta- and regulatory factor-mediated signals as a result of the sensing of modifications of the internal environment is discussed.

Association between Cys282Tyr missense mutation and haptoglobin phenotype polymorphism in patients with chronic hepatitis C

INTRODUCTION

In patients with chronic hepatitis C infection, the haptoglobin (Hp) 1-1 phenotype is overrepresented. Data regarding the occurrence of the Cys282Tyr missense mutation in these patients are less clear. We studied the prevalence of both variables in a cohort of patients with chronic hepatitis C and looked for interaction between the two variables.

MATERIALS AND METHODS

The study group consisted of 142 patients chronically infected with the hepatitis C virus. All patients were examined for the occurrence of the Cys282Tyr missense mutation, and in 132 of them the Hp phenotype was determined. The Cys282Tyr missense mutation was detected by restriction fragment length polymorphism (RFLP) using a standard polymerase chain reaction (PCR) technique and RsaI digestion. Hp phenotypes were determined using starch gel electrophoresis of haemoglobin-supplemented serum followed by peroxidase staining.

RESULTS

A significant overrepresentation of the Hp 1-1 phenotype was found (36/132, 27%, P < 0.01 v. control population). This overrepresentation was observed only in the patients homozygous for the wild-type allele of the HFE gene. The Cys282Tyr allele was significantly overrepresented in hepatitis C patients (0.12 v. 0.07, P < 0.05) and principally in patients with the Hp 2-1 and 2-2 phenotypes.

CONCLUSION

In patients with chronic hepatitis C infection, both the Hp 1-1 and the Cys282Tyr allele occur more frequently than in a control population. Remarkably, these genes seem to determine each other's occurrence, such that the overrepresentation of the Hp 1-1 phenotype is seen only in Cys282Tyr-negative subjects, while the overrepresentation of the Cys282Tyr allele is observed in Hp 1-1-negative subjects. Differences in immunomodulating and in oxidative stress-inducing capacities between the two genes may explain this finding.

Clinical and genetic heterogeneity in hereditary haemochromatosis: association between lymphocyte counts and expression of iron overload

To identify a new marker of expression of disease, independent of HFE genotype in patients with hereditary haemochromatosis (HHC), the total peripheral blood lymphocyte counts were analysed according to iron status in two groups of subjects with HFE mutations. The groups consisted of 38 homozygotes for C282Y, and 107 heterozygotes for the C282Y or compound heterozygotes for C282Y and H63D. For control purposes, total lymphocyte counts and iron status were also examined in 20 index patients with African dietary iron overload, a condition not associated with HFE mutations, and in 144 members of their families and communities. Mean lymphocyte numbers were lower in C282Y homozygous HHC index subjects with cirrhosis and higher iron stores than in those without cirrhosis and with lower iron burdens [(1.65 +/- 0.43) x 10(6)/mL vs. (2.27 +/- 0.49) x 10(6)/mL; p = 0.008]. Similarly, mean lymphocyte counts were significantly lower in C282Y heterozygotes and C282Y/H63D compound heterozygotes with iron overload and increased serum ferritin concentrations compared to those with normal serum ferritin concentrations (p < 0.05). Statistically significant negative correlations were found, in males, between lymphocyte counts and the total body iron stores, either in C282Y homozygous HHC patients (p = 0.031 in a multiple regression model dependent on age) and in C282Y heterozygotes or C282Y/H63D compound heterozygotes with iron overload (p = 0.029 in a simple linear model). In contrast, lymphocyte counts increased with increasing serum ferritin concentrations among the index subjects with African iron overload (r = 0.324, not statistically significant) and among the members of their families and communities (r = 0.170, p = 0.042). These results suggest that a lower peripheral blood lymphocyte count is associated with a greater degree of iron loading in HFE haemochromatosis but not in African iron overload, and they support the notion that the lymphocyte count may serve as a marker of a non-HFE gene that influences the clinical expression of HFE haemochromatosis.

T-cell receptor repertoire in hereditary hemochromatosis: a study of 32 hemochromatosis patients and 274 healthy subjects

Low CD8(+) T lymphocyte numbers have contributed to deciphering the genotype/phenotype discrepancies found in hereditary hemochromatosis (HH) patients genotyped for the Hfe mutations, C282Y and H63D. In this study, we extend the analysis of T lymphocytes in HH to the T cell receptor (TcR) repertoire. Thirty-two HH patients (C282Y homozygous) and 274 Hfe genotyped healthy subjects were studied. The following TcR chains were analyzed: Valpha2.3, Vbeta5.1, Vbeta5.2, Vbeta5.3, Vbeta6.7, Vbeta8, and Vbeta12 among the CD4(+) and CD8(+) populations. Lymphopenias and absence of expansions of the Vbeta5.2 and Vbeta12 chains in the CD8(+) pool were seen in controls heterozygous for the C282Y mutation. Expansions in the control group were seen within the CD8(+) pool and were rare/absent within the CD4(+) pool. TcR expansions were found more frequent in patients with iron overload related pathology than in patients without pathology. 9/16 of the patients with pathology have at least one expansion among the CD8(+) pool a number significantly higher compared with patients without pathology (1/16). These findings suggest that Hfe has an effect in the shaping of T-cell populations either directly, as indicated by the lymphopenia seen in the two chains in C282Y heterozygous without iron overload, or indirectly by contributing to iron overload pathology.

The major histocompatibility complex-encoded HFE in iron homeostasis and immune function

HFE is a non-classical major histocompatibility complex class I molecule that complexes with a beta2-microglobulin. A functional link between HFE and iron metabolism has been established by the discovery of a physical association between HFE and the transferrin receptor. By inhibiting transferrin receptor internalization, HFE functions as a negative modulator of transferrin receptor function. In addition, HFE appears to be an iron sensor that directly or indirectly communicates the body's iron status to T cells, which then use cytokines as feedback modulators to achieve iron homeostasis. A working model for the feedback regulatory mechanism between iron metabolism and immune function is proposed.

Hepatic damage in C282Y homozygotes relates to low numbers of CD8+ cells in the liver lobuli

BACKGROUND

Although most Caucasian patients with hereditary haemochromatosis (HH) show the same mutation in the HFE gene, the phenotypic expression of the disease varies greatly. We have previously shown that patients with HH who have high iron stores have low numbers of circulating CD8+ T lymphocytes.

PATIENTS AND METHODS

Liver and peripheral blood were studied in 37 C282Y homozygous HH patients; nine normal livers and 11 livers from patients with cirrhosis due to hepatitis C virus or alcoholic liver disease were also investigated. Eleven jejunal biopsies from HH patients and 17 normal biopsies were studied. The numbers of CD8+ cells were determined in peripheral blood by fluorescence-activated cell sorting analysis, and in the liver or small intestine by immunohistochemistry.

RESULTS

In HH patients the number of CD8+ T lymphocytes in peripheral blood correlated significantly with the number of CD8+ cells in the liver lobuli but not with that in the small intestine. Body iron stores correlated negatively with the number of CD8+ T lymphocytes in peripheral blood and in the liver, but not with the number in the small intestine. HH patients with cirrhosis had the lowest CD8+ cell count in liver sections, in contrast with other forms of cirrhosis.

CONCLUSION

The results indicate that HH patients with the HFE C282Y mutation and low numbers of CD8+ cells in the liver lobuli have higher iron stores and are more prone to develop liver cirrhosis.

Regulation of intracellular iron levels in iron-acceptor and iron-donor cells

In recent years many new genes and proteins were identified with crucial functions in iron metabolism. This gave an explosion of our knowledge and understanding of iron related disorders. Mutations have been found that are responsible for disturbances in iron transport, leading to either iron overload or iron deficiency. For experts in the field, these new findings clarify the sky and open new routes for exploring hitherto hidden fields of research. For the physician, however, iron metabolism may become even more complicated. In this review, we have tried to assemble all new iron related genes into the context of pathophysiology. Important results from animal experiments, mainly derived from knockout mouse models, are included in this review as they often explain the phenotype of human disease.

Iron overload and heart fibrosis in mice deficient for both beta2-microglobulin and Rag1

Genetic causes of hereditary hemochromatosis (HH) include mutations in the HFE gene, a ss2-microglobulin (ss2m)-associated major histocompatibility complex class I-like protein. Accordingly, mutant ss2m(-/-) mice have increased intestinal iron absorption and develop parenchymal iron overload in the liver. In humans, other genetic and environmental factors have been suggested to influence the pathology and severity of HH. Previously, an association has been reported between low numbers of lymphocytes and the severity of clinical expression of the iron overload in HH. In the present study, the effect of a total absence of lymphocytes on iron overload was investigated by crossing ss2m(-/-) mice (which develop iron overload resembling human disease) with mice deficient in recombinase activator gene 1 (Rag1), which is required for normal B and T lymphocyte development. Iron overload was more severe in ss2mRag1 double-deficient mice than in each of the single deficient mice, with iron accumulation in parenchymal cells of the liver, in acinar cells of the pancreas, and in heart myocytes. With increasing age ss2mRag1(-/-) mice develop extensive heart fibrosis, which could be prevented by reconstitution with normal hematopoietic cells. Thus, the development of iron-mediated cellular damage is substantially enhanced when a Rag1 mutation, which causes a lack of mature lymphocytes, is introduced into ss2m(-/-) mice. Mice deficient in ss2m and Rag1 thus offer a new experimental model of iron-related cardiomyopathy.

Expansions of CD8+CD28- and CD8+TcRVbeta5.2+ T cells in peripheral blood of heavy alcohol drinkers

BACKGROUND

Despite heavy alcohol consumption, only a low percentage of heavy drinkers develop liver disease. Imbalances in T-cell subsets and iron metabolism parameters are common findings in heavy drinkers, yet the possible role played by discrete T-lymphocyte subsets under heavy alcohol consumption remains unclear.

METHODS

To gain new insights into the possible role played by T lymphocytes during alcohol consumption, characterization of CD28 expression and TcR repertoire in peripheral blood CD4+ and CD8+ T cells by two and three-color flow cytometry was performed. A group of heavy alcohol drinkers (AHD, n = 71) and a group of age-matched controls (n = 81), both HLA-phenotyped and HFE-genotyped, constituted the groups under study.

RESULTS

Marked expansions of CD28- T cells within the CD8+ but not the CD4+ T-cell pool were observed in AHD compared with controls. These CD8+CD28- expansions were paralleled by expansions of CD8+ T cells bearing specific TcR Valpha/beta chains, namely VP5.2. Moreover, AHD, but not controls, carrying the H63D mutation in the HFE gene showed significantly higher percentages of CD28- T cells within the CD8+ T-cell pool than AHD carrying the normal HFE gene. Finally, high numbers of CD8+CD28- T cells in AHD were associated with lower levels of the liver-related enzymes ALT and GGT.

CONCLUSIONS

This study showed that under active ethanol consumption, expansions of discrete CD8+ T-cell subsets occur within the CD8+ T-cell pool, that molecules of the MHC-class I locus seem to influence the extent of the expansions, and that high numbers of CD8+CD28- T cells are associated with low levels of liver enzymes in AHD.