The TNF2 allele is a risk factor to severe aplastic anemia independent of HLA-DR

Hodgkin lymphoma patients have an increased incidence of idiopathic acquired aplastic anemia

Idiopathic acquired aplastic anemia (AA) is a rare lymphocyte-mediated bone marrow aplasia. No specific mechanisms or triggers of AA have been identified. We recently observed several patients who developed AA after Hodgkin lymphoma (HL). We hypothesized that the co-occurrence of HL and AA is not random and may be etiologically significant. To test this hypothesis, we determined the incidence of AA in HL patients at our institution. We identified four patients with co-occurring HL and AA, with the incidence of AA in HL patients >20-fold higher compared to the general population. We identified 12 additional patients with AA and HL through a systematic literature review. Of the 16 total patients,15 (93.8%) developed AA after or concurrent with a HL diagnosis. None of the patients had marrow involvement by HL. Five of 15 patients were in complete remission from HL at the time of AA diagnosis, and six had a concurrent presentation with no prior cytotoxic therapy, with diagnostic timeframe information unavailable for four patients. The median interval between HL diagnosis and AA onset was 16 months, ranging from concurrent to 14 years after a HL diagnosis. The median survival after AA diagnosis was 14 months (range: 1 month to 20 years). Our results show that patients with HL have a higher incidence of AA compared to the general population and suggest that HL-related immune dysregulation may be a risk factor for AA. Better recognition and management of AA in HL patients is needed to improve outcomes in this population.

The Pathophysiology of Acquired Aplastic Anemia: Current Concepts Revisited

Idiopathic acquired aplastic anemia is a rare, life-threatening bone marrow failure syndrome characterized by cytopenias and hypocellular bone marrow. The pathophysiology is unknown; the most favored model is of a dysregulated immune system leading to autoreactive T-cell destruction of hematopoietic stem and progenitor cells in a genetically susceptible host. The authors review the literature and propose that the major driver of acquired aplastic anemia is a combination of hematopoietic stem and progenitor cells intrinsic defects and an inappropriately activated immune response in the setting of a viral infection. Alterations in bone marrow microenvironment may also contribute to the disease process.

The association of cytokine genes polymorphisms and susceptibility to aplastic anemia in Egyptian patients

BACKGROUND AND OBJECTIVE

Aplastic anemia (AA) remains a rare disease, with very interesting pathophysiology that is being investigated for years now. The present study aimed to determine the association between cytokine gene polymorphisms (TGF-β1 -509 C/T, TNF-α -308 G/A, IFN-γ +874 A/T) and susceptibility to AA in Egyptian patients.

METHODS

The study included 80 participants subjected to determination of gene polymorphisms on genomic DNA using polymerase chain reaction-restriction fragment length polymorphism assay.

RESULTS

It was found that IFN-γ +874 A/T gene polymorphism is associated with three-fold increased risk of development of AA (odds ratio (OR) 3.116, P = 0.019), while TNF-α -308 G/A gene polymorphism is associated with decreased risk (OR 0.318, P = 0.026). TGF-β1 -509 C/T gene polymorphism showed comparable risk between patients and controls (P = 0.263).

CONCLUSION

IFN-γ +874 A/T gene polymorphism is associated with the etiology of AA in Egyptian patients.

The complex pathophysiology of acquired aplastic anaemia

Immune-mediated destruction of haematopoietic stem/progenitor cells (HSPCs) plays a central role in the pathophysiology of acquired aplastic anaemia (aAA). Dysregulated CD8(+) cytotoxic T cells, CD4(+) T cells including T helper type 1 (Th1), Th2, regulatory T cells and Th17 cells, natural killer (NK) cells and NK T cells, along with the abnormal production of cytokines including interferon (IFN)-γ, tumour necrosis factor (TNF)-α and transforming growth factor (TGF)-β, induce apoptosis of HSPCs, constituting a consistent and defining feature of severe aAA. Alterations in the polymorphisms of TGF-β, IFN-γ and TNF-α genes, as well as certain human leucocyte antigen (HLA) alleles, may account for the propensity to immune-mediated killing of HSPCs and/or ineffective haematopoiesis. Although the inciting autoantigens remain elusive, autoantibodies are often detected in the serum. In addition, recent studies provide genetic and molecular evidence that intrinsic and/or secondary deficits in HSPCs and bone marrow mesenchymal stem cells may underlie the development of bone marrow failure.

TNF-α -308 G>A polymorphism and risk of bone marrow failure syndrome: A meta-analysis

The influence of the TNF-α -308 G>A polymorphism on bone marrow failure syndrome susceptibility is unclear. We have conducted a meta-analysis of all relevant published studies. We searched PubMed, Chinese Biomedical Literature and China National Knowledge Infrastructure databases up to February 2015. Odds ratios (ORs) with 95% confidence intervals (CIs) were applied to assess the strength of associations. Eleven case-control studies with a total sample size of 909 cases and 1803 controls were eligible to assess the association between the TNF-α -308 G>A polymorphism and susceptibility to bone marrow failure syndrome. Overall, the TNF-α -308 G>A polymorphism was significantly associated with an increased risk of bone marrow failure syndrome in any genetic model. In stratified analysis by disease type, there was a significant association between the TNF-α -308 G>A polymorphism and increased risk of aplastic anemia but no significant association with myelodysplastic syndrome (AA vs. GG: OR=2.23, 95% CI=1.23-4.05, P=0.006; recessive model: OR=3.52, 95% CI=1.30-9.53, P=0.010). In subgroup analysis by ethnicity, there were significant associations between the TNF-α -308 G>A polymorphism and increased risk of bone marrow failure syndrome for Caucasians in two models, but not in Asian populations (AA vs. GG: OR=2.66, 95% CI=1.36-5.21, P=0.003; recessive model: OR=2.68, 95% CI=1.37-5.24, P=0.002). In conclusion, our meta-analysis suggests that the TNF-α -308 G>A polymorphism may contribute to the risk of bone marrow failure syndrome, particularly among Caucasian and aplastic anemia patients. Further investigations are needed to clarify the role of the TNF-α -308 G>A polymorphism in bone marrow failure syndrome.

Immunoregulatory cytokines gene polymorphisms in Egyptian patients affected with acquired aplastic anemia

The immune system is thought to play an important role in aplastic anemia (AA) in light of recent findings of hematologic reconstitution after immunosuppressive therapy. T cell activation, apoptosis, and the cytokines interferon- and TNF-α are suspected to play a role in the suppression of growth of progenitor cells and induced apoptosis in CD34 target cells, TGFβ is a multifunctional peptide, usually produced in latent form and requiring activation to produce a biological response. Also, TGF-β1 has been described as an important negative regulator of haemopoiesis. Over production of IL-6 is described in AA but is of unknown pathophysiological significance. To investigate the role of cytokine gene polymorphisms (IL-6/-174, TNF-α/-308, IFN-γ/+874, and TGFβ1/-509) in patients with acquired AA to assess if genotypes associated with higher or lower production were more prevalent than in established control population and to study the possible association of these genotypes with the disease severity. Fifty AA patients were included in this study. Polymerase chain reaction-amplification refractory mutation system (PCR-ARMS) technique was used to detect INF-γ single nucleotide polymorphism -874A/T, and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to assess IL-6-174 C/G, TNF-α-308G/A, and TGFb1-509C/T gene polymorphisms. Genotypes associated with high production of TNF-α, TGF-β and IFN-γ, and IL-6 were more frequent in patients than in control; no association was found between the presence of hypersecretory genotypes and the disease severity.

Common polymorphic deletion of glutathione S-transferase theta predisposes to acquired aplastic anemia: Independent cohort and meta-analysis of 609 patients

Acquired aplastic anemia (AA) is a rare life-threatening bone marrow failure syndrome, caused by autoimmune destruction of hematopoietic stem and progenitor cells. Epidemiologic studies suggest that environmental exposures and metabolic gene polymorphisms contribute to disease pathogenesis. Several case-control studies linked homozygous deletion of the glutathione S-transferase theta (GSTT1) gene to AA; however, the role of GSTT1 deletion remains controversial as other studies failed to confirm the association. We asked whether a more precise relationship between the GSTT1 null polymorphism and aplastic anemia could be defined using a meta-analysis of 609 aplastic anemia patients, including an independent cohort of 67 patients from our institution. We searched PubMed, Embase, and the Cochrane Database for studies evaluating the association between GSTT1 null genotype and development of AA. Seven studies, involving a total of 609 patients and 3,914 controls, fulfilled the eligibility criteria. Meta-analysis revealed a significant association of GSTT1 null genotype and AA, with an OR = 1.74 (95% CI 1.31-2.31, P < 0.0001). The effect was not driven by any one individual result, nor was there evidence of significant publication bias. The association between AA and GSTT1 deletion suggests a role of glutathione-conjugation in AA, possibly through protecting the hematopoietic compartment from endogenous metabolites or environmental exposures. We propose a model whereby protein adducts generated by reactive metabolites serve as neo-epitopes to trigger autoimmunity in aplastic anemia.

Genetic associations in acquired immune-mediated bone marrow failure syndromes: insights in aplastic anemia and chronic idiopathic neutropenia

Increasing interest on the field of autoimmune diseases has unveiled a plethora of genetic factors that predispose to these diseases. However, in immune-mediated bone marrow failure syndromes, such as acquired aplastic anemia and chronic idiopathic neutropenia, in which the pathophysiology results from a myelosuppressive bone marrow microenvironment mainly due to the presence of activated T lymphocytes, leading to the accelerated apoptotic death of the hematopoietic stem and progenitor cells, such genetic associations have been very limited. Various alleles and haplotypes of human leucocyte antigen (HLA) molecules have been implicated in the predisposition of developing the above diseases, as well as polymorphisms of inhibitory cytokines such as interferon-γ, tumor necrosis factor-α, and transforming growth factor-β1 along with polymorphisms on molecules of the immune system including the T-bet transcription factor and signal transducers and activators of transcription. In some cases, specific polymorphisms have been implicated in the outcome of treatment on those patients.

The genetics and clinical manifestations of telomere biology disorders

Telomere biology disorders are a complex set of illnesses defined by the presence of very short telomeres. Individuals with classic dyskeratosis congenita have the most severe phenotype, characterized by the triad of nail dystrophy, abnormal skin pigmentation, and oral leukoplakia. More significantly, these individuals are at very high risk of bone marrow failure, cancer, and pulmonary fibrosis. A mutation in one of six different telomere biology genes can be identified in 50–60% of these individuals. DKC1, TERC, TERT, NOP10, and NHP2 encode components of telomerase or a telomerase-associated factor and TINF2, a telomeric protein. Progressively shorter telomeres are inherited from generation to generation in autosomal dominant dyskeratosis congenita, resulting in disease anticipation. Up to 10% of individuals with apparently acquired aplastic anemia or idiopathic pulmonary fibrosis also have short telomeres and mutations in TERC or TERT. Similar findings have been seen in individuals with liver fibrosis or acute myelogenous leukemia. This report reviews basic aspects of telomere biology and telomere length measurement, and the clinical and genetic features of those disorders that constitute our current understanding of the spectrum of illness caused by defects in telomere biology. We also suggest a grouping schema for the telomere disorders.

Impact of cytokine gene polymorphisms on risk and treatment outcomes of aplastic anemia

Autoreactive cytotoxic T cells play a key role in the pathogenesis of aplastic anemia (AA) by myelosuppressive cytokines including interferon-gamma, tumor necrosis factor alpha, and transforming growth factor beta. The purpose of this study is to determine which single nucleotide polymorphisms (SNPs) in cytokine genes were relevant to AA risk and whether the relevant SNPs were associated with response to immunosuppressive therapy (IST). Among 84 screened patients, 80 patients confirmed as having acquired AA, and 84 age- and sex-matched healthy controls were analyzed consecutively. We genotyped ten polymorphisms in three cytokine genes (IFNG, TNF, and TGFB1) and FAS gene. We assessed the association between polymorphisms and AA risk, and the association between polymorphisms and response to IST in three genetic models (dominant, recessive, and additive). The IFNG -2,353 T allele (dominant model, OR = 0.43, p = .012) and TCA haplotype (dominant model, OR = 0.50, p = .038) were significantly associated with the development of AA. In addition, this relevant IFNG -2,353 T allele and TCA haplotype were related to the response of IST (dominant model, OR = 0.076, p = .034). Concerning TGFB1, although its polymorphisms are not related to AA susceptibility, P10L T allele (recessive model, OR = 0.18, p = .038) and CT haplotype (dominant model, OR = 5.68, p = .038) were associated with response to IST. This exploratory study concurred with prior studies indicating that polymorphisms in IFNG are related to AA susceptibility. In addition, it was found that polymorphisms in IFNG and TGFB1 are associated with response to IST.

Aplastica anemia and viral hepatitis

Acquired aplastic anemia (aAA) is a severe and rare disease, characterized by hematopoietic bone marrow failure and peripheral cytopenia. The pathophysiology is immune mediated in most cases, activated T1 lymphocytes have been identified as effector cells. The disease can be successfully treated with combined immunosuppressive therapy or allogeneic hematopoietic stem cell transplantation. Hepatitis-associated aplastic anemia (HAA) is a syndrome of bone marrow failure following the development of acute seronegative hepatitis. HAA syndrome most often affects young males who presented severe pancytopenia two to three months after an episode of acute hepatitis. The clinical course of hepatitis is more frequently benign but a fulminant severe course is also described. The bone marrow failure can be explosive and severe and it is usually fatal if untreated, no correlations have been observed between severity of hepatitis and AA. In none of the studies a specific virus could be identified and most cases are seronegative for known hepatitis viruses. The clinical characteristics and response to immunotherapy indicate a central role for immune-mediated mechanism in the pathogenesis of HAA. The initial target organ of the immune response is the liver as suggested by the time interval between hepatitis and the onset of bone marrow failure. Liver histology is characterized by T cell infiltrating the parenchyma as reported in acute hepatitis. Recently in HAA it has been demonstrated intrahepatic and blood lymphocytes with T cell repertoire similar to that of confirmed viral acute hepatitis. The expanded T cell clones return to a normal distribution after response to immunosuppressive treatment, suggesting the antigen or T cell clearance. Therapeutic options are the same as acquired aplastic anemia.

The role of telomere biology in bone marrow failure and other disorders

Telomeres, consisting of nucleotide repeats and a protein complex at chromosome ends, are essential in maintaining chromosomal integrity. Dyskeratosis congenita (DC) is the inherited bone marrow failure syndrome (IBMFS) that epitomizes the effects of abnormal telomere biology. Patients with DC have extremely short telomere lengths (<1st percentile) and many have mutations in telomere biology genes. Interpretation of telomere length in other IBMFSs is less straightforward. Abnormal telomere shortening has been reported in patients with apparently acquired hematologic disorders, including aplastic anemia, myeolodysplasia, paroxysmal nocturnal hemoglobinuria, and leukemia. In these disorders, the shortest-lived cells have the shortest telomeres, suggestive of increased hematopoietic stress. Telomeres are also markers of replicative and/or oxidative stress in other complex disease pathways, such as inflammation, stress, and carcinogenesis. The spectrum of related disorders caused by mutations in telomere biology genes extends beyond classical DC to include marrow failure that does not respond to immunosuppression, idiopathic pulmonary fibrosis, and possibly other syndromes. We suggest that such patients be categorized as having an inherited disorder of telomere biology. Longitudinal studies of patients with very short telomeres but without classical DC are necessary to further understand the long-term sequelae, such as malignancy, osteonecrosis/osteoporosis, and pulmonary and liver disease.

Autoimmunity and malignancy in hematology—More than an association

Several associations between hematological malignancies and autoimmunity directed against hematopoietic cells exist. Antibody mediated elimination of mature blood cells such as autoimmune hemolytic anemia (AIHA) and immune thrombocytopenia (ITP) are frequent complications of non-Hodgkin lymphomas, most prominently chronic lymphocytic leukemia. Autoimmunity directed against hematopoietic precursor cells is the hallmark of aplastic anemia, but many features of this disease are shared by two related disorders, paroxysmal nocturnal hemoglobinuria (PNH) and myelodysplastic syndrome (MDS). While the clinical associations between hematological malignancy and autoimmunity have been described many decades ago, only in the last several years have the common pathogenetic mechanisms been elucidated. We summarize the recent progress made in understanding how hematological malignancy gives rise to autoimmunity directed against blood cells and vice versa, and illustrate parallels in the etiology of malignant and autoimmune hematological disorders. Specifically, recent progress in the recognition of the association of lymphoproliferative disorders and autoimmunity against mature blood cells, and common pathogenetic background of aplastic anemia, paroxysmal nocturnal hemoglobinuria, and myelodysplastic syndrome are discussed.

Polymorphisms of TNF microsatellite marker a and HLA-DR-DQ in diabetes mellitus—a study in 609 Swedish subjects

We explored the importance of the genetic markers microsatellite TNFa, HLA-DR3-DQ2, and DR4-DQ8 in diabetes mellitus. The studied groups comprised autoimmune type 1 (n = 63), nonautoimmune type 1 (n = 35), latent autoimmune diabetes in adults (LADA; n = 54), and nonautoimmune type 2 (n = 340) and these patients were compared to 117 healthy controls. HLA genotyping was done with polymerase chain reaction and sequence-specific oligonucleotides. TNFa microsatellites were determined with polymerase chain reaction and fragment size determination. Univariate analysis of these genetic risk factors demonstrated that homozygosity for TNFa2/2 was a significant risk factor for autoimmune type 1 diabetes (odds ratio (OR) = 5.82; 95% confidence interval (95%CI) 1.97-17.2), for autoimmune negative type 1 diabetes (OR = 4.63; 95%CI 1.32-16.2), and for LADA (OR = 3.90; 95%CI 1.21-12.5). Moreover, heterozygosity for HLA-DR3-DQ2/DR4-DQ8 was an important risk factor for autoimmune type 1 diabetes (OR = 16.4; 95%CI 3.60-75) as was DR4-DQ8/x (OR = 2.52; 95%CI 1.27-4.98). Heterozygosity for HLA-DR3-DQ2/DR4-DQ8 was a risk factor also for LADA (OR = 10.0; 95%CI 2.05-48.9). Neither HLA-DR3-DQ2 nor DR4-DQ8 were risk factors for nonautoimmune type 1 or type 2 diabetes. We concluded that heterozygosity for DR3-DQ2/DR4-DQ8 and to some extent homozygosity for TNFa2/2 were risk factors for autoimmune diabetes irrespective of the clinical classification.

Current concepts in the pathophysiology and treatment of aplastic anemia

Aplastic anemia, an unusual hematologic disease, is the paradigm of the human bone marrow failure syndromes. Almost universally fatal just a few decades ago, aplastic anemia can now be cured or ameliorated by stem-cell transplantation or immunosuppressive drug therapy. The pathophysiology is immune mediated in most cases, with activated type 1 cytotoxic T cells implicated. The molecular basis of the aberrant immune response and deficiencies in hematopoietic cells is now being defined genetically; examples are telomere repair gene mutations in the target cells and dysregulated T-cell activation pathways. Immunosuppression with antithymocyte globulins and cyclosporine is effective at restoring blood-cell production in the majority of patients, but relapse and especially evolution of clonal hematologic diseases remain problematic. Allogeneic stem-cell transplant from histocompatible sibling donors is curative in the great majority of young patients with severe aplastic anemia; the major challenges are extending the benefits of transplantation to patients who are older or who lack family donors. Recent results with alternative sources of stem cells and a variety of conditioning regimens to achieve their engraftment have been promising, with survival in small pediatric case series rivaling conventional transplantation results.

Relative incidence of agranulocytosis and aplastic anemia

Agranulocytosis and aplastic anemia are both rare, life-threatening blood dyscrasias. Agranulocytosis is mainly caused by medicines, whereas the etiology of aplastic anemia is largely unexplained. In two epidemiologic studies using the same methods, we observed a striking inverse relationship between the incidence of the two diseases in different regions, including five countries in Europe, and Israel and Thailand. The annual incidence of agranulocytosis ranged from 1.1 to 4.9 cases per million, and that of aplastic anemia, from 0.7 to 4.1 per million; the inverse correlation was consistent among the regions (R2 = 0.74). There is no clear explanation for this previously unreported pattern, but it seems unlikely to be due to methodology.

Pathophysiologic mechanisms in acquired aplastic anemia

Aplastic anemia, an unusual hematologic disease, is the paradigm of the human bone marrow failure syndromes. Absence of hematopoietic cells has been recognized from the characteristic morphology for a century; an immune pathophysiology has been inferred from improvement in blood counts with immunosuppressive therapy in the majority of patients. Molecular mechanisms underlying both T cell effector cells and the target marrow stem and progenitor cells are now being identified. Activated type 1 cytotoxic T cells and type 1 cytokines have been implicated in cell culture experiments; clues to the molecular basis of the aberrant immune response include cytokine gene polymorphisms and abnormalities in the regulatory pathways for gamma-interferon. For stem cell depletion, mutations in genes of the telomere repair complex are present in some patients with apparently acquired aplastic anemia. Telomerase deficiency is associated with short telomeres and a quantitative reduction in marrow progenitors and likely also a qualitative deficiency in the repair capacity of hematopoietic tissue.

Mutations in TERT, the gene for telomerase reverse transcriptase, in aplastic anemia

BACKGROUND

Mutations in TERC, the gene for the RNA component of telomerase, cause short telomeres in congenital aplastic anemia and in some cases of apparently acquired hematopoietic failure. We investigated whether mutations in genes for other components of telomerase also occur in aplastic anemia.

METHODS

We screened blood or marrow cells from 124 patients with apparently acquired aplastic anemia and 282 control subjects for sequence variations in the TERT, DKC1, NHP2, and NOP10 genes; an additional 81 patients and 246 controls were examined for genetic variations in TERT. Telomere lengths and the telomerase activity of peripheral-blood leukocytes were evaluated in patients carrying genetic variants. Identified mutations were transfected into telomerase-deficient cell lines to examine their effects and their mechanism of action on telomerase function.

RESULTS

Five heterozygous, nonsynonymous mutations (which cause an amino acid change in the corresponding protein) were identified in TERT, the gene for the telomerase reverse transcriptase catalytic enzyme, among seven unrelated patients. Leukocytes from these patients had short telomeres and low telomerase enzymatic activity. In three of these patients, the mutation was also detected in buccal mucosa cells. Family members carrying the mutations also had short telomeres and reduced telomerase activity but no evident hematologic abnormality. The results of coexpression of wild-type TERT and TERT with aplastic anemia-associated mutations in a telomerase-deficient cell line suggested that haploinsufficiency was the mechanism of telomere shortening due to TERT mutations.

CONCLUSIONS

Heterozygous mutations in the TERT gene impair telomerase activity by haploinsufficiency and may be risk factors for marrow failure.

Tumor necrosis factor alpha polymorphism in heart failure/cardiomyopathy

Tumor necrosis factor a (TNF-alpha) is a proinflammatory cytokine that is produced by activated macrophages. It has been shown to stimulate the release of endothelial cytokines and NO, increase vascular permeability, decrease contractility, and induce a prothrombotic state. The most studied TNF-a gene mutation in heart disease is a gamma to alpha substitution, which occurs when 308 nucleotides move upstream from the transcription initiation site in the TNF promoter and has been associated with elevated levels of TNF-alpha. The TNF1 allele (wild type) contains gamma at this site, while the TNF2 allele has an alpha substitution at the site. The TNF2 allele is a more powerful transcriptional activator, therefore leading to higher TNF-alpha levels. Most of the studies to date have failed to conclusively show any link between the polymorphism and heart disease, both coronary artery disease and cardiomyopathy/heart failure.