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

Upregulation of NKG2D ligands impairs hematopoietic stem cell function in Fanconi anemia

Fanconi anemia (FA) is the most prevalent inherited bone marrow failure (BMF) syndrome. Nevertheless, the pathophysiological mechanisms of BMF in FA have not been fully elucidated. Since FA cells are defective in DNA repair, we hypothesized that FA hematopoietic stem and progenitor cells (HSPCs) might express DNA damage–associated stress molecules such as natural killer group 2 member D ligands (NKG2D-Ls). These ligands could then interact with the activating NKG2D receptor expressed in cytotoxic NK or CD8⁺ T cells, which may result in progressive HSPC depletion. Our results indeed demonstrated upregulated levels of NKG2D-Ls in cultured FA fibroblasts and T cells, and these levels were further exacerbated by mitomycin C or formaldehyde. Notably, a high proportion of BM CD34⁺ HSPCs from patients with FA also expressed increased levels of NKG2D-Ls, which correlated inversely with the percentage of CD34⁺ cells in BM. Remarkably, the reduced clonogenic potential characteristic of FA HSPCs was improved by blocking NKG2D–NKG2D-L interactions. Moreover, the in vivo blockage of these interactions in a BMF FA mouse model ameliorated the anemia in these animals. Our study demonstrates the involvement of NKG2D–NKG2D-L interactions in FA HSPC functionality, suggesting an unexpected role of the immune system in the progressive BMF that is characteristic of FA.

Prognostic value of TNF-a-308 and IFN-g-874 single nucleotide polymorphisms and their plasma levels in patients with aplastic anemia

Background

Aplastic anemia (AA), an unusual hematological disease, is characterized by hypoplasia of the bone marrow and failure to form blood cells of all three lineages resulting in pancytopenia. This study aimed to investigate TNF-α-308 and IFN-γ-874 gene polymorphisms and their respective plasma protein levels in patients with AA and healthy controls.

Methods

Two hundred and forty individuals were included in this study; the case group comprised 120 AA patients, while 120 healthy individuals served as controls. Genotyping was performed using the PCR-restriction length fragment polymorphism method and TNF-α-308 and IFN-γ-874 plasma levels were evaluated using an ELISA kit.

Results

There was a significantly higher prevalence of the IFN-γ-874 genotype in patients with AA than in healthy controls, while the TNF-α-308 genotype was associated with lower risk of developing AA. Furthermore, the levels of both TNF-α-308 and IFN-γ-874 were higher in the plasma of AA patients.

Conclusion

Our findings suggest that the IFN-γ-874 genotype may be a greater risk factor in the causation of AA, whereas the TNF-α-308 genotype has a protective role in the North Indian population.

Incidence of Severe Chronic Neutropenia in South Korea and Related Clinical Manifestations: A National Health Insurance Database Study

Background and objectives: Severe chronic neutropenia (SCN) is a condition in which absolute neutrophil counts remain at a low level (under 500/µL) over months or years. Because of the rare onset of SCN, its epidemiology, prognosis, and clinical manifestations have not yet been fully understood. In particular, large-cohort studies in Asian countries are still insufficient. Therefore, in this study, national health insurance data was used to investigate the epidemiologic features and prognosis of SCN in South Korea. Materials and Methods: The data from the Health Insurance Review and Assessment database recorded between 1 January 2011 and 31 December 2015 were explored. SCN was defined based on the ICD-10 code, registry of benefit extension policy, and inclusion criteria of the study. After identifying patients with SCN, annual incidence and their co-morbidities were analyzed. Results: Among the initially identified patients with severe neutropenia (N = 2145), a total of 367 patients had SCN and were enrolled. The annual incidence rate of SCN ranged from 0.12 to 0.17 per 100,000 person-year (PY) during the study period. The highest incidence was observed in pediatric patients aged between 0 to 9 years (N = 156), followed by women in their fifties (N = 43). The total incidence rate was 0.17 in females and 0.12 in males (Relative risk (RR): 1.43, 95%, CI: 1.16–1.76). The most common accompanying condition was mild respiratory infection, but about 3.2% of patients progressed to hematologic malignancy after an average of 2.4 years. Conclusions: This nationwide population-based epidemiological study showed that incidence of SCN is higher in pediatrics and middle-aged women. As progression to hematologic malignancy was significantly higher in the age of in 45–49 years old, careful follow-up is necessary in this group. However, since this study lacks the molecular information, these finding need to be interpreted with great caution.

Somatic HLA Mutations Expose the Role of Class I-Mediated Autoimmunity in Aplastic Anemia and its Clonal Complications

Acquired aplastic anemia (aAA) is an acquired deficiency of early hematopoietic cells, characterized by inadequate blood production, and a predisposition to myelodysplastic syndrome (MDS) and leukemia. Although its exact pathogenesis is unknown, aAA is thought to be driven by Human Leukocyte Antigen (HLA)-restricted T cell immunity, with earlier studies favoring HLA class II-mediated pathways. Using whole exome sequencing (WES), we recently identified two aAA patients with somatic mutations in HLA class I genes. We hypothesized that HLA class I mutations are pathognomonic for autoimmunity in aAA, but were previously underappreciated because the Major Histocompatibility Complex (MHC) region is notoriously difficult to analyze by WES. Using a combination of targeted deep sequencing of HLA class I genes and single nucleotide polymorphism array (SNP-A) genotyping we screened 66 aAA patients for somatic HLA class I loss. We found somatic HLA loss in eleven patients (17%), with thirteen loss-of-function mutations in HLA-A*33:03, HLA-A*68:01, HLA-B*14:02 and HLA-B*40:02 alleles. Three patients had more than one mutation targeting the same HLA allele. Interestingly, HLA-B*14:02 and HLA-B*40:02 were significantly overrepresented in aAA patients, compared to ethnicity-matched controls. Patients who inherited the targeted HLA alleles, regardless of HLA mutation status, had a more severe disease course with more frequent clonal complications as assessed by WES, SNP-A, and metaphase cytogenetics, and more frequent secondary MDS. The finding of recurrent HLA class I mutations provides compelling evidence for a predominant HLA class I-driven autoimmunity in aAA, and establishes a novel link between aAA patients' immunogenetics and clonal evolution.

Minor populations of paroxysmal nocturnal hemoglobinuria-type cells in patients with chronic idiopathic neutropenia

Chronic idiopathic neutropenia (CIN) is an acquired disorder of granulopoiesis characterized by increased apoptosis of the bone marrow (BM) granulocytic progenitor cells under the influence of pro-inflammatory mediators and oligoclonal/monoclonal T-lymphocytes. Because patients with immune-mediated BM failure display frequently paroxysmal nocturnal hemoglobinuria (PNH)-type cells in the peripheral blood (PB), we investigated the possible existence of PNH-type cells in 91 patients with CIN using flow cytometry. The patients displayed increased proportions of PNH-type glycophorin A⁺ /CD59^dim and glycophorin A⁺ /CD59^- red blood cells (RBCs), FLAER^- /CD24^- granulocytes, and FLAER^- /CD14^- monocytes, compared to controls (n = 55). A positive correlation was found between the proportions of PNH-type RBCs, granulocytes, and monocytes and an inverse correlation between the number of PB neutrophils and the proportions of PNH-type cell populations. The number of patients, displaying percentages of PNH-type cells above the highest percentage observed in the control group, was significantly increased among patients with skewed compared to those with normal T-cell receptor repertoire suggesting that T-cell-mediated immune processes underlie the emergence of PNH-type cells in CIN. Our findings suggest that patients with CIN display PNH-type cells in the PB at a high frequency corroborating the hypothesis that CIN belongs to the immune-mediated BM failure syndromes.

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.