Aplastic anemia is related to alterations in T cell receptor signaling

The ouroboros of autoimmunity

Human autoimmunity against elements conferring protective immunity can be symbolized by the 'ouroboros', a snake eating its own tail. Underlying infection is autoimmunity against three immunological targets: neutrophils, complement and cytokines. Autoantibodies against neutrophils can cause peripheral neutropenia underlying mild pyogenic bacterial infections. The pathogenic contribution of autoantibodies against molecules of the complement system is often unclear, but autoantibodies specific for C3 convertase can enhance its activity, lowering complement levels and underlying severe bacterial infections. Autoantibodies neutralizing granulocyte-macrophage colony-stimulating factor impair alveolar macrophages, thereby underlying pulmonary proteinosis and airborne infections, type I interferon viral diseases, type II interferon intra-macrophagic infections, interleukin-6 pyogenic bacterial diseases and interleukin-17A/F mucocutaneous candidiasis. Each of these five cytokine autoantibodies underlies a specific range of infectious diseases, phenocopying infections that occur in patients with the corresponding inborn errors. In this Review, we analyze this ouroboros of immunity against immunity and posit that it should be considered as a factor in patients with unexplained infection.

[The characterization analysis of pathogenic T cells in immune-mediated aplastic anemia mouse model]

Objective: This study aims, in addition to characterizing pathogenic T cells trafficking to bone marrow (BM) and other organs, to establish immune-mediated AA C.B10 mouse model by DsRed mouse (B6 background) lymph nodes (LN) cells infusion after a total body irradiation (TBI) . Methods: The C.B10 mice received a 5 Gy TBI and then were infused with DsRed mouse (B6 background) LN cells at 5×10(6)/mouse via a tail vein injection. The severity of bone marrow failure (BMF) was observed by mononuclear cell count in bone marrow and peripheral blood cell count. On days 3, 6, 9, and 12, mice were sacrificed and collected BM, spleens, LN, or thymus to analyze the dynamic change and activation status of donor T cells in these organs by a flow cytometry. At day 12, the donor-derived T cells from BM, spleens, and LN were sorted to collect the DsRed(+)CD3(+)CD4(+) T cells and DsRed(+)CD3(+)CD8(+) T cells for RNA isolation and gene expression analyses by PCR array. Results: Relative to control animals that received 5 Gy TBI without LN cell infusion, AA mice developed severe BMF with dramatic decrease in total BM cells, hemoglobin, white blood cells, and platelets in peripheral blood on days 9 and 12 after the LN cell infusion. The frequencies of DsRed(+) T cells trafficking to BM, LN, and spleens increased with time. Surprisingly, although the DsRed(+) T cells in BM increased dramatically at a level much higher than those in the spleens and LN on day 12, there were very few DsRed(+) T cells in BM on days three and six, which was significantly lower than those in spleens or LN. The frequency of DsRed(+) T cells in thymus was the lowest during the whole process. On day 12, the DsRed(+)CD3(+)CD4(+) T cells of BM, LN, and spleens from AA mice were (91.38±2.10) %, (39.78±6.98) %, and (67.87±12.77) %, respectively. On the contrary, the DsRed(+)CD3(+)CD8(+)T cells of BM, LN, and spleens were (98.21±1.49) %, (94.06±4.20) %, and (96.29±1.23) %, respectively. We assessed the donor T cell phenotypes using the CD44 and CD62L markers and found that almost all of the DsRed(+)CD4(+) or DsRed(+)CD8(+) T cells in BM were effector memory T cell phenotype from day 9 to day 12. Meanwhile, transcriptome analyses showed higher expression in CD38, IFN-γ, LAG3, CSF1, SPP1, and TNFSF13B in BM DsRed(+)CD4(+) and DsRed(+)CD8(+) T cells. However, there was a lower expression in FOXP3 and CTLA4 in BM DsRed(+)CD4(+) T cells than those in spleens and LN. Conclusions: The DsRed LN cells infusion to induce BMF in CB10 mice enabled to track the donor-derived pathogenic T cells. Besides previously published findings in this model, we demonstrated that donor CD4(+) and CD8(+) T cells primarily homed to spleens and LN, expanded and differentiated, then infiltrated in BM with a terminal effector memory phenotype. The T cells infiltrated in BM showed more activation and less immunosuppression characteristics compared to those homing to spleens and LN during the BMF development.

Plasma Metabolomic and Intestinal Microbial Analyses of Patients With Severe Aplastic Anemia

Aplastic anemia results from bone marrow failure caused by an autoimmune abnormality, but the pathogenesis of severe aplastic anemia (SAA) is not well characterized. To identify potential metabolic markers of SAA and to further elucidate the pathogenetic mechanisms of SAA, we performed a metabolomic study of plasma samples and characterized the intestinal microbiota of patients with SAA and healthy controls. Patients with SAA had more Enterobacteriales and Lactobacillales, but fewer Bacteroidales, Clostridiales, and Erysipelotrichales than healthy controls. At the species level, the abundances of Escherichia coli and others including Clostridium citroniae were higher, whereas those of Prevotella copri, Roseburia faecis, and Ruminococcus bromii were lower. Eight metabolites showed significantly different plasma concentrations in the SAA and healthy control groups. Coumaric acid, L-phenylalanine, and sulfate were present at higher concentrations in the SAA group; whereas L-glutamic γ-semialdehyde, theobromine, 3a, 7a-dihydroxy-5b-cholestane, γ-δ-dioxovaleric acid, and (12Z)-9, 10-dihydroxyoctadec-12-enoic acid were present at lower concentrations. In conclusion, patients with SAA show abnormalities in both their plasma metabolomes and intestinal microbial compositions. These differences might reflect the molecular mechanisms involved in the defective immunity that characterizes SAA.

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.

CTLA-4 and HLA-DQ are key molecules in the regulation of mDC-mediated cellular immunity by Tregs in severe aplastic anemia

Background

Regulatory T cells (Tregs) inhibit the activation of cluster of differentiation (CD) 4⁺, CD8⁺T cells and the antigen‐presenting process of antigen‐presenting cells, and may play an important role in acquired severe aplastic anemia (SAA).

Methods

Flow cytometry was used to measure CD4⁺CD25⁺CD127^dim Tregs, cytotoxic T lymphocyte antigen 4 (CTLA‐4) expression on Tregs, and human leukocyte antigen (HLA)‐DQ expression on myeloid dendritic cells (mDCs). The correlations of CTLA‐4 and HLA‐DQ with immune status and clinical indicators and the changes in these indicators after immunosuppressive therapy (IST) were analyzed.

Results

In SAA patients, the number of Tregs and their CTLA‐4 expression were low but recovered after IST; the HLA‐DQ expression on mDCs was high but decreased after IST. The CTLA‐4 expression on Tregs and the HLA‐DQ expression on mDCs showed a negative correlation. The CTLA‐4 on Tregs was positively but HLA‐DQ on mDCs negatively correlated with the number of Tregs, natural killer (NK) cell number, and CD4⁺T/CD8⁺T ratio. CTLA‐4 was positively but HLA‐DQ negatively correlated with the percentage of granulocytoid and erythroid cells in bone marrow, white blood cell count in PB, absolute neutrophil count in PB, and the percentage of reticulocytes in PB.

Conclusions

CTLA‐4/HLA‐DQ may be key in the regulation of Tregs on mDCs in SAA patients. Our findings should be helpful for further investigation of the mechanism of immune pathogenesis in SAA patients. Studies on the regulators of Treg and CTLA‐4 activity will be valuable for SAA therapeutic target research and disease monitoring.

Revisiting acquired aplastic anaemia: current concepts in diagnosis and management

Acquired aplastic anaemia is a rare, serious, immunologically mediated bone marrow failure syndrome, characterised by marrow hypoplasia of varying severity and significant pancytopenia. Careful attention and investigation, including molecular testing, is required to confirm the diagnosis and exclude other mimicking conditions, such as inherited bone marrow failure syndromes. In a proportion of patients, the disease evolves to myelodysplasia or acute myeloid leukaemia and in some there is an association with paroxysmal nocturnal haemoglobinuria. The disease has a major impact on patient quality of life. Haemopoietic stem/progenitor cell transplantation for eligible patients with an available donor is the only current curative therapy. Other patients may receive immunosuppression, most commonly with anti-thymocyte globulin and cyclosporin. An initial response to immunosuppression is often encouraging, but relapse is common. Supportive care, including management of transfusion requirements and infections, is central to management. Promising new diagnostic tools and emerging therapies will likely transform approaches to this important, chronic and life-threatening condition.

Increased CD8+CD27+perforin+ T cells and decreased CD8+CD70+ T cells may be immune biomarkers for aplastic anemia severity

OBJECTIVES

Aplastic anemia (AA) is T cell immune-mediated autoimmune disease. Aberrant T cell activation involves an imbalance in T cell homeostasis in AA. However, whether the T cell activation molecule CD27 and its ligand CD70 participate in the immune pathogenesis of AA remains ill defined.

METHODS

The frequencies of CD27/CD70 and perforin/granzyme B in different T cell subsets were detected in AA patients and healthy individuals by flow cytometry.

RESULTS

We first time demonstrate a significantly elevated proportion of CD27⁺ and significantly decreased CD70⁺ T cells from AA. Changed frequency of CD27⁺ and CD70⁺ in different T cell subsets appeared to be associated with AA severity. In very severe aplastic anemia (VSAA) and severe aplastic anemia (SAA), increased CD8⁺CD27⁺ T cells present with a cytotoxic effector phenotype by elevating perforin proportion.

CONCLUSIONS

Elevated proportion of CD27 in T cells may contribute to distinct immune pathogenesis for different severities of AA. The CD8⁺CD27⁺perforin⁺ T cells combined with CD8⁺CD70⁺ T cells may serve as an immune biomarker for AA severity estimation.

The Progress of Traditional Chinese Medicine in the Treatment of Aplastic Anemia

Aplastic anemia (AA) is a common hematologic disease that is characterized by hematopoietic failure of the bone marrow and pancytopenia of the peripheral blood, which can be divided into severe and non-severe aplastic ane-mia, or acute and chronic aplastic anemia according to the severity of the disease and the progress of the clinical course. During the past years, the advantages of Traditional Chinese Medicine (TCM) on the treatment of AA have been well clarified and its theory system has been improved as well. This review is mainly on representing the pathogenesis, therapeutic principle and method, research progression, and advantages of TCM on AA.

Aplastic anemia secondary to nivolumab and ipilimumab in a patient with metastatic melanoma: a case report

Background

Immune checkpoint blockade (ICB) is becoming an increasingly prevalent strategy in the clinical realm of cancer therapeutics. With more patients being administered ICB for a host of tumor types, the scope of adverse events associated with these drugs will likely grow. Here we report a case of aplastic anemia (AA) in a patient with metastatic melanoma secondary to dual ICB therapy. To our knowledge, this is only the second case of AA secondary to dual ICB in the literature, and the first to have a positive patient outcome.

Case presentation

A 51-year old male with metastatic melanoma was started on dual immune checkpoint blockade, in the form ipilimumab (3 mg/kg) and nivolumab (1 mg/kg). Two weeks following the second cycle, he presented to the emergency department with profound polypipsia, polyuria and fatigue. The patient was diagnosed with diabetic ketoacidosis secondary to immune therapy induced type-1 diabetes and was admitted to the ICU. While in hospital the patient developed a symptomatic anemia and neutropenia. A bone marrow biopsy revealed a markedly hypocellular marrow with trinlineage hypoplasia with no evidence of myelodysplasia, neoplasm or excess blasts. Flow cytometry revealed an inverted CD4⁺:CD8⁺ ratio and an absence of hematogones. Taken together the presumed etiology was AA secondary to immunotherapy. The patient was subsequently started in IV methylprednisone 70 mg/day for 8 days, followed by a prednisone taper. This intervention rectified the bicytopenia and to date the patient has shown stable blood counts.

Conclusion

With the use of ICBs becoming increasingly prevalent in the clinical arena, the number of patients presenting with immune-related adverse events will likely increase. The current case illustrates the need to be vigilant when managing cancer patients receiving ICB. The resolution of this patient’s AA with corticosteroids highlights the value of early detection and appropriate treatment of these rare immune-mediated adverse events.