Mechanisms of immunological tolerance loss versus erythrocyte self-antigens and autoimmune hemolytic anemia

Daratumumab monotherapy in refractory warm autoimmune hemolytic anemia and cold agglutinin disease

ABSTRACT

Autoimmune hemolytic anemia (AIHA) is a rare autoantibody-mediated disease. For steroid and/or rituximab-refractory AIHA, there is no consensus on optimal treatment. Daratumumab, a monoclonal antibody targeting CD38, could be beneficial by suppression of CD38+ plasma cells and thus autoantibody secretion. In addition, because CD38 is also expressed by activated T cells, daratumumab may also act via immunomodulatory effects. We evaluated the efficacy and safety of daratumumab monotherapy in an international retrospective study including 19 adult patients with heavily pretreated refractory AIHA. In warm AIHA (wAIHA, n = 12), overall response was 50% with a median response duration of 5.5 months (range, 2-12), including ongoing response in 2 patients after 6 and 12 months. Of 6 nonresponders, 4 had Evans syndrome. In cold AIHA (cAIHA, n = 7) overall hemoglobin (Hb) response was 57%, with ongoing response in 3 of 7 patients. One additional patient with nonanemic cAIHA was treated for severe acrocyanosis and reached a clinical acrocyanosis response as well as a Hb increase. Of 6 patients with cAIHA with acrocyanosis, 4 had improved symptoms after daratumumab treatment. In 2 patients with wAIHA treated with daratumumab, in whom we prospectively collected blood samples, we found complete CD38+ T-cell depletion after daratumumab, as well as altered T-cell subset differentiation and a severely diminished capacity for cell activation and proliferation. Reappearance of CD38+ T cells coincided with disease relapse in 1 patient. In conclusion, our data show that daratumumab therapy may be a treatment option for refractory AIHA. The observed immunomodulatory effects that may contribute to the clinical response deserve further exploration.

Autoimmune Hemolytic Anemia Associated with COVID-19 Infection in a Patient with High Cardio-metabolic Risk

The article analyses data on the occurrence of hematological abnormalities in severe acute respiratory syndrome 2 infection. Among these hematological abnormalities, the majority of patients develop a hypercoagulable state associated with thromboembolic complications and poor prognosis. Approximately one-third of patients with severe acute respiratory syndrome 2 infection are diagnosed with mild to severe thrombocytopenia. Another hematological autoimmune disease observed in patients with coronavirus disease 2019 is autoimmune hemolytic anemia. A clinical case with the development of autoimmune hemolytic anemia in the setting of coronavirus infection was described. The diagnosis was based on the presence of anemia, reticulocytosis, a significant decrease in haptoglobin levels, and a positive antiglobulin test (Coombs test). Given the comorbidity, the risks of adverse effects of severe coronavirus disease were high, despite this, it was possible to achieve clinical and hematological remission of autoimmune hemolytic anemia by prescribing pathogenetic therapy with anti-CD-20 monoclonal antibody (rituximab), recombinant erythropoietin and glucocorticoid hormones. This clinical case demonstrates the possibility of successful treatment of patients with severe hemolytic anemia. Special attention should be paid to the discrepancy between the severity of the condition and objective data. This case demonstrates the need for a more in-depth approach to each patient with anemia associated with coronavirus disease infection, namely, in the presence of anemic syndrome, it is imperative to include a full range of laboratory tests.

Hemolytic Anemia Complicating COVID-19 Infection

Coronavirus disease 2019 (COVID-19) has been associated with a spectrum of reported hematological complications ranging from immune cytopenias to thromboembolic manifestations of coagulopathy. Moreover, there have been documented cases of hemolytic anemia associated with COVID-19 infection which have been mainly attributed to development of autoantibodies. We report a case of an African-American patient who presented with hemolytic anemia in the second week after his COVID-19 diagnosis. Throughout this report, we explore the potential immune and non-immune etiologies that contributed to the patient’s hemolytic anemia in the setting of COVID-19 infection guided by a review of literature.

Aberrant microRNA expression in B lymphocytes from patients with primary warm autoimmune haemolytic anaemia

OBJECTIVE

To screen and analyze the micro-Ribonucleic Acid (miRNA) expression profile in B lymphocytes from patients with autoimmune haemolytic anaemia (AIHA) using high-throughput sequencing.

METHODS

Twelve patients with warm autoimmune haemolytic anaemia (wAIHA) and twelve healthy controls (HCs) were enrolled. CD19⁺ B lymphocytes were isolated and purified using magnetic activated cell sorting (MACS). RNA was subsequently extracted from these cells and a small RNA library was created. The miRNA expression profile was analyzed using Beijing Genomics Institute Sequencing 500 (BGISEQ-500), and stem-loop real-time quantitative PCR (stem-loop qRT-PCR) was used to verify the sequencing results. Downstream target genes of the differentially expressed miRNAs were predicted using miRanda and TargetScan online software, and GO functional enrichment and pathway enrichment analyses were performed on these genes.

RESULTS

Compared with HCs, 178 upregulated and 143 downregulated miRNAs were identified in wAIHA patients, and stem-loop qRT-PCR of four randomly selected differentially expressed miRNAs verified the sequencing results. Ninety-five significantly enriched GO terms and eighty-five significantly enriched pathways were identified. Genes targeted by differentially expressed miRNAs were found to be mainly involved in the regulation of signal transduction, metabolic processes, immune reactions, and neoplastic disease development.

CONCLUSION

The expression of miRNAs in B lymphocytes from patients with primary wAIHA was deregulated, and this phenomenon may be involved in the pathogenesis of wAIHA.

The clinical characteristics of autoimmune haemolytic anaemia/Evans syndrome patients with clonal immunoglobulin/T cell receptor gene rearrangement

OBJECTIVE

To investigate the clinical features of AIHA/ES patients with clonal Ig/TCR gene rearrangement.

METHODS

Ig/TCR gene rearrangements were measured by BIOMED-2 PCR. 44 primary AIHA/ES patients were enrolled in the study. Clinical characteristics were analyzed and compared between patients with and without clonal Ig/TCR gene rearrangement.

RESULTS

Clonal Ig/TCR rearrangements were identified in 34.09% (15/44) patients including 18.18% (8/44) clonal Ig rearrangement and 15.91% (7/44) clonal TCR rearrangement. 11.37% (5/44) patients showed TCR γ rearrangement, and 2.27% (1/44) patient showed β rearrangement. 2.27% (1/44) patient showed both γ and β chain rearrangement. The median ages of patients with Ig/TCR clonality (8 male and 7 female) and without Ig/TCR clonality (10 male and 19 female) were 60 (16 ∼ 81) and 53 (17 ∼ 78) years old, respectively. No significant differences were found in age or gender between the two groups (p = .26, p = .378). Hb and RBC of patients with Ig/TCR clonality [(64.31 ± 5.72) g/L, (1.78 ± 0.22) × 10¹²/L] were significantly lower than those of patients without Ig/TCR clonality (p = .0053 and p = .0189, respectively). The percentage of reticulocytes of Ig/TCR clonality group was obviously higher than that of patients without Ig/TCR clonality (p = .0248). No significant differences were found in levels of TBIL, IBIL, LDH, FHb, Hp, IgG, IgA, IgM, IgE, C3, C4, CD5⁺CD19⁺/CD19⁺ ratio, and CD3⁺CD4⁺/CD3⁺CD8⁺ ratio between the two groups. Treatment response of Ig/TCR clonality group occurred significantly later than that of the non-clonality group (p = .0016). There were no differences in relapse rate, time to recurrence, and duration of remission between two groups (p = .083, p = .72, and p = .61, respectively).

CONCLUSION

AIHA/ES patients with clonal Ig/TCR gene rearrangement presented more severe haemolysis and anaemia. Longer treatment is needed for these patients to obtain remission.

Fatal fulminant hemolysis-associated pulmonary embolism in mixed-type autoimmune hemolytic anemia: A case report

RATIONALE

Autoimmune hemolytic AQ5 anemia (AIHA) is an immune disorder caused by antibodies directed against unmodified autologous red blood cells. In rare cases, AIHA is comorbid with other immunological disorders; for instance, when AIHA is complicated with immunologic thrombocytopenic purpura (ITP) it is called Evans Syndrome (ES). These multiple autoimmune mechanisms are referred to as "immunological tolerance loss," which is known as a characteristic autoimmunity specific for AIHA. And there are no estimation of the risk for thromboembolism in the "immunological tolerance loss" case.

PATIENT CONCERNS

A 66-year-old man was diagnosed with ES after autologous stem cell transplantation for malignant lymphoma. His background immunological status was complicated because AIHA was mixed-type (warm and cold antibody type). The direct/indirect Coombs tests were positive. The anticomplement antibody was positive and his cold hemagglutinin level had increased. Anticardiolipin antibodies were negative: anticardiolipin β2GPI antibody ≤1.2 U/mL (<3.5), anticardiolipin immunoglobulin G antibody ≤8 U/mL (<10), and anticardiolipin immunoglobulin M antibody ≤5 U/mL (<8).

DIAGNOSES

ITP and mixed-type AIHA.

INTERVENTIONS

The patient achieved complete response by initial prednisolone therapy; however, he did not respond to corticosteroid therapy after AIHA recurrence. He required the red blood cell transfusion due to the progression of hemolytic anemia.

OUTCOMES

On the fourth day of refractory treatment following AIHA recurrence, the patient had acute respiratory failure with severe hypoxia and died. The cause of death was identified as pulmonary embolism (PE) based on the laboratory data and echocardiography findings, and a literature search suggested rapidly progressive hemolysis-induced PE.

LESSONS

Although infrequent, comorbid thromboembolism to AIHA is well documented; however, a mixed-type AIHA case complicated with thromboembolism has not been previously reported. The combined pathophysiology of AIHA and thromboembolism should be considered in the clinical course of hemolysis. Our case suggested multiple immunological background, ITP, and mixed type AIHA, could be associated to a risk for thromboembolism (TE).

Blood feast: Exploring the erythrocyte-feeding behaviour of the myxozoan Sphaerospora molnari

Aims

As the most abundant cell population in the blood, erythrocytes represent an attractive source of nutrients and a protective niche to a number of pathogens. Previously, we observed the attachment of the myxozoan parasite Sphaerospora molnari to erythrocytes of its host, common carp (Cyprinus carpio), raising a number of questions about the nature of this interaction.

Methods and results

We elucidated the impact of S molnari on the number of erythrocytes in healthy and immunocompromised fish, over a period of 6 weeks. While we observed only a mild decrease in RBC numbers in healthy individuals, we witnessed gradual and finally severe haemolytic anaemia in immunosuppressed fish. Accompanying this overt loss was increased erythropoiesis as represented by an increase of erythroblasts in the blood. In vitro, we demonstrated the uptake of host proteins from CFSE‐labelled erythrocytes, ultimately inducing death of host RBCs, likely for nutrient gain of the parasite. Nevertheless, the results do not exclude a possible role of erythrocyte‐derived proteins in immune evasion.

Conclusion

Overall, the obtained data provide first evidence for the previously unknown appetite of myxozoan parasites for host erythrocytes and create an important framework for future investigations into the molecular mechanisms underlining this interaction.

TREX1 D18N mice fail to process erythroblast DNA resulting in inflammation and dysfunctional erythropoiesis

Anaemia is commonly observed in chronic inflammatory conditions, including systemic lupus erythematosus (SLE), where ∼50% of patients display clinical signs of anaemia. Mutation at the aspartate residue 18 of the three prime repair exonuclease 1 (TREX1) gene causes a monogenic form of cutaneous lupus in humans and the genetically precise TREX1 D18N mice recapitulate a lupus-like disease. TREX1 degrades single- and double-stranded DNA (dsDNA), and the link between failed DNA degradation by nucleases, including nucleoside-diphosphate kinases (NM23H1/H2) and Deoxyribonuclease II (DNase II), and anaemia prompted our studies to investigate whether TREX1 dysfunction contributes to anaemia. Utilizing the TREX1 D18N mice we demonstrate that (1) TREX1 mutant mice develop normocytic normochromic anaemia and (2) TREX1 exonuclease participates in the degradation of DNA originating from erythroblast nuclei during definitive erythropoiesis. Gene expression, hematocrit, hemoglobin, immunohistochemistry (IHC) and flow cytometry were used to quantify dysfunctional erythropoiesis. An altered response to induced anaemia in the TREX1 D18N mice was determined through IHC, flow cytometry, and interferon-stimulated gene (ISG) expression analysis of the liver, spleen and erythroblastic islands (EBIs). IHC, flow cytometry, and ISG expression studies were performed in vitro to determine the role of TREX1 in the degradation of erythroblast DNA within EBIs. The TREX1 D18N mice exhibit altered erythropoiesis including a 20% reduction in hematocrit, 10-20 fold increased erythropoietic gene expression levels in the spleen and phenotypic signs of normocytic normochromic anaemia. Anaemia in TREX1 D18N mice is accompanied by increased erythropoietin (Epo), normal hepcidin levels and the TREX1 D18N mice display an inappropriate response to anaemic challenge. Enhanced ISG expression results from failed processing and subsequent sensing of undegraded erythroblast DNA in EBIs. TREX1 participates in the degradation of erythroblast DNA in the EBI and TREX1 D18N mice exhibit a normocytic normochromic anaemia.

Autoimmune Hemolysis: A Journey through Time

The existence of autoimmune diseases in humans has been known for almost 100 years. Currently, autoimmune pathogenesis has been attributed to more than 40 human diseases; yet it is still not clear what immune abnormalities conclusively prove underlying autoimmune pathogenesis. Hence, although much has been learned, research is still needed for complete elucidation of the mechanisms of the immune dysregulation in AIHA. Better understanding of the underlying mechanism(s) may allow for development of more specific therapies of these not uncommon and often difficult-to-treat disorders.

Oxidative stress as a potential causal factor for autoimmune hemolytic anemia and systemic lupus erythematosus

The kidneys and the blood system mutually exert influence in maintaining homeostasis in the body. Because the kidneys control erythropoiesis by producing erythropoietin and by supporting hematopoiesis, anemia is associated with kidney diseases. Anemia is the most prevalent genetic disorder, and it is caused by a deficiency of glucose 6-phosphate dehydrogenase (G6PD), for which sulfhydryl oxidation due to an insufficient supply of NADPH is a likely direct cause. Elevated reactive oxygen species (ROS) result in the sulfhydryl oxidation and hence are another potential cause for anemia. ROS are elevated in red blood cells (RBCs) under superoxide dismutase (SOD1) deficiency in C57BL/6 mice. SOD1 deficient mice exhibit characteristics similar to autoimmune hemolytic anemia (AIHA) and systemic lupus erythematosus (SLE) at the gerontic stage. An examination of AIHA-prone New Zealand Black (NZB) mice, which have normal SOD1 and G6PD genes, indicated that ROS levels in RBCs are originally high and further elevated during aging. Transgenic overexpression of human SOD1 in erythroid cells effectively suppresses ROS elevation and ameliorates AIHA symptoms such as elevated anti-RBC antibodies and premature death in NZB mice. These results support the hypothesis that names oxidative stress as a risk factor for AIHA and other autoimmune diseases such as SLE. Herein we discuss the association between oxidative stress and SLE pathogenesis based mainly on the genetic and phenotypic characteristics of NZB and New Zealand white mice and provide insight into the mechanism of SLE pathogenesis.

Reactive oxygen species exacerbate autoimmune hemolytic anemia in New Zealand Black mice

Elevated reactive oxygen species (ROS) and oxidative damage occur in the red blood cells (RBCs) of SOD1-deficient C57BL/6 mice. This leads to autoimmune responses against RBCs in aged mice that are similar to autoimmune hemolytic anemia (AIHA). We examined whether a SOD1 deficiency and/or the human SOD1 transgene (hSOD1) would affect phenotypes of AIHA-prone New Zealand Black (NZB) mice by establishing three congenic strains: those lacking SOD1, those expressing hSOD1 under a GATA-1 promoter, and those lacking mouse SOD1 but expressing hSOD1. Levels of intracellular ROS and oxidative stress markers increased, and the severity of the AIHA phenotype was aggravated by a SOD1 deficiency. In contrast, the transgenic expression of hSOD1 in an erythroid cell-specific manner averted most of the AIHA phenotype evident in the SOD1-deficient mice and also ameliorated the AIHA phenotype in the mice possessing intrinsic SOD1. These data suggest that oxidative stress in RBCs may be an underlying mechanism for autoimmune responses in NZB mice. These results were consistent with the hypothetical role of reactive oxygen species in triggering the autoimmune reaction in RBCs and may provide a novel approach to mitigating the progression of AIHA by reducing oxidative stress.

Galectin-9 ameliorates clinical severity of MRL/lpr lupus-prone mice by inducing plasma cell apoptosis independently of Tim-3

Galectin-9 ameliorates various murine autoimmune disease models by regulating T cells and macrophages, although it is not known what role it may have in B cells. The present experiment shows that galectin-9 ameliorates a variety of clinical symptoms, such as proteinuria, arthritis, and hematocrit in MRL/lpr lupus-prone mice. As previously reported, galectin-9 reduces the frequency of Th1, Th17, and activated CD8(+) T cells. Although anti-dsDNA antibody was increased in MRL/lpr lupus-prone mice, galectin-9 suppressed anti-dsDNA antibody production, at least partly, by decreasing the number of plasma cells. Galectin-9 seemed to decrease the number of plasma cells by inducing plasma cell apoptosis, and not by suppressing BAFF production. Although about 20% of CD19(-/low) CD138(+) plasma cells expressed Tim-3 in MRL/lpr lupus-prone mice, Tim-3 may not be directly involved in the galectin-9-induced apoptosis, because anti-Tim-3 blocking antibody did not block galectin-9-induced apoptosis. This is the first report of plasma cell apoptosis being induced by galectin-9. Collectively, it is likely that galectin-9 attenuates the clinical severity of MRL lupus-prone mice by regulating T cell function and inducing plasma cell apoptosis.

Preconditioning with hemin decreases Plasmodium chabaudi adami parasitemia and inhibits erythropoiesis in BALB/c mice

Increased susceptibility to bacterial and viral infections and dysfunctional erythropoiesis are characteristic of malaria and other hemolytic hemoglobinopathies. High concentrations of free heme are common in these conditions but little is known about the effect of heme on adaptive immunity and erythropoiesis. Herein, we investigated the impact of heme (hemin) administration on immune parameters and steady state erythropoiesis in BALB/c mice, and on parasitemia and anemia during Plasmodium chabaudi adami infection. Intra-peritoneal injection of hemin (5 mg/Kg body weight) over three consecutive days decreased the numbers of splenic and bone marrow macrophages, IFN-γ responses to CD3 stimulation and T(h)1 differentiation. Our results show that the numbers of erythroid progenitors decreased in the bone marrow and spleen of mice treated with hemin, which correlated with reduced numbers of circulating reticulocytes, without affecting hemoglobin concentrations. Although blunted IFN-γ responses were measured in hemin-preconditioned mice, the mice developed lower parasitemia following P.c.adami infection. Importantly, anemia was exacerbated in hemin-preconditioned mice with malaria despite the reduced parasitemia. Altogether, our data indicate that free heme has dual effects on malaria pathology.

Chronic lymphocytic leukemia-associated autoimmune hemolytic anemia

The clinical course of patients with B-cell chronic lymphocytic leukemia (CLL) is often made complicated by autoimmune phenomena which mainly target the blood cells. Among them, the autoimmune hemolytic anemia (AIHA) is the most common form. On the other hand, it is believed that CLL is the most common of the known causes of AIHA. The source of any putative autoantibody (bystander nonmalignant cells or tumor cells) is not clear yet. Recently, it has been hypothesized that leukemic B-cells may also act as professional antigen presenting cells (APCs). With respect to the management of CLL-associated AIHA, steroids still represent the first-line treatment option. Intravenous immunoglobulin, immunosuppressive drugs, and splenectomy are also frequently used for steroid-refractory forms. Furthermore, although the case series is still too small, encouraging data is now supporting the use of monoclonal antibodies, in particular anti-CD20 rituximab, in managing this often life-threatening autoimmune complication of CLL.

Deep coverage mouse red blood cell proteome: a first comparison with the human red blood cell

Mice have close genetic/physiological relationships to humans, breed rapidly, and can be genetically modified, making them the most used mammal in biomedical research. Because the red blood cell (RBC) is the sole gas transporter in vertebrates, diseases of the RBC are frequently severe; much research has therefore focused on RBC and cardiovascular disorders of mouse and humans. RBCs also host malaria parasites. Recently we presented an in-depth proteome for the human RBC. Here we present directly comparable data for the mouse RBC as membrane-only, soluble-only, and combined membrane-bound/soluble proteomes (comprising, respectively, 247, 232, and 165 proteins). All proteins were identified, validated, and categorized in terms of subcellular localization, protein family, and function, and in comparison with the human RBC, were classified as orthologs, family-related, or unique. Splice isoforms were identified, and polypeptides migrating with anomalous apparent molecular weights were grouped into putatively ubiquitinated or partially degraded complexes. Overall there was close concordance between mouse and human proteomes, confirming the unexpected RBC complexity. Several novel findings in the human proteome have been confirmed here. This comparison sheds light on several open issues in RBC biology and provides a departure point for more comprehensive understanding of RBC function.

Evidence in favor of a role of idiotypic network in autoimmune hemolytic anemia induction: theoretical and experimental studies

Formation dynamics of antibodies to rat erythrocytes (REs) and auto-antibodies to mouse erythrocytes were studied in an experimental model of autoimmune hemolytic anemia (AHA) in mice. The experimental conditions of AHA were simulated in a mathematical model of an immune network. It was found that maximal production of auto-antibodies and antibodies to REs do not synchronize. Antiserum, obtained at the peak of auto-antibodies formation, competed with REs for bounding with antibodies. This represents proof that auto-antibodies to erythrocytes and antibodies to REs are an idiotype-anti-idiotypic pair. In the autoimmune reaction, the autoreactive clone, being anti-idiotypic, responded earlier than the clone reacting to the injected antigen. Comparison of autoimmune reaction kinetics in the mathematical model of an immune network with experimental dynamics of AHA shows them to be similar. So activation of the autoreactive clone to erythrocytes during experimental AHA in mice is mediated by idiotype-anti-idiotypic interactions with the clone reacting to REs.

Autoimmune Pathogenesis and Autoimmune Hemolytic Anemia

Autoimmune hemolytic anemia (AIHA) is an autoimmune disorder in which autoantibodies are directed against an individual's own red blood cells (RBCs), leading to enhanced clearance through Fc receptor (FcR)-mediated phagocytosis. Although there is a large literature relating to clinical aspects of AIHA, relatively little work addresses how IgG autoantibodies are actually produced against RBC autoantigens. This review will first discuss the current understanding of autoimmunity in general and then focus on the knowledge of the immunopathogenic mechanisms responsible for autoantibody production in AIHA. Both human and animal studies will be discussed. Understanding theses mechanism is vital for developing antigen-specific immunotherapies to treat the disease.

Transfusion-related acute lung injury following allogeneic bone marrow transplantation in a patient with acute lymphoblastic leukemia

Transfusion-related acute lung injury (TRALI) is a clinical syndrome characterized by bilateral pulmonary edema in association with transfusions. We encountered a 23-year-old woman with acute lymphoblastic leukemia, in whom TRALI without anti-human leukocyte antigen class I and anti-granulocyte antibodies developed following allogeneic bone marrow transplantation. TRALI improved mainly in association with treatment of saline and ventilation support after several days, but graft-versus-host disease and thrombotic microangiopathy developed, resulting in death due to multiple organ failure. This case indicates that TRALI can also occur following allogeneic bone marrow transplantation.