Pathogenesis Of Autoimmune Hemolytic Anemia Research Articles

Challenges in the diagnosis and management of autoimmune hemolytic anemia: A case-based approach. Experience from a tertiary care hospital in the Haryana region.

Autoimmune hemolytic anemia (AIHA) is a rare immune disorder which occurs when antibodies are directed against self red blood cells (RBCs) leading to hemolysis. AIHA is widely classified as warm autoimmune hemolytic anemia, cold agglutinin syndrome, mixed AIHA, paroxysmal cold hemoglobinuria and rarely drug induced AIHA. The pathogenesis of AIHA is complex interplay between genetic predisposition, immune dysregulation and enviornmental triggers. A direct antiglobulin test can be used to assess the immunological origin of the hemolysis in order to diagnose AIHA after identifying laboratory and clinical symptoms of hemolysis. The objective is to understand underlying mechanism in AIHAs, and usage of targeted therapies to modulate specific components of the immune response. We are hereby presenting a case series of 11 clinically suspected cases of AIHA in collaboration with their clinical features, immuno-hematological and other laboratory parameters, Flow cytometric analysis of lymphocyte subset in relevant cases, underlying etiology as well as serological subtype are also included. Majority of the patients were categorized as secondary AIHA (7/11, 63.63%). Out of 11 cases 7 were serologically subtyped as warm AIHA (7/11, 63.63%) ,2 cases were DaaT negative AIHA (2/11;18.18%), 2 cases were characterized as mixed AIHA subtype (2/11, 18.18%). Accurate subtyping of AIHA requires a systematic immunohematological approach coupled with comprehensive evaluations of clinical, hematological, and biochemical parameters.

The Role of the Spleen and the Place of Splenectomy in Autoimmune Hemolytic Anemia-A Review of Current Knowledge.

Autoimmune hemolytic anemia (AIHA) is a rare, very heterogeneous, and sometimes life-threatening acquired hematologic disease characterized by increased red blood cell (RBC) destruction by autoantibodies (autoAbs), either with or without complement involvement. Recent studies have shown that the involvement of T- and B-cell dysregulation and an imbalance of T-helper 2 (Th2) and Th17 phenotypes play major roles in the pathogenesis of AIHA. AIHA can be primary (idiopathic) but is more often secondary, triggered by infections or drug use or as a part of other diseases. As the location of origin of autoAbs and the location of autoAb-mediated RBC clearance, as well as the location of extramedullary hematopoiesis, the spleen is crucially involved in all the steps of AIHA pathobiology. Splenectomy, which was the established second-line therapeutic option in corticosteroid-resistant AIHA patients for decades, has become less common due to increasing knowledge of immunopathogenesis and the introduction of targeted therapy. This article provides a comprehensive overview of current knowledge regarding the place of the spleen in the immunological background of AIHA and the rapidly growing spectrum of novel therapeutic approaches. Furthermore, this review emphasizes the still-existing expediency of laparoscopic splenectomy with appropriate perioperative thromboprophylaxis and the prevention of infection as a safe and reliable therapeutic option in the context of the limited availability of rituximab and other novel therapies.

Is Splenectomy still the best treatment for Autoimmune hemolytic anemia

Introduction:
 Autoimmune hemolytic anemia (AIHA) is an acquired, heterogeneous group of diseases that includes AIHA with warm type antibodies, cold agglutinin disease (CAD), mixed type AIHA, paroxysmal cold hemoglobinuria, and atypical AIHA.
 Currently CAD is defined as chronic, clonal lymphoproliferative disease, while presence of cold agglutinin in gastrointestinal tract is known as cold agglutinin syndrome. AIHA is mediated by autoantibodies against red blood cells (RBCs), these antibodies cause premature destruction of erythrocytes. The pathogenesis of AIHA is complex and still not yet fully understood.
 Aim of study:
 The purpose of the study was to review the literature on the treatment options for Autoimmune Hemolytic Anemia
 Materials and methods: A systemic review was conducted using PubMed, ScienceDirect, Google Scholar databases. The search strategy was based on following terms: Aiha, splenectomy autoimmune anemia, aiha treatment,
 Results and Conclusions:
 Based on the review of the medical literature, we believe that Splenectomy is no longer the most effective method of treating any type of AIHA and the Rituximab treatment presented by us seems to be safer and definitely less burdensome for the patient.
 Of course, splenectomy is still used in AIHA - but nowadays it is more limited due to the very high effectiveness of the described non-surgical treatment

Autoimmune hemolytic anemia: the current state of the issue

Autoimmune hemolytic anemia is a rare disease characterized by the appearance of anti-erythrocyte autoantibodies and subsequent destruction of red blood cells by cells of the immune system. The destruction mechanisms of erythrocytes loaded with autoantibodies are well studied; however, the initial mechanisms that trigger the production of antibodies to own erythrocytes antigens remain unclear. In the pathogenesis of autoimmune hemolytic anemia, an important role is played by impaired immunological tolerance, in which T-lymphocytes play a key role. The study of T-lymphocytes subpopulation in patients with autoimmune hemolytic anemia by flow cytometry can provide valuable information for studying the disease pathogenesis and developing new approaches to its treatment.

Ultrastructural analysis of nucleated erythrocyte in patients with autoimmune hemolytic anemia (AIHA)

ABSTRACT Autoimmune hemolytic anemia (AIHA) is a group of diseases characterized by immune-mediated lysis of mature red blood cells (RBCs). It is mainly classified into primary and secondary types based on etiology and mechanisms underlying autoantibody production. AIHA is diagnosed using morphological observation of bone marrow smears under a light microscope and monospecific direct antiglobulin test to detect hemolysis. Here, we retrospectively studied ultrastructural abnormalities of nucleated erythroid cells in bone marrows from 10 patients with AIHA using transmission electron microscopy. Our results revealed severe damage and injury to nucleated erythroid cells, including morphological irregularity, pyknosis, karyolysis, expansion of perinuclear cisternae and cytoplasmic lysis. These results indicate that aberrant immunity attacks not only mature RBCs but also nucleated erythroid cells, and ineffective hematopoiesis is partly involved in the pathogenesis of AIHA.

Immune Hemolytic Anemia

The diagnosis of autoimmune haemolytic anaemia (AIHA) is a challenge for both the immune-haematology laboratory and the clinician as the laboratory investigation can be troublesome and often requires extensive time-consuming serological testing, especially when a blood transfusion is needed. Frequently, there is a need to start therapy rapidly. Autoantibodies directed to epitopes on red blood cell (RBC) consisting in sugar and/or protein structures are crucial in the pathogenesis of AIHA. The isotype is important for the clinical significance of an autoantibody. Frequently, patients are icteric and suffer from clinical signs of anaemia, such as pallor, fatigue, shortness of breath and palpitations, on examination hepatosplenomegaly can be present. If there is no vital indication for a transfusion it is prudent to wait for the results of the immune-haematological tests and the ensuing transfusion advice based on this. Focus of treatment should be stoppage of hemolysis or at least be attenuated via an inhibition of autoantibody production and/or inhibition of premature RBC destruction. Successful treatment of secondary AIHA is only possible when the underlying disease is treated.

Chronic Lymphocytic Leukaemia Presenting with Pancytopenia: ARare Haematological Coincidence

Chronic Lymphocytic Leukaemia (CLL) is commonly associated with autoimmune cytopenias but CLL presenting with pancytopenia is a rare occurrence. Here, we present a case of 56-year-old male patient, who presented with pallor, mild hepatosplenomegaly, right-sided pleural effusion in chest x-ray, pancytopenia and his bone marrow showed infiltration by mature appearing lymphoid cells making a diagnosis of CLL. Despite the frequency of these immune mediated cytopenia, only few cases of pancytopenia have been described so far to the best of our knowledge. Hence, to emphasise the rarity of such haematological coincidence we are presenting this case report. CLL generally presents with persistent absolute lymphocytosis on peripheral smear with an absolute monoclonal lymphocyte count of more than 5000/cumm. There is a common association with Autoimmune Haemolytic Anaemia (AIHA) and Immune Thrombocytopenia (ITP) and the association is called as Evan’s syndrome. Its pathogenesis is associated with autoimmune process. AIHA, ITP, and Pure Red Cell Aplasia (PRCA) are commonly associated complications seen in CLL. The pathogenesis of AIHA and ITP are antibody this inplace of the reactions and abnormal T cell activity is noted in the pathogenesis of PRCA. Despite of the frequency of these immune mediated cytopenias noted in CLL, bone marrow was seen to be hypercellular in most of the cases and marrow hypoplasia have been reported in only 2 cases reported in literature so far. In the present case, although pancytopenia was present on peripheral blood smear examination but bone marrow was hypercellular for age with diffuse infiltration by monoclonal mature appearing lymphoid cells which makes this case all the more interesting. Despite repeated blood transfusions,antiviral drug Tenofovir and aggressive supportive measures for 6 months, he developed right-sided pleural effusion and succumbed to his illness.

The Role of T Follicular Helper Cells and T Follicular Regulatory Cells in the Pathogenesis of Autoimmune Hemolytic Anemia

Autoimmune hemolytic anemia (AIHA) is an acquired autoimmune disease mediated by antibodies against the patient’s red blood cells. However, the underlying mechanisms for antibody production are not fully understood. Previous studies of etiology and pathogenesis of AIHA mainly focus on autoreactive B cells that have escaped tolerance mechanisms. Few studies have reported the function of TFH and TFR cells in the process of AIHA. The present study aimed to explore the potential mechanism of TFH and TFR cells in the pathogenesis of AIHA. With the model of murine AIHA, increased ratios of TFH:TFR, elevated serum IL-21 and IL-6 levels, and upregulated Bcl-6 and c-Maf expression were reported. Also, adoptive transfer of purified CD4+CXCR5+CD25- T cells from immunized mice promoted the induction of autoantibody in the AIHA mouse model. Altogether, our data demonstrate the important role of TFH cells for control and induction of AIHA. In the light of the key contributions of TFH cells to the immune response in AIHA, strategies aimed at inhibiting the TFH development or function should be emphasized.

Research progress of mammalian target of rapamycin and occurence of autoimmune hemolytic anemia

Mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase that is involved in the immune pathogenesis of autoimmune hemolytic anemia (AIHA) by regulating different types of T cell, B cells and dendritic cells (DC). mTOR inhibitor acts on the mTOR signaling pathway. It can up-regulate the number of regulatory T cell (Treg) and down-regulate the number of helper T cell (Th), Th2, and Th17. It plays an important role in the treatment of recurrent/refractory AIHA. The authors review the molecular structure of mTOR, mTOR signaling pathway, the regulation of mTOR involved in immune cells, and the treatment of AIHA with mTOR inhibitors. Key words: TOR serine-threonine kinases; Anemia, hemolytic, autoimmune; T-lymphocytes, regulatory; Th1 cells; Molecular targeted therapy; Immunosuppressive agents

Seasonal Variation in Autoimmune Hemolytic Anemia: A National Database Analysis

Background:Autoimmune hemolytic anemia (AIHA) is a decompensated acquired hemolysis caused by host's immune system acting against its own red cell antigens. Serologically, it can be divided to warm hemolytic anemia, cold hemolytic anemia, paroxysmal cold hemoglobinuria and mixed AIHA. Pathogenesis of AIHA comprises of a series of complex interactions between genetics, environmental either conferring to protective or deteriorating effects. Among these, climatic changes appears to be key as it involves many triggers such as viral infections, temperature and other host factors. We reviewed a large national hospitalization database to determine whether rates of autoimmune hemolytic anemia have a seasonal variation over the past decade.Methods:We examined the Nationwide Inpatient Sample (NIS), a nationally representative survey of hospitalizations conducted by the Healthcare Cost and Utilization Project in collaboration with participating states. It is the largest all-payer inpatient dataset in the United States and includes a 20% sample of United States community hospitals that approximates 20% of all US community hospitals. The Nationwide Inpatient Sample (NIS) database was used to estimate annual number of hospitalizations from 2000 - 2012. Identification of autoimmune hemolytic anemia related hospitalizations was based on the designation of the prior validated International Classification of Diseases (9th Edition) Clinical Modification (ICD-9-CM) diagnosis code 283 as the principal discharge diagnosis. The frequency of hospitalization per month cumulative over 13 years was calculated and divided by number of days in that month to determine the mean hospitalizations per day for each month. All calculations were carried out using the weighted estimates approximating nationwide population estimates.Results:An estimated 48,416 hospitalizations with primary diagnosis of autoimmune hemolytic anemia occurred in the US from 2000 to 2012 as per NIS database. More specifically, the mean number of hospitalizations per day in each month is shown in Fig. 1. The mean number of hospitalizations each day was highest in November (141 per day) and thereafter the hospitalization rate dropped to a nadir in May (122 per day). There was a significant rising trend of admissions from June towards winter months with peaks in November as depicted in the Fig.1. In general, the number of hospitalization was maximum in the winter months and minimum in summer months as demonstrated in Fig.2.Conclusion:We identified for the first time in United States an impressive pattern of seasonal variation in hospitalizations for autoimmune hemolytic anemia with a notable increase in winter and fall and a significant drop during summer months. The seasonal pattern may reflect viral or other triggers for immune system activation. Further efforts need to be made to identify triggers and methods to determine the relationship of these variations and reduce this predictive burden on the overall health care system. DisclosuresNo relevant conflicts of interest to declare.

Murine models of autoimmune hemolytic anemia.

Purpose of reviewPathogenic autoantibodies directed against red blood cells (RBCs) may lead to autoimmune hemolytic anemia (AIHA), a severe and sometimes fatal disease. Much of what is known about the etiology and pathogenesis of AIHA has been learned from observations made in human patients and murine models, but many questions remain; importantly, it is still unclear why some people generate RBC-specific autoantibodies. The combination of technological advancements applied to existing models and the development of new AIHA murine models will continue to provide considerable insight into the initiation of AIHA and provide a platform for the design of more effective therapies.Recent findingsAdvancements in well described murine models of AIHA show that reticulocytes are preferentially targeted by anti-RBC autoantibodies and an increase in oxidative stress may trigger autoantibody production. Additionally, a new murine model of erythrocyte autoreactivity demonstrates that T cell tolerance is the stopgap for autoimmunity. Moreover, unlike many self-antigens, data suggest that RBC self-antigens are not presented in the thymus thereby escaping the scrutiny of T cell central tolerance mechanisms and placing emphasis on peripheral tolerance instead. Information gained from this new model provide novel insight into how the immune system responds to RBC autoantigens and provides a tractable platform to discover new therapies for AIHA.SummaryMurine models of AIHA have provided significant understanding into the risk factors for AIHA. The application of new technologies and models of erythrocyte autoreactivity is a pathway with the potential to elucidate how tolerance to RBC autoantigens is established, maintained, and broken down.

Autoimmune haemolytic anaemia and autoimmune thrombocytopenia in childhood-onset systemic lupus erythematosus: updates on pathogenesis and treatment.

Autoimmune haemolytic anaemia (AIHA) and autoimmune thrombocytopenia are common complications of childhood-onset lupus, which may be life-threatening. A greater understanding of the pathogenesis of these haematologic manifestations will enhance our understanding of the biology of systemic lupus erythematosus (SLE) and inform the identification of novel treatments. The mechanisms underlying AIHA and autoimmune thrombocytopenia are incompletely understood and likely multifactorial. Although the development of auto-antibodies is central to the disease process, recent studies have demonstrated the importance of cytokines in the underlying pathologic process. In-vitro and in-vivo evidence points to a role for IL17 in the pathogenesis of AIHA, which involves loss of tolerance to red cell auto-antigens and the development of autoantibodies. Sirolimus, an mTor inhibitor, has benefited patients with primary autoimmune cytopenias, possibly by stimulating T regulatory cells, and may also have efficacy for SLE-associated cytopenias. Similarly, low-dose recombinant human IL-2 therapy has shown promising results for improving platelet counts in patients with autoimmune thrombocytopenia, possibly by restoring the balance between T regulatory, T helper and Th17 cells. The emergence of new agents directed at restoring immune dysregulation hold promise for the treatment of AIHA and autoimmune thrombocytopenia and should provide better tolerated alternatives to high-dose corticosteroids.

Autoimunitní hemolytická anémie

Autoimmune hemolytic anemia (AIHA) is caused by auto-antibodies directed against self red blood cell (RBC) surface antigens. A consequence may be an intravascular hemolysis mediated by activated complement or extravascular hemolysis caused by destruction of complex of RBC with autoantibody in spleen and liver. The basic classification subdivides AIHA in primary/idiopathic and secondary with known underlying disease. A classification according to the thermal range of antibody recognizes warm AIHA, cold aglutinin disease (CAD), mixed AIHA and paroxysmal cold hemoglobinuria. Pathogenesis of AIHA consists of a defective antigen presentation to immunocompetent cells, insufficient process of T-lymphocyte tolerance to autoantigens and induction of autoantibody production by B-lymphocytes. For the diagnosis of AIHA are essential direct and indirect antiglobulin tests. The first-line therapy for warm AIHA is still administration of corticosteroids. For non-responding patients, second-line treatment includes rituximab or splenectomy. Combination of other immunosuppressive drugs represents a third-line treatment for resistant/relapsing patients. Rituximab is a treatment of choice for patients with CAD. Key words: anemia hemolytic - autoimmunity - corticosteroids - diagnosis - pathogenesis - rituximab - splenectomy - treatment.

The SOD1 transgene expressed in erythroid cells alleviates fatal phenotype in congenic NZB/NZW-F1 mice

Oxidative stress due to a superoxide dismutase 1 (SOD1) deficiency causes anemia and autoimmune responses, which are phenotypically similar to autoimmune hemolytic anemia (AIHA) and systemic lupus erythematosus (SLE) in C57BL/6 mice and aggravates AIHA pathogenesis in New Zealand black (NZB) mice. We report herein on an evaluation of the role of reactive oxygen species (ROS) in a model mouse with inherited SLE, that is, F1 mice of the NZB × New Zealand white (NZW) strain. The ROS levels within red blood cells (RBCs) of the F1 mice were similar to the NZW mice but lower compared to the NZB mice throughout adult period. Regarding SLE pathogenesis, we examined the effects of an SOD1 deficiency or the overexpression of human SOD1 in erythroid cells by establishing corresponding congenic F1 mice. A SOD1 deficiency caused an elevation in ROS production, methemoglobin content, and hyperoxidation of peroxiredoxin in RBC of the F1 mice, which were all consistent with elevated oxidative stress. However, while the overexpression of human SOD1 in erythroid cells extended the life span of the congenic F1 mice, the SOD1 deficiency had no effect on life span compared to wild-type F1 mice. It is generally recognized that NZW mice possess a larval defect in the immune system and that NZB mice trigger an autoimmune reaction in the F1 mice. Our results suggest that the oxidative insult originated from the NZB mouse background has a functional role in triggering an aberrant immune reaction, leading to fatal responses in F1 mice.

IL-33 reflects dynamics of disease activity in patients with autoimmune hemolytic anemia by regulating autoantibody production.

Background Autoimmune hemolytic anemia (AIHA), a life-threatening anemia with rapid onset, is caused by autoantibody directed to self red blood cells (RBCs). Currently, mechanisms underlying AIHA pathogenesis are largely undefined. Here we explored the correlation of IL-33 with AIHA disease activity and evaluated IL-33 based therapeutics in AIHA treatment.Methods Thirty patients diagnosed with AIHA of warm-type autoantibodies without treatment were enrolled and followed up for 6 months. Levels of cytokines including IL-33, IL-4, IL-6 and IL-13 was determined with ELISA. AIHA disease activity was presented by levels of reticulocyte count, hemoglobin and lactate dehydrogenase. Serum RBC-bound IgG autoantibody was detected using anti-IgG antibody with flow cytometry. To evaluate the effect of IL-33 blockade on AIHA development, groups of B6 mice were immunized with rat RBCs plus recombinant IL-33 protein or IL-33 neutralizing antibody respectively and detected for levels of anti-RBC antibody, frequency of reticulocytes and destruction of transfused syngeneic mouse RBCs.ResultsSerum level of IL-33 was higher in AIHA patients compared with healthy individuals. Of interest, serum IL-33 was positively correlated with AIHA disease activity and sensitive to their changes in AIHA patients under clinical management. Mechanistically, IL-33 could promote the production of anti-RBC autoantibody. Serum IL-33 was closely associated with serum anti-RBC autoantibody and sensitive to their changes in AIHA patients. Accordingly, blockade of IL-33 interfered with AIHA incidence and ameliorated disease activity. Vice vasa, enforced IL-33 promoted AIHA incidence and disease activity.ConclusionsIL-33 was a potential biomarker for monitoring disease activity and therapeutic response in AIHA patients. Targeting IL-33 was a promising strategy for controlling autoantibody production in AIHA patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0745-0) contains supplementary material, which is available to authorized users.

Complement inhibitors to treat IgM-mediated autoimmune hemolysis.

Complement activation in autoimmune hemolytic anemia may exacerbate extravascular hemolysis and may occasionally result in intravascular hemolysis. IgM autoantibodies as characteristically found in cold autoantibody autoimmune hemolytic anemia, in cold agglutinin disease but also in a considerable percentage of patients with warm autoantibodies are very likely to activate complement in vivo. Therapy of IgM-mediated autoimmune hemolytic anemia mainly aims to decrease autoantibody production. However, most of these treatments require time to become effective and will not stop immediate ongoing complement-mediated hemolysis nor prevent hemolysis of transfused red blood cells. Therefore pharmacological inhibition of the complement system might be a suitable approach to halt or at least attenuate ongoing hemolysis and improve the recovery of red blood cell transfusion in autoimmune hemolytic anemia. In recent years, several complement inhibitors have become available in the clinic, some of them with proven efficacy in autoimmune hemolytic anemia. In the present review, we give a short introduction on the pathogenesis of autoimmune hemolytic anemia, followed by an overview on the complement system with a special focus on its regulation. Finally, we will discuss complement inhibitors with regard to their potential efficacy to halt or attenuate hemolysis in complement-mediated autoimmune hemolytic anemia.

Molecular mechanisms of autoimmune hemolytic anemia

Autoimmune hemolytic anemia (AIHA) is an acquired immunological disease in which red blood cells (RBCs) are selectively attacked and destroyed (hemolyzed) by autoantibodies produced by the patient's own immune system. Several hypotheses regarding the mechanisms underlying the development of AIHA have been proposed, but the actual pathogenesis remains unclear. Since the major autoantigens in warm AIHA were determined to be Rh protein, band 3 and glycophorin A in 1993, helper T cells (Th1, Th2 and Th17) and regulatory T (Treg) cells specifically reacting to Rh peptides were reported in patients with AIHA. Recently, Th1 responses were found to be suppressed with synthetic peptides that are recognized by the Treg cells, and Th17 cells and interleukin 17 were shown to contribute to the induction and the development of AIHA. This approach to understanding AIHA pathogenesis may provide clues to finding novel targets for immunotherapy against AIHA.

CXCL13, CCL4, and sTNFR as circulating inflammatory cytokine markers in primary and SLE-related autoimmune hemolytic anemia.

BackgroundA considerable proportion of autoimmune hemolytic anemia (AIHA) are secondary to underlying autoimmune disorders, especially syetemic lupus erythematosus (SLE), and the clinical and laboratory index for early discrimination between primary and SLE-related AIHA has yet to be defined. In the present study, we proposed novel cytokine patterns in the pathogenesis of AIHA as well as parameters for the timely identification of SLE-related patients.MethodsAIHA patients confirmed by immunohematology techniques from September 2010 to December 2012 in our facility were consecutively included and categorized into primary (n = 19) and SLE-related (n = 18) groups. Plasma cytokine profiles were measured in a single procedure by Quantibody Human Inflammatory Array 1 (RayBiotech, Norcross, GA).ResultsSLE-related AIHA patients demonstrated younger age (39 ± 20 vs.57 ± 16 years, p = 0.004), poorer reticulocyte compensation (6.8 ± 7.1 vs.12.2 ± 8.6%, p = 0.045), lower levels of lactate dehydrogenase [361 (265-498) vs. 622 (387-1154) U/L, p = 0.004], and higher occurrence of anticardiolipin antibody [9/18 (50%) vs. 2/19 (10.9%), p = 0.009]. MCP-1/CCL2, MIP-1β/CCL4, BLC/CXCL13, IL-8/CXCL8, sTNFRI, and sTNFRII were significantly up-regulated in both groups, while sTNFRII was remarkably higher in SLE-related patients. Among both groups, hemoglobin level was negatively correlated with CXCL13 (r = -0.332, p = 0.044), while reticulocyte count was positively correlated with CCL4 (r = 0.456, p = 0.005).ConclusionCXCL13 and CCL4 could act as circulating biomarkers in AIHA, and indicated disease severity and erythroid compensation, respectively. Higher plasma sTNFRII might favor the diagnosis of SLE-related instead of primary AIHA.

Tolerance to RBC antigens; pathogenesis of autoimmune haemolytic anaemia

Autoimmune haemolytic anaemia (AIHA) ensues when humoral tolerance is lost to antigens on red blood cells (RBCs), resulting in RBC autoantibodies and haemolysis. Haemolysis can be profound, and lead to substantial morbidity, and in some cases, mortality. The pathogenesis of primary AIHA remains poorly understood. Using murine models of RBC tolerance, we have recently described that baseline tolerance to RBC antigens is complete in the CD4+ compartment. However, the T cell tolerance is not due to thymic deletion; rather, autoreactive CD4+ T cells exist in the periphery, but in an anergic and non-functional state. In contrast, B cell tolerance to RBC antigens is incomplete. Moreover, autoreactive B cells rapidly differentiate into plasma cells secreting anti-RBC autoantibodies if provided CD4+ T cell help. Together, these data indicate that the stop-gap immunological safety measure for humoral autoimmunity to RBC antigens is anergy of autoreactive CD4+ T cells, in a murine model. This model predicts that factors that reverse CD4+ T cell anergy may be instrumental in the pathogenesis of AIHA. If translatable to human biology, these findings represent a fundamental shift in understanding of AIHA pathogenesis, which has heretofore assumed that tolerance in the B cell compartment was the determining factor. Autoimmune haemolytic anaemia (AIHA) ensues when humoral tolerance is lost to antigens on red blood cells (RBCs), resulting in RBC autoantibodies and haemolysis. Haemolysis can be profound, and lead to substantial morbidity, and in some cases, mortality. The pathogenesis of primary AIHA remains poorly understood. Using murine models of RBC tolerance, we have recently described that baseline tolerance to RBC antigens is complete in the CD4+ compartment. However, the T cell tolerance is not due to thymic deletion; rather, autoreactive CD4+ T cells exist in the periphery, but in an anergic and non-functional state. In contrast, B cell tolerance to RBC antigens is incomplete. Moreover, autoreactive B cells rapidly differentiate into plasma cells secreting anti-RBC autoantibodies if provided CD4+ T cell help. Together, these data indicate that the stop-gap immunological safety measure for humoral autoimmunity to RBC antigens is anergy of autoreactive CD4+ T cells, in a murine model. This model predicts that factors that reverse CD4+ T cell anergy may be instrumental in the pathogenesis of AIHA. If translatable to human biology, these findings represent a fundamental shift in understanding of AIHA pathogenesis, which has heretofore assumed that tolerance in the B cell compartment was the determining factor.

Simultaneous detection of IgG, IgM, IgA complexes and C3d attached to erythrocytes by flow cytometry.

Immune complexes attached to erythrocyte membrane are involved in autoimmune hemolytic anemia (AIHA) pathogenesis. Currently, direct antiglobulin test (DAT) is used for AIHA diagnosis; however, its performance can be variable. The aim of this study was to design a flow cytometry protocol for simultaneous detection of IgG, IgM, IgA immune complexes and C3d attached to erythrocytes in AIHA patients . A procedure was standardized for assessing independent or simultaneous IgG, IgM, IgA immune complexes and C3d, which were detected using secondary antibodies. The protocol developed was applied to blood samples of patients with AIHA, donors at risk of developing the disease, and healthy controls. Twenty-four blood samples were assessed: nine patients with AIHA, five donors at risk of developing the disease, and 10 healthy controls. In the AIHA group, all were positive for C3d, seven for IgG, four for IgA, and one for IgM. Two AIHA patients that were negative for DAT-IgG and C3d were positive for C3d by flow cytometry. Flow cytometry is a consistent method for identifying the presence of IgG, IgM, IgA immune complexes and C3d attached to erythrocytes and can be helpful for understanding the mechanisms involved in AIHA pathogenesis.