The immune haemolytic anaemias: a century of exciting progress in understanding

Increasing Incidence and Prevalence of Acquired Hemolytic Anemias in Denmark, 1980-2016

Background

Acquired hemolytic disorders—autoimmune hemolytic anemia (AIHA), cold agglutinin disease (CAD), paroxysmal nocturnal hemoglobinuria (PNH), drug-induced hemolysis (DIHA), and acquired hemolysis not otherwise specified (AHNOS)—are considered rare. Despite their potentially major health implications, data regarding their incidence and prevalence are scarce.

Methods

To fill this gap we collected data regarding all patients with acquired hemolytic disorder diagnoses in 1977–2016 from the Danish National Patient Register. These data were linked with vital and migration status information from the Danish Civil Registration System. From these data combined with annual demographic data for the background population, we calculated age- and sex-specific incidence rates and prevalence proportions of acquired hemolytic disorders for specified time periods.

Results

Our analysis included 5868 patients with acquired hemolytic disorders (2715 with AIHA, 112 CAD, 397 DIHA, 116 PNH, and 2154 AHNOS). The incidence rates per 100 000 person-years in 1980–1993 and 2008–2016 were 0.81 and 1.77 for AIHA, 0.31 and 0.12 for DIHA, and 0.04 and 0.08 for PNH, respectively. The 2008–2016 CAD incidence rate was 0.18/100 000 person-years, CAD diagnosis code was not defined before 1994. All incidence rates increased with age. The prevalence proportion per 100 000 persons in 1980 and 2015 was 2.52 and 17.01 for AIHA, 0.80 and 1.50 for DIHA, and 0.18 and 1.04 for PNH. CAD prevalence in 2015 was 1.04/100 000 persons.

Conclusion

Acquired hemolytic anemia incidence rates and prevalence proportions with the exception of DIHA are markedly increasing.

Anemias raras y fallos medulares hereditarios

Las anemias raras y los fallos medulares hereditarios son enfermedades hematológicas caracterizadas, respectivamente, por una disminución de la concentración de hemoglobina o por diversos grados de defectos en la producción de células hematopoyéticas que conducen desde una citopenia de un solo linaje hasta una de múltiples linajes. Son enfermedades raras y difíciles de diagnosticar debido a la heterogeneidad clínica, citológica y genética. En este artículo abordaremos en primer lugar el diagnóstico de las anemias raras y sus causas principales: fallos medulares, defectos del hematíe y trastornos del metabolismo de los factores de maduración eritrocitario. Seguidamente introduciremos los fallos medulares hereditarios y su patología asociada, como son las malformaciones congénitas y la predisposición tumoral, haciendo especial hincapié en los más frecuentes: la anemia de Fanconi, la disqueratosis congénitca, la anemia de Diamond-Blackfan y el síndrome de Shwachman-Diamond.

Autoimmune hemolytic anemia caused by anti "e": A challenge: A case report with review of literature

Autoimmune hemolytic anemia (AIHA) is featured by short red cell survival due to autoantibodies. AIHA caused by anti 'e' is a tough clinical situation as antigen 'e' is a highly prevalent antigen. The present case highlights the same and different issues related to it.

Identification of Stages of Erythroid Differentiation in Bone Marrow and Erythrocyte Subpopulations in Blood Circulation that Are Preferentially Lost in Autoimmune Hemolytic Anemia in Mouse

Repeated weekly injections of rat erythrocytes produced autoimmune hemolytic anemia (AIHA) in C57BL/6 mice after 5–6 weeks. Using the double in vivo biotinylation (DIB) technique, recently developed in our laboratory, turnover of erythrocyte cohorts of different age groups during AIHA was monitored. Results indicate a significant decline in the proportion of reticulocytes, young and intermediate age groups of erythrocytes, but a significant increase in the proportion of old erythrocytes in blood circulation. Binding of the autoantibody was relatively higher to the young erythrocytes and higher levels of intracellular reactive oxygen species (ROS) were also seen in these cells. Erythropoietic activity in the bone marrows and the spleen of AIHA induced mice was examined by monitoring the relative proportion of erythroid cells at various stages of differentiation in these organs. Cells at different stages of differentiation were enumerated flow cytometrically by double staining with anti-Ter119 and anti-transferrin receptor (CD71) monoclonal antibodies. Erythroid cells in bone marrow declined significantly in AIHA induced mice, erythroblast C being most affected (50% decline). Erythroblast C also recorded high intracellular ROS level along with increased levels of membrane-bound autoantibody. No such decline was observed in spleen. A model of AIHA has been proposed indicating that binding of autoantibodies may not be a sufficient condition for destruction of erythroid cells in bone marrow and in blood circulation. Last stage of erythropoietic differentiation in bone marrow and early stages of erythrocytes in blood circulation are specifically susceptible to removal in AIHA.

Evidence Suggesting Complement Activation and Haemolysis at Core Temperature in Patients with Cold Autoimmune Haemolytic Anaemia

BACKGROUND

It is unclear why haemolysis may somewhat persist in patients with cold autoimmune haemolytic anaemia (cAIHA) at 37 °C (core temperature).

METHODS

Seven patients with cAIHA were included in this study. Serological testing was performed using standard techniques. Bound autoantibodies (aab) on patients' RBCs were analysed by the direct antiglobulin test (DAT), dual antiglobulin test (DDAT) and flow cytometry (FC) using pre-warmed RBCs (37 °C). Temperature-dependent complement binding was determined by incubation of patients' serum samples with group O RBCs and fresh serum complement.

RESULTS

The DAT was strongly positive with anti-C3d in all cases, independent of season and outside temperature. Haemolysis usually improved during warm periods of time, but decompensated following febrile infections, and persisted throughout the year, though exposure to the cold was strictly avoided. In addition, trace amounts of IgM aab were infrequently detectable on patients' RBCs even at 37 °C, and complement activation was demonstrated following incubation of RBCs with the causative aab at 37 °C.

CONCLUSIONS

Binding of trace amounts of IgM aab at 37 °C may provide an explanation for the durable C3d-positive DAT and haemolysis in patients with cAIHA.

Diagnostic and therapeutic considerations in idiopathic hypereosinophilia with warm autoimmune hemolytic anemia

Hypereosinophilic syndrome (HES) encompasses numerous diverse conditions resulting in peripheral hypereosinophilia that cannot be explained by hypersensitivity, infection, or atopy and that is not associated with known systemic diseases with specific organ involvement. HES is often attributed to neoplastic or reactive causes, such as chronic eosinophilic leukemia, although a majority of cases remains unexplained and are considered idiopathic. Here, we review the current diagnosis and management of HES and present a unique case of profound hypereosinophilia associated with warm autoimmune hemolytic anemia requiring intensive management. This case clearly illustrates the limitations of current knowledge with respect to hypereosinophilia syndrome as well as the challenges associated with its classification and management.

Emergence of long-lived autoreactive plasma cells in the spleen of primary warm auto-immune hemolytic anemia patients treated with rituximab

Primary warm autoimmune hemolytic anemia (wAIHA) is a rare autoimmune disease in which red blood cells are eliminated by IgG autoantibodies. We analyzed the antibody-secreting cells in the spleen and the peripheral blood of wAIHA patients in various contexts of treatment. Plasmablasts were observed in peripheral blood of newly diagnosed wAIHA patients and, accordingly, active germinal center reactions were present in the spleen of patients receiving short-term corticosteroid therapy. Long-term corticosteroid regimens markedly reduced this response while splenic plasma cells were able to persist, a fraction of them secreting anti-red blood cell IgG in vitro. In wAIHA patients treated by rituximab and who underwent splenectomy because of treatment failure, plasma cells were still present in the spleen, some of them being autoreactive. By using a set of diagnostic genes that allowed us to assess the plasma cell maturation stage, we observed that these cells displayed a long-lived program, differing from the one of plasma cells from healthy donors or from wAIHA patients with various immunosuppressant treatments, and more similar to the one of normal long-lived bone-marrow plasma cells. Interestingly, an increased level of B-cell activating factor (BAFF) was observed in the supernatant of spleen cell cultures from such rituximab-treated wAIHA patients. These results suggest, in line with our previous report on primary immune thrombocytopenia, that the B-cell depletion induced by rituximab promoted a suitable environment for the maturation and survival of auto-immune long-lived plasma cells in the spleen.

Autoimmune hemolytic anemia: From lab to bedside

Autoimmune hemolytic anemia (AIHA) is not an uncommon clinical disorder and requires advanced, efficient immunohematological and transfusion support. Many AIHA patients have underlying disorder and therefore, it is incumbent upon the clinician to investigate these patients in detail, as the underlying condition can be of a serious nature such as lymphoproliferative disorder or connective tissue disorder. Despite advances in transfusion medicine, simple immunohematological test such as direct antiglobulin test (DAT) still remains the diagnostic hallmark of AIHA. The sensitive gel technology has enabled the immunohematologist not only to diagnose serologically such patients, but also to characterize red cell bound autoantibodies with regard to their class, subclass and titer in a rapid and simplified way. Detailed characterization of autoantibodies is important, as there is a relationship between in vivo hemolysis and strength of DAT; red cell bound multiple immunoglobulins, immunoglobulin G subclass and titer. Transfusing AIHA patient is a challenge to the immunohematologist as it is encountered with difficulties in ABO grouping and cross matching requiring specialized serological tests such as alloadsorption or autoadsorption. At times, it may be almost impossible to find a fully matched unit to transfuse these patients. However, transfusion should not be withheld in a critically ill patient even in the absence of compatible blood. The “best match” or “least incompatible units” can be transfused to such patients under close supervision without any serious side-effects. All blood banks should have the facilities to perform the necessary investigations required to issue “best match” packed red blood cells in AIHA. Specialized techniques such as elution and adsorption, which at times are helpful in enhancing blood safety in AIHA should be established in all transfusion services.

Primary cold agglutinin-associated lymphoproliferative disease: a B-cell lymphoma of the bone marrow distinct from lymphoplasmacytic lymphoma

Primary chronic cold agglutinin disease is a rare hemolytic disease mediated by monoclonal IGHV4-34-encoded cold agglutinins with a predominant specificity for the blood group antigen I. Bone marrow from 54 patients was studied to type the underlying lymphoproliferative disorder better. Bone marrow biopsies showed circumscribed intra-parenchymatous nodules with small monotonous monoclonal B cells in 40/54 patients (median infiltration: 10% of marrow cells) with a CD20(+), IgMs(+), IgDs(+), CD27(+), CD5(-/+), CD11c(-), CD23(-), CD38(-) immunophenotype. Neither plasmacytoid cytological features nor expression of plasma cell differentiation-associated transcription factors MUM1, XBP1 and BLIMP1 were noted in these B cells. However, a limited number of mature monoclonal IgM(+), IgD(-) plasma cells were present outside the lymphoid nodules and were diffusely scattered throughout the marrow. Of interest, the MYD88 L265P mutation, typical of lymphoplasmacytic lymphoma, was not detected (17/17 cases). Somatically mutated monoclonal IGHV4-34 gene rearrangement was demonstrated in eight patients with frozen samples (mean sequence homology 95.4%). However, mutations of BCL6 intron 1 were not demonstrated, except in one patient, suggesting that the lymphoma cells had not matured in the germinal center. In conclusion, cold agglutinin-associated lymphoproliferative disease displays homogeneous histological and immunophenotypic features. The absence of plasmacytoid cells, the presence of plasma cells predominantly outside the nodular lymphoid infiltrates, IGHV4-34 restriction and absence of MYD88 L265P mutation strongly suggest that cold agglutinin-associated lymphoproliferative disease is a distinct entity that is different from lymphoplasmacytic lymphoma.

Immunotherapy treatments of warm autoimmune hemolytic anemia

Warm autoimmune hemolytic anemia (WAIHA) is one of four clinical types of autoimmune hemolytic anemia (AIHA), with the characteristics of autoantibodies maximally active at body temperature. It produces a variable anemia—sometimes mild and sometimes severe. With respect to the absence or presence of an underlying condition, WAIHA is either idiopathic (primary) or secondary, which determines the treatment strategies in practice. Conventional treatments include immune suppression with corticosteroids and, in some cases, splenectomy. In recent years, the number of clinical studies with monoclonal antibodies and immunosuppressants in the treatment of WAIHA increased as the knowledge of autoimmunity mechanisms extended. This thread of developing new tools of treating WAIHA is well exemplified with the success in using anti-CD20 monoclonal antibody, Rituximab. Following this success, other treatment methods based on the immune mechanisms of WAIHA have emerged. We reviewed these newly developed immunotherapy treatments here in order to provide the clinicians with more options in selecting the best therapy for patients with WAIHA, hoping to stimulate researchers to find more novel immunotherapy strategies.

How I treat autoimmune hemolytic anemias in adults

Autoimmune hemolytic anemia is a heterogeneous disease with respect to the type of the antibody involved and the absence or presence of an underlying condition. Treatment decisions should be based on careful diagnostic evaluation. Primary warm antibody autoimmune hemolytic anemias respond well to steroids, but most patients remain steroid-dependent, and many require second-line treatment. Currently, splenectomy can be regarded as the most effective and best-evaluated second-line therapy, but there are still only limited data on long-term efficacy and adverse effects. The monoclonal anti-CD20 antibody rituximab is another second-line therapy with documented short-term efficacy, but there is limited information on long-term efficacy and side effects. The efficacy of immunosuppressants is poorly evaluated. Primary cold antibody autoimmune hemolytic anemias respond well to rituximab but are resistant to steroids and splenectomy. The most common causes of secondary autoimmune hemolytic anemias are malignancies, immune diseases, or drugs. They may be treated in a way similar to primary autoimmune hemolytic anemias, by immunosuppressants or by treatment of the underlying disease.

New treatment options for immune-mediated hematological disorders

In recent years, there has been a tremendous increase in the number of clinical studies with monoclonal antibodies and small molecules in the treatment of hematological malignancies. Clinical observations have shown that some of these molecules may also aid in the treatment of immune-mediated hematological disorders. Moreover, immunotherapy has become an important treatment cornerstone in other, non-hematological, auto-immune diseases. This paper reviews the current state of the use of these new molecules in the treatment of the most frequently encountered immune-mediated hematological disorders: auto-immune hemolytic anemia (AIHA), idiopathic thrombocytopenic purpura (ITP), and thrombotic thrombocytopenic purpura (TTP).

Autoimmune hemolytic anemia and common variable immunodeficiency: a case-control study of 18 patients

To describe the main characteristics and treatment of autoimmune hemolytic anemia (AHA) in patients with common variable immunodeficiency (CVID), we analyzed data from 18 patients, 4 from an earlier study and 14 from the French DEF-I cohort on adult patients with primary hypogammaglobulinemia. To be included, patients had to have CVID and a previous history of AHA with a hemoglobin level < or =90 g/L at onset. To determine whether AHA is associated with a particular clinical phenotype of CVID, we conducted a case-control study from the DEF-I cohort. The estimated frequency of AHA in CVID patients from the DEF-I cohort was 5.5% (14/252). Median age at AHA diagnosis was 26 years (range, 1-57 yr), and 27.5 years (range, 5-61 yr) at CVID diagnosis. CVID was diagnosed before the onset of AHA in only 2 patients (11%). CVID was diagnosed more than 6 months after AHA in 10 cases (55.5%), and the 2 conditions were diagnosed concomitantly in 6 cases. The 14 patients included in the DEF-I cohort were compared with 238 control patients with CVID but without AHA. Corticosteroids were used as initial treatment for all patients in the current study. An initial response was obtained in 15 of 18 (83%) patients. Overall, 9 of these (60%) achieved a lasting response with steroids alone (7 patients) or in combination with intravenous immunoglobulin (2 patients). Seven patients underwent splenectomy, and 5 additional splenectomies were performed for associated autoimmune thrombocytopenic purpura. After splenectomy, a lasting response was obtained in 3 of the 7 patients with AHA. However, 5 of the 12 splenectomized patients experienced life-threatening infection. Severe infection occurred in 2 of 4 patients receiving immunosuppressive drugs. At the end of follow-up, 13 of 18 (72%) patients were in treatment-free remission (13 complete responses), and 4 of 18 (22%) were in remission while on prednisone < or =20 mg/d. One patient had died, of cancer.

Autoimmune hemolytic anemia in children

The clinical and hematological profile and treatment outcome of children with warm autoimmune hemolytic anemia (AIHA) were assessed using retrospective case record analysis. There were 26 (17 idiopathic; 9 secondary) patients with a median age of 11 years. Pallor (100%), fever (39%), and jaundice (59%) were the main presenting complaints. Jaundice was much more common in idiopathic (70%) compared to secondary (44%). Direct antiglobulin test was negative in 3 patients. Oral prednisolone produced remission in 81% patients. Four patients relapsed after a median period of 7 months (2 months to 2 year) after response. All responded to a second course of steroids in median 14 days. One child required cyclosporin A in addition. No correlation was found between response and parameters such as age, sex, jaundice, low pretreatment hemoglobin, reticulocyte count, total leukocyte count, platelet count, subtype of AIHA, and hepatosplenomegaly. Relapse correlated with increased duration between the onset of symptoms and treatment. This study indicates that oral prednisolone is an effective therapy for autoimmune hemolytic anemia. In refractory cases cyclosporine A may be useful.

Autoimmune hemolytic anemia in India: clinico-hematological spectrum of 79 cases

The clinico-hematological profile and treatment outcome of patients with autoimmune hemolytic anemia (AIHA) were assessed using a retrospective case record analysis. There were 79 (52 primary; 27 secondary) consecutive patients identified with a median age of 30.5 years. The main presenting complaints were pallor (94%), fever (46%), jaundice (51%), bleeding manifestations (10%) and splenomegaly (68%). Jaundice was much more common in primary (63%) as opposed to secondary (26%) disease. The direct antiglobulin test was negative in six patients. Oral prednisolone produced remission in 87.5% patients. Six patients (three children, three adults) relapsed after a median period of 2 months after response. All of these responded to a second course of steroids, in a median period of 14 days. No correlation was found between response and the parameters of age, sex, jaundice, low pretreatment hemoglobin, reticulocyte count, total leucocyte count (TLC), platelet count, subtype of AIHA and hepatosplenomegaly. Relapse correlated with increased duration between the onset of symptoms and treatment (r = 0.996; p = 0.0001).

Treatment of isolated severe immune hemolytic anaemia associated with systemic lupus erythematosus: 26 cases

The aim of this study was to evaluate the response to treatment and the long-term outcome in a cohort of patients in whom severe autoimmune hemolytic anaemia (AHA) was the leading manifestation of systemic lupus erythematosus (SLE). Twenty-six women with severe isolated AHA were included. Corticosteroids were used as the initial treatment for all patients in our study. An initial response was obtained in all but one patient (96%). The overall recurrence rate was three per 100 person-years, with an expected recurrence-free proportion of 73% with a 180 months median follow-up. Seven patients (27%) experienced a relapse of AHA. We found a higher proportion of pleuritis in relapsing patients. Only three patients experienced multiple relapses despite splenectomy and several immunosuppressants. Steroid-sparing effect of hydroxychloroquine and azathioprine could not be assessed because most of the patients received these treatments for other reasons than AHA. Intravenous immunoglobulins induced transient response in three cases. Splenectomy was efficient to definitively control AHA in one patient but two patients quickly experienced relapses while one patient did not benefit. Five patients received immunosuppressants that induced only transient responses. Rituximab was long-term efficient in one case. In conclusion, severe AHA is a serious complication of SLE that warrants appropriate management. On the basis of our experience, the ideal treatment of isolated AHA should be oral corticosteroids in first-line treatment. Our study does not support an important role for splenectomy. Patients refractory to conventional therapy should be treated either with few toxic immunosuppressive drugs, danazol or rituximab.

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.

Two cases of refractory warm autoimmune hemolytic anemia treated with rituximab

Autoimmune hemolytic anemia is thought to be mediated via auto-antibodies produced by lymphoid B cells. This may be an idiopathic process or secondary to an underlying infection or lymphoproliferative disorder. Conventional treatment comprises immunosuppression with corticosteroids and, in some cases, splenectomy. A proportion of patients require lifelong immunosuppression to maintain disease remission. Monoclonal antibody rituximab has gained widespread acceptance in the management of B-cell malignancies. Additionally, it has been used to treat disorders associated with auto-antibody production, such as cold hemagglutinin disease, immune thrombocytopenia, and Evans syndrome. Its use in the treatment of patients with autoimmune hemolytic anemia in the setting of allogeneic bone marrow transplantation as well as in patients with an underlying lymphoproliferative disease has also been reported. We report herein the successful use of rituximab in the treatment of two patients with idiopathic refractory warm autoimmune hemolytic anemia, who are still in remission at 15 and 9 months following treatment.

A red blood cell autoantibody with mimicking anti-E specificity

BACKGROUND

Uncommonly, antibodies that appear to exhibit antigenic specificity on red blood cell (RBC) panels fail to maintain specificity following alloadsorption (i.e., they mimic antigenic specificity). Understanding both the pitfalls and the proper pathways to establish the diagnosis and to interpret the clinical significance of these mimicking antibodies is important for patient management.

CASE REPORT

A 68-year-old woman was admitted with dyspnea, anemia, bilateral pulmonary emboli, and metastatic ovarian cancer. Blood bank evaluation identified anti-E reactivity in the patient's plasma sample and a positive direct antiglobulin test (DAT).

RESULTS

The DAT was positive for immunoglobulin G and negative for C3b. An eluate of the RBCs showed E-antigen specificity on a RBC antibody panel. Repeat serologic testing with RBC antibody panels with adsorbed patient plasma showed removal of apparent anti-E reactivity with either E-antigen-positive or E-antigen-negative RBC stroma.

CONCLUSION

A mimicking autoantibody with apparent E-antigen specificity was identified in the plasma sample of a woman with newly diagnosed ovarian cancer. Despite their relative low frequency, mimicking antibodies, whether auto- or alloantibodies, may interfere with the timely issuance of compatible blood products and may confuse laboratory and clinical staff. Determining the clinical significance of the antibody, by taking into account the RBC phenotype of the patient and the antigen prevalence in the general population, guides the extent of workup required to best utilize resources while assuring patient safety.

Auto-immune haemolytic anaemia and Crohn's disease: a case report and review of the literature

The association between ulcerative colitis and auto-immune haemolytic anaemia is well described. However, only two cases of auto-immune haemolytic anaemia occurring in association with Crohn's disease have been described in the literature. We report on a third case and discuss the importance of diagnosis and the therapeutic implications of this association.

Restriction in the repertoire of the immunoglobulin light chain subgroup in pathological cold agglutinins with anti-Pr specificity

BACKGROUND AND OBJECTIVES

In cold agglutinin disease, monoclonal red blood cell autoantibodies, termed cold agglutinins, induce haemolysis in patients exposed to the cold. Commonly, these autoantibodies are directed against the developmentally regulated I/i blood groups. A second blood group system, the Pr system (located on glycophorins), is involved less frequently. Anti-Pr cold agglutinins recognize either alpha 2,3- or alpha 2,6-linked N-acetylneuraminic acid as the immunodominant group. Cold agglutinins of anti-I/i specificity show a remarkable restriction in their genomic repertoire of the immunoglobulin heavy and light-chain immunoglobulin-variable domain (i.e. exclusive use of VH4-34 in heavy chains). For anti-Pr cold agglutinins, preliminary data on the repertoire of the light-chain variable domain indicate a preference for the subgroup Vkappa IV. To elucidate restrictions in the light-chain variable-domain subgroup repertoire of anti-Pr cold agglutinins systematically, and to discuss these results in the context of their anti-Pr(1-3) subclassification and immunodominant sialic acid, light chains in 13 anti-Pr cold agglutinins were investigated.

MATERIALS AND METHODS

The anti-Pr light chains were isolated using temperature-dependent absorption/elution techniques. Subsequently, they were subjected to N-terminal Edman degradation, and the light chain Vkappa subgroup was affiliated using the Kabat database.

RESULTS

Five of 13 (38%) light chains belonged to Vkappa IV, five of 13 (38%) to Vkappa I and three of 13 (23%) to Vkappa III. Anti-Pr with Vkappa IV subgroup light chains exclusively recognized alpha 2,3-linked N-acetylneuraminic acid.

CONCLUSIONS

Including data from the literature, the repertoire of the light-chain variable domain in pathological anti-Pr cold agglutinins exhibits a clear bias towards the use of the single germline gene-derived subgroup, Vkappa IV (eight of 17 or 47%). The association of Vkappa IV subgroup light chain-containing anti-Pr cold agglutinins with binding to alpha 2,3-, but not alpha 2,6-linked N-acetyneuraminic acid raises speculations about a possible role of subgroup-derived determinants in anti-Pr binding.

Autoantibody formation after alloimmunization: are blood tranfusions a risk factor for autoimmune hemolytic anemia?

BACKGROUND

The development of RBC autoantibodies resulting from or associated with allogeneic blood transfusions (i.e., RBC autoimmunization) is not a well-recognized complication of RBC transfusions.

STUDY DESIGN AND METHODS

T: he presentation, laboratory evaluation, clinical course, and management of two patients whose autoimmune hemolytic anemia followed allogeneic blood transfusion and occurred in association with the development of one or more alloantibodies is described. A retrospective analysis was performed of our blood-bank records over 1 year to determine the frequency of RBC autoimmunization associated with alloimmunization.

RESULTS

Out of 2618 patients who had a positive DAT or IAT, 121 were identified with RBC autoantibodies; 41 of these patients had both allo- and autoantibodies to RBC antigens, whereas the remainder, 80, had only autoantibodies. At least 34 percent (12/41) of these patients (none with hemoglobinopathy) developed their autoantibodies in temporal association with alloimmunization after recent blood transfusion(s).

CONCLUSION

RBC autoimmunization and the development of autoimmune hemolytic anemia should be recognized as a complication of allogeneic blood transfusion. The need for additional blood transfusion was successfully avoided in one patient by treatment with recombinant human EPO and corticosteroid therapy. Once RBC autoimmunization is identified, subsequent management should incorporate a strategy that minimizes subsequent exposure to allogeneic blood.

Glycophorin A-mediated haemolysis of normal human erythrocytes: evidence for antigen aggregation in the pathogenesis of immune haemolysis

The inexplicable severity of anti-Pr autoimmune haemolytic anaemia led us to test the hypothesis that the haemolysis was primarily due to a change in the function of glycophorin A, on which the Pr antigen is located. The lectins Maclura pomifera and wheat germ agglutinin that bind to glycophorin A induced the haemolysis of normal erythrocytes in vitro. Lectin binding led to an increase in erythrocyte membrane permeability to sodium and potassium, the former resulting in an influx of water and subsequent haemolysis. The response was glycophorin A specific as Concanavalin A, which binds to band 3, did not cause haemolysis and peanut agglutinin only did so after removal of erythrocyte sialic acid. The lectin-induced cation leak was not mediated by activation of cation channels as the inhibitors, tetrodotoxin, amiloride and 4,4' disothiocyanate stilbene 2,2'disulphonate, had no effect, suggesting that the haemolysis was due to exacerbation of the inherent cation permeability of the erythrocyte membrane. A human IgAK anti-Pr autoantibody and a mouse anti-human glycophorin A antibody increased erythrocyte permeability to sodium. The role of glycophorin A in stabilizing and, upon aggregation, destabilizing the phospholipid bilayer is discussed. Our findings may help explain the severity of anti-Pr autoimmune haemolytic anaemia and other pathophysiological changes in human erythrocytes.