Red cells coated with immunoglobulin G: binding and sphering by mononuclear cells in man

A Brief Chronicle of Antibody Research and Technological Advances

This review briefly traces the historical development of antibody research and related technologies. The path from early perceptions of immunity to the emergence of modern immunotherapy has been marked by pivotal discoveries and technological advances. Early insights into immunity led to the development of vaccination and serotherapy. The elucidation of antibody structure and function paved the way for monoclonal antibody technology and its application in diagnosis and therapy. Breakthroughs in genetic engineering have enabled the production of humanized antibodies and the advances in Fc engineering, thereby increasing therapeutic efficacy. The discovery of immune checkpoints and cytokines revolutionized the treatment of cancer and autoimmune diseases. The field continues to evolve rapidly with the advent of antibody-drug conjugates, bispecific antibodies, and CAR T-cell therapies. As we face global health challenges, antibody research remains at the forefront of medical innovation and offers promising solutions for the future.

The choice of new treatments in autoimmune hemolytic anemia: how to pick from the basket?

Autoimmune hemolytic anemia (AIHA) is defined by increased erythrocyte turnover mediated by autoimmune mechanisms. While corticosteroids remain first-line therapy in most cases of warm-antibody AIHA, cold agglutinin disease is treated by targeting the underlying clonal B-cell proliferation or the classical complement activation pathway. Several new established or investigational drugs and treatment regimens have appeared during the last 1-2 decades, resulting in an improvement of therapy options but also raising challenges on how to select the best treatment in individual patients. In severe warm-antibody AIHA, there is evidence for the upfront addition of rituximab to prednisolone in the first line. Novel agents targeting B-cells, extravascular hemolysis, or removing IgG will offer further options in the acute and relapsed/refractory settings. In cold agglutinin disease, the development of complement inhibitors and B-cell targeting agents makes it possible to individualize therapy, based on the disease profile and patient characteristics. For most AIHAs, the optimal treatment remains to be found, and there is still a need for more evidence-based therapies. Therefore, prospective clinical trials should be encouraged.

Novel insights into the treatment of complement-mediated hemolytic anemias

Complement-mediated hemolytic anemias can either be caused by deficiencies in regulatory complement components or by autoimmune pathogenesis that triggers inappropriate complement activation. In paroxysmal nocturnal hemoglobinuria (PNH) hemolysis is entirely complement-driven. Hemolysis is also thought to be complement-dependent in cold agglutinin disease (CAD) and in paroxysmal cold hemoglobinuria (PCH), whereas warm antibody autoimmune hemolytic anemia (wAIHA) is a partially complement-mediated disorder, depending on the subtype of wAIHA and the extent of complement activation. The pathophysiology, clinical presentation, and current therapies for these diseases are reviewed in this article. Novel, complement-directed therapies are being rapidly developed. Therapeutic terminal complement inhibition using eculizumab has revolutionized the therapy and prognosis in PNH but has proved less efficacious in CAD. Upstream complement modulation is currently being investigated and appears to be a highly promising therapy, and two such agents have entered phase II and III trials. Of these, the anti-C1s monoclonal antibody sutimlimab has shown favorable activity in CAD, while the anti-C3 cyclic peptide pegcetacoplan appears to be promising in PNH as well as CAD, and may also have a therapeutic potential in wAIHA.

ACVIM consensus statement on the diagnosis of immune-mediated hemolytic anemia in dogs and cats

Immune-mediated hemolytic anemia (IMHA) is an important cause of morbidity and mortality in dogs. IMHA also occurs in cats, although less commonly. IMHA is considered secondary when it can be attributed to an underlying disease, and as primary (idiopathic) if no cause is found. Eliminating diseases that cause IMHA may attenuate or stop immune-mediated erythrocyte destruction, and adverse consequences of long-term immunosuppressive treatment can be avoided. Infections, cancer, drugs, vaccines, and inflammatory processes may be underlying causes of IMHA. Evidence for these comorbidities has not been systematically evaluated, rendering evidence-based decisions difficult. We identified and extracted data from studies published in the veterinary literature and developed a novel tool for evaluation of evidence quality, using it to assess study design, diagnostic criteria for IMHA, comorbidities, and causality. Succinct evidence summary statements were written, along with screening recommendations. Statements were refined by conducting 3 iterations of Delphi review with panel and task force members. Commentary was solicited from several professional bodies to maximize clinical applicability before the recommendations were submitted. The resulting document is intended to provide clinical guidelines for diagnosis of, and underlying disease screening for, IMHA in dogs and cats. These should be implemented with consideration of animal, owner, and geographical factors.

In utero electroporation induces cell death and alters embryonic microglia morphology and expression signatures in the developing hypothalamus

Background

Since its inception in 2001, in utero electroporation (IUE) has been widely used by the neuroscience community. IUE is a technique developed to introduce plasmid DNA into embryonic mouse brains without permanently removing the embryos from the uterus. Given that IUE labels cells that line the ventricles, including radial fibers and migrating neuroblasts, this technique is an excellent tool for studying factors that govern neural cell fate determination and migration in the developing mouse brain. Whether IUE has an effect on microglia, the immune cells of the central nervous system (CNS), has yet to be investigated.

Methods

We used IUE and the pCIG2, pCIC-Ascl1, or pRFP-C-RS expression vectors to label radial glia lining the ventricles of the embryonic cortex and/or hypothalamus. Specifically, we conducted IUE at E14.5 and harvested the brains at E15.5 or E17.5. Immunohistochemistry, along with cytokine and chemokine analyses, were performed on embryonic brains with or without IUE exposure.

Results

IUE using the pCIG2, pCIC-Ascl1, or pRFP-C-RS vectors alone altered microglia morphology, where the majority of microglia near the ventricles were amoeboid and displayed altered expression signatures, including the upregulation of Cd45 and downregulation of P2ry12. Moreover, IUE led to increases in P2ry12⁻ cells that were Iba1⁺/IgG⁺ double-positive in the brain parenchyma and resembled macrophages infiltrating the brain proper from the periphery. Furthermore, IUE resulted in a significant increase in cell death in the developing hypothalamus, with concomitant increases in cytokines and chemokines known to be released during pro-inflammatory states (IL-1β, IL-6, MIP-2, RANTES, MCP-1). Interestingly, the cortex was protected from elevated cell death following IUE, implying that microglia that reside in the hypothalamus might be particularly sensitive during embryonic development.

Conclusions

Our results suggest that IUE might have unintended consequences of activating microglia in the embryonic brain, which could have long-term effects, particularly within the hypothalamus.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1213-6) contains supplementary material, which is available to authorized users.

Complement Activation and Inhibition in Autoimmune Hemolytic Anemia: Focus on Cold Agglutinin Disease

The classical complement pathway and, to some extent, the terminal pathway, are involved in the immune pathogenesis of autoimmune hemolytic anemia (AIHA). In primary cold agglutinin disease (CAD), secondary cold agglutinin syndrome and paroxysmal cold hemoglobinuria, the hemolytic process is entirely complement dependent. Complement activation also plays an important pathogenetic role in some warm-antibody AIHAs, especially when immunoglobulin M is involved. This review describes the complement-mediated hemolysis in AIHA with a major focus on CAD, in which activation of the classical pathway is essential and particularly relevant for complement-directed therapy. Several complement inhibitors are candidate therapeutic agents in CAD and other AIHAs, and some of these drugs seem very promising. The relevant in vitro findings, early clinical data and future perspectives are reviewed.

Warm antibody autoimmune hemolytic anemia

Autoimmune hemolytic anemia (AIHA) is a rare and heterogeneous disease that affects 1 to 3/100 000 patients per year. AIHA caused by warm autoantibodies (w-AIHA), ie, antibodies that react with their antigens on the red blood cell optimally at 37°C, is the most common type, comprising ∼70% to 80% of all adult cases and ∼50% of pediatric cases. About half of the w-AIHA cases are called primary because no specific etiology can be found, whereas the rest are secondary to other recognizable underlying disorders. This review will focus on the postulated immunopathogenetic mechanisms in idiopathic and secondary w-AIHA and report on the rare cases of direct antiglobulin test-negative AIHA, which are even more likely to be fatal because of inherent characteristics of the causative antibodies, as well as because of delays in diagnosis and initiation of appropriate treatment. Then, the characteristics of w-AIHA associated with genetically defined immune dysregulation disorders and special considerations on its management will be discussed. Finally, the standard treatment options and newer therapeutic approaches for this chronic autoimmune blood disorder will be reviewed.

Role of Complement in Autoimmune Hemolytic Anemia

The classification of autoimmune hemolytic anemias and the complement system are reviewed. In autoimmune hemolytic anemia of the warm antibody type, complement-mediated cell lysis is clinically relevant in a proportion of the patients but is hardly essential for hemolysis in most patients. Cold antibody-mediated autoimmune hemolytic anemias (primary cold agglutinin disease, secondary cold agglutinin syndrome and paroxysmal cold hemoglobinuria) are entirely complement-mediated disorders. In cold agglutinin disease, efficient therapies have been developed in order to target the pathogenic B-cell clone, but complement modulation remains promising in some clinical situations. No established therapy exists for secondary cold agglutinin syndrome and paroxysmal cold hemoglobinuria, and the possibility of therapeutic complement inhibition is interesting. Currently, complement modulation is not clinically documented in any autoimmune hemolytic anemia. The most relevant candidate drugs and possible target levels of action are discussed.

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.

Red blood cell destruction in autoimmune hemolytic anemia: role of complement and potential new targets for therapy

Autoimmune hemolytic anemia (AIHA) is a collective term for several diseases characterized by autoantibody-initiated destruction of red blood cells (RBCs). Exact subclassification is essential. We provide a review of the respective types of AIHA with emphasis on mechanisms of RBC destruction, focusing in particular on complement involvement. Complement activation plays a definitive but limited role in warm-antibody AIHA (w-AIHA), whereas primary cold agglutinin disease (CAD), secondary cold agglutinin syndrome (CAS), and paroxysmal cold hemoglobinuria (PCH) are entirely complement-dependent disorders. The details of complement involvement differ among these subtypes. The theoretical background for therapeutic complement inhibition in selected patients is very strong in CAD, CAS, and PCH but more limited in w-AIHA. The optimal target complement component for inhibition is assumed to be important and highly dependent on the type of AIHA. Complement modulation is currently not an evidence-based therapy modality in any AIHA, but a number of experimental and preclinical studies are in progress and a few clinical observations have been reported. Clinical studies of new complement inhibitors are probably not far ahead.

Effect of vasodilators in patient with pulmonary hypertension associated with hemolytic anemia

Pulmonary arterial hypertension (PAH) has been described to associate with hemolytic anemia in updated clinical classification of pulmonary hypertension. A 56-year-old woman, diagnosed with warm antibody autoimmune hemolytic anemia (AIHA), was treated with oral corticosteroids at the Department of Hematology, Osaka University Hospital for 30 years. Her AIHA worsened 3 months before the admission, and she was treated with rituximab and cyclosporine in combination with prednisolone. Soon after she left the hospital, she developed dyspnea on effort and leg edema, therefore she was re-admitted to the Department of Cardiovascular Medicine. Echocardiogram and cardiac catheterization demonstrated PAH associated with AIHA. She was treated with three types of vasodilatory agents, resulting in an improvement in pulmonary arterial pressure and pulmonary vascular resistance after 6 weeks. A few weeks after she left the hospital, her hemolytic anemia became in remission without intensifying AIHA therapy, and did not worsen for a year of follow-up. Although corticosteroids are the first-line treatment for AIHA, medications for PAH should be considered when the first-line therapy for AIHA failed to improve PAH.

Quantitative immunology of immune hemolytic anemia: II. The relationship of cell-bound antibody to hemolysis and the effect of treatment

The concentration of cell-bound and serum antibody was determined in a series of patients with warm antibody immune hemolytic anemia by determining the amount of C[unk]1 fixed to the cells by anti-IgG. This was compared to the rate of hemolysis as determined by hemoglobin concentration and reticulocyte count, or the endogenous production of carbon monoxide. The rate of hemolysis was, in general, proportional to the concentration of cell-bound antibody. In splenectomized patients, the rate of hemolysis was very much less than in unsplenectomized patients for a given concentration of cell-bound antibody. When prednisone was given, three effects were noted: (a) at high doses of drug, the concentration of cell-bound antibody decreased rapidly and the concentration of serum antibody increased, suggesting that the affinity of antibody for antigen had been altered; (b) in patients achieving remission, the concentration of serum antibody fell to low levels but rose again if the dose of prednisone was insufficient; (c) in one patient, prednisone appeared to inhibit sequestration of highly sensitized cells.

Rosetting, phagocytosis and immune red cell damage

Observations on rosette formation of red blood cells sensitized with a known number of IgG1 or IgG3 polyclonal or monoclonal anti-Rh(D) antibodies with monocytes, lymphocytes and granulocytes have provided further evidence for the essential role of monocytes/macrophages in red cell destruction. The rosette test with monocytes and the monocyte-monolayer assay (MMA) have confirmed, on a quantitative basis, the greater binding ability of IgG3 than of IgG1 antibodies and that the rate of interaction with red cells increases in proportion to the level of their sensitization. These observations have suggested that the MMA may reflect haemolysis in vivo. It has appeared that the MMA is suitable for assessing haemolysis in many cases of haemolytic disease of the newborn, in autoimmune haemolytic anaemia and in patients with alloantibodies to be transfused. Since in individual cases a clear correlation between the MMA results and haemolysis in vivo was not observed, the factors which may influence such discrepancies are discussed.

Hemolytic anemia due to warm autoantibodies

The diagnosis of autoimmune hemolytic anemia (AHA) requires evidence of shortened red blood cell (RBC) survival mediated by autoantibodies directed against autologous RBCs. About 80 percent of patients with AHA have warm-reactive antibodies of the IgG isotype; the remainder exhibit cold-reactive autoantibodies. Typical patients exhibit anemia, reticulocytosis, spherocytes and polychromasia on the blood film and a positive direct antiglobulin test (DAT). Increased indirect serum bilirubin, urinary urobilinogen and serum lactate dehydrogenase (LDH), and decreased serum haptoglobin are not required for the diagnosis, but are frequently present. Patients with AHA and no underlying associated disease are said to have primary or idiopathic AHA. AHA in patients with associated autoimmune disease and certain malignant or infectious diseases is classified as secondary. The etiology of AHA is unknown. Patients with symptomatic anemia require transfusion of RBCs. Prednisone and splenectomy may provide long term remission. Rituximab, intravenous immunoglobulin, immunosuppressive drugs and danazol have been effective in refractory cases and for patients who are poor candidates for surgery.

Incidence of hereditary spherocytosis in a population of jaundiced neonates

As most of hereditary spherocytosis-affected individuals experience jaundice at birth, it seemed of interest to evaluate the proportion of hereditary spherocytosis in 402 severely jaundiced neonates with a bilirubinemia level prompting phototherapy. Red cell dehydration, a hallmark of spherocytosis whether constitutional or acquired, was demonstrated in 74 of them, among whom 23 disclosed a typical pattern of spherocytosis upon red cell deformability studies. Acquired spherocytosis of immune origin was diagnosed in 19/23 and hereditary spherocytosis in 4, making the proportion of hereditary spherocytosis-affected individuals among a severely jaundiced population of neonates amount to 1%, an incidence at least 30-fold that of the overall population.

Boston City Hospital and the Thorndike Memorial Laboratory: the birth of modern haematology

Established in 1923, the Thorndike Memorial Laboratory at Boston City Hospital was the first clinical research laboratory in a municipal hospital in the United States of America. Minot and Castle, who were the second and third directors of the Laboratory, were pioneer haematologists and clinical investigators of the highest calibre who created an atmosphere at the Laboratory that would foster patient-centred research and attract the best physician-scientists to work and train there. The haematology research division of the Laboratory made important original contributions to the understanding of the pathophysiology of anaemia, the mechanisms of red cell and platelet destruction and the phagocytic role of the spleen, the nature of haemoglobin (normal and sickle cell), the nature of haemophilia and its therapy and the early classification of lymphoma. It contributed to the Thorndike Memorial Laboratory's worldwide reputation as a model research laboratory and established its reputation as the birthplace of modern haematology.

Autoimmune hemolytic anemia

Red blood cell (RBC) autoantibodies are a relatively uncommon cause of anemia. However, autoimmune hemolytic anemia (AIHA) must be considered in the differential diagnosis of hemolytic anemias, especially if the patient has a concomitant lymphoproliferative disorder, autoimmune disease, or viral or mycoplasmal infection. Classifications of AIHA include warm AIHA, cold agglutinin syndrome, paroxysmal cold hemoglobinuria, mixed-type AIHA, and drug-induced AIHA. Characteristics of the autoantibodies are responsible for the various clinical entities. As a result, diagnosis is based on the clinical presentation and a serologic work-up. For each classification of AIHA, this review discusses the demographics, etiology, clinical presentation, laboratory evaluation, and treatment options.

Temporal differences in membrane loss lead to distinct reticulocyte features in hereditary spherocytosis and in immune hemolytic anemia

Spherocytic red cells with reduced membrane surface area are a feature of hereditary spherocytosis (HS) and some forms of autoimmune hemolytic anemia (AIHA). It is generally assumed that membrane loss in spherocytic red cells occurs during their sojourn in circulation. The structural basis for membrane loss in HS is improper assembly of membrane proteins, whereas in AIHA it is due to partial phagocytosis of circulating red cells by macrophages. A hypothesis was formed that these different mechanisms should lead to temporal differences in surface area loss during red cell genesis and during sojourn in circulation in these 2 spherocytic syndromes. It was proposed that cell surface loss could begin at the reticulocyte stage in HS, whereas surface area loss in AIHA involves only circulating mature red cells. The validity of this hypothesis was established by documenting differences in cellular features of reticulocytes in HS and AIHA. Using a novel technique to quantitate cell surface area, the decreased membrane surface area of both reticulocytes and mature red cells in HS compared with normal cells was documented. In contrast, in AIHA only mature red cells but not reticulocytes exhibited decreased membrane surface area. These data imply that surface area loss in HS, but not in AIHA, is already present at the circulating reticulocyte stage. These findings imply that loss of cell surface area is an early event during genesis of HS red cells and challenge the existing concepts that surface area loss in HS occurs predominantly during the sojourn of mature red cells in circulation.

Expression of HLA-ABC and -DR locus antigens on human kidney, endothelial, tubular and glomerular cells

The distribution of the major histocompatibility complex antigens on the various cellular structures of the human kidney was analysed by using a modified Staphylococcus aureus Cowan 1 method. Conventional alloantisera and heterologous antisera raised against isolated molecules were used for the HLA-ABC antigens, whereas the HLA-DR (Ia) antigens were detected with heterologous antisera only. The HLA-ABC antigens were expressed on all types of kidney passenger leucocytes, on vascular endothelial cells, and on kidney tubular cells, but not substantially on the glomerular podocytes. The DR antigens were strongly expressed on (a fraction of) the passenger lymphocytes and on the kidney vascular endothelial cells, weakly on the passenger monocytes, but not measurably on the urine-producing apparatus of the kidney--that is, on the glomerular and tubular cells.

Ultrastructural changes of tissues produced by inhalation of thinner in rats

Thinner is a substance that is used for industrial purposes and for drug abuse; addiction is of young people (average age, 7.5 years). Although the health problem of voluntary or nonvoluntary solvent sniffing is important, great attention has been paid to the epidemiology and pharmacology of paint thinner or industrial solvents inhalation, but studies at the morphological and biochemical level are scarce. This work describes the morphological changes in the lung, liver, kidney, adrenal glands, and central nervous system induced by short- (up to 4 weeks) and long-term (up to 14 weeks) periods of thinner inhalation in rats.

Autoimmune haemolysis in the dog: relationship between anaemia and the levels of red blood cell bound immunoglobulins and complement measured by an enzyme-linked antiglobulin test

A direct enzyme-linked antiglobulin test (DELAT) was used to measure the levels of red blood cell (RBC) bound IgG, IgM, IgA and C3 in dogs with autoimmune haemolytic anaemia (AIHA). At presentation, one or more DELAT parameters was raised in each AIHA case, and the RBC were typically coated with immunoglobulin of more than one class, together with C3. There was no relationship between the levels of RBC-bound IgG, IgM or IgA and the severity of the anaemia, although a significant negative correlation (rs = -0.66, P < 0.02) was found between bound C3 and blood haemoglobin concentration. These results indicate that the level of sensitisation of erythrocytes with IgG alone is not a reliable predictor of the severity of haemolysis in different cases, and that the pathogenesis of AIHA can be complex, involving multiple immunoglobulin classes and complement in the destruction of RBC. A significant relationship (rs = 0.63, P < 0.02) was found between serum IgG concentration and haemoglobin levels, and it is suggested that this may be due to free IgG inhibiting the interaction of IgG-sensitised RBC with macrophages. Serial measurements from individual AIHA cases during treatment revealed that the levels of RBC-bound immunoglobulins fell simultaneously with improvements in anaemia. In one dog, a relapse was associated with increases in bound IgG and IgM. Transient relative reticulocytopenia at presentation was common, but was not related to the severity of the anaemia. However, in other cases there was a persistent failure to increase RBC production, which was associated with slower recovery.

Alloimmune conditions and pregnancy

Transfer of fetal red blood cells and platelets to the maternal circulation can stimulate an immune response with production of immunoglobulin that can cross the placenta. Similarly, passage of maternal stem cells to an immunologically incompetent fetus can theoretically produce graft-versus-host disease. disease. Maternal sensitization to red blood cell antigens such as D and Kell can result in anaemia, hydrops, and death in an incompatible fetus. Current assessment of these pregnancies involves serial analysis of amniotic fluid bilirubin concentration, with umbilical cord blood sampling reserved for special circumstances; neither ultrasound or Doppler blood flow analysis are accurate in the prediction of fetal haematocrit. Intravascular transfusion is the treatment of choice for hydropic fetuses. Perinatal survival in non-hydropic fetuses is similar with either intravascular or intraperitoneal transfusion, and the choice of procedures is individualized. Isoimmune fetal thrombocytopenia is usually the result of maternal sensitization to the PlA1 antigen. There is significant risk of intracranial haemorrhage, both antepartum and during labour and delivery. Umbilical cord blood sampling at term can determine fetal platelet count and the need for platelet transfusion, and can aid in deciding the appropriate route of delivery.

Hemolytic anemias. Diagnosis and management

Hemolysis can be induced by two general mechanisms. In the first one, erythrocytes lyse intravascularly due to complement fixation, trauma, or other extrinsic factors. In the second mechanism, which is the most common, the red cells are removed from the circulation by the mononuclear-phagocytic system either because they are intrinsically defective or because of the presence of bound immunoglobulins to their surfaces. The diagnosis of hemolysis is not difficult to establish and is based on the presence of anemia with sustained reticulocytosis in the absence of blood loss. Additional findings can include marrow erythroid hyperplasia; increased unconjugated bilirubin, LDH, and free hemoglobin; decreased haptoglobin and hemopexin; hemoglobinuria and hemosiderinuria; and decreased 51Cr red cell half-life. Hemoglobinemia, hemoglobinuria, and hemosiderinuria occur only in the setting of severe and rapid intravascular hemolysis. Conditions associated with significant lysis of red cells in the circulation include incompatible transfusion, G6PD deficiency, PNH, severe burns, and certain infections. The morphology of the red cell is abnormal in almost all cases of hemolytic anemia. However, the morphologic abnormality can be, in certain cases, diagnostic of the underlying condition. Treatment is usually supportive, with effective therapy directed to treat the underlying cause of hemolysis.

Evidence for immune-mediated destruction as mechanism for LCMV-induced anemia in persistently infected mice

A docile substrain of lymphocytic choriomeningitis virus (LCMV) causes a persistent infection in adult C3HeB mice and induces a severe anemia, which, unlike the viremia, eventually resolves. Measurements of red blood cell (RBC) survival rates demonstrated an increased rate of RBC clearance in these animals, indicating a hemolytic process for the anemia. Normal clearance rates of RBCs from infected mice transfused into control mice suggested that there was not an intrinsic defect in these cells. It also appeared that RBC destruction was immune-mediated, as cyclophosphamide treatments prevented the onset of anemia in infected mice, whereas adoptive transfer (AT) of immune splenocytes into immunocompromised mice reestablished the condition. The AT experiments also demonstrated that the onset of anemia correlated with the functional state of the immune cells. In addition, opsonization of RBCs was demonstrated by macrophage phagocytosis, and the appearance of opsonized RBCs corresponded with the course of the anemia. These findings support a hypothesis of RBC opsonization and subsequent phagocytosis by macrophages of the reticuloendothelial system as the mechanism for RBC destruction in LCMV-induced hemolytic anemia.

Surface receptors and immune activity of purified human circulating mononuclear cells. V. Circulating null cells and a factor secreted by the null cells inhibit the synthesis of receptors for Fc mu by T cells in culture

Receptors for Fc mu (Fc mu R) were not detected on freshly isolated unfractionated circulating human mononuclear cells (MNC) or purified T cells. However, a significant percentage of the T cells (20% to 40%), but not of the unfractionated MNC, exhibited Fc mu receptors following culture for 24 h at 37 degrees C in medium enriched with fetal calf serum. These receptors were newly synthesized by the T cells since they were not detected on T cells cultured for 24 h with cycloheximide in a non-cytotoxic concentration. The absence of Fc mu R on the cultured unfractionated MNC (of which 70% are T cells) suggested that non-T cells within the MNC-B cells and/or null cells and/or monocytes suppressed the synthesis of Fc mu R by the T cells. These cells were individually assayed for their capacity to suppress Fc mu R synthesis by co-cultured T cells. The null cells were able to totally suppress Fc mu R synthesis whereas the B cells and monocytes exhibited no suppressive activity. Null cells cultured for 24 h at 37 degrees C secreted a factor which inhibited the synthesis of receptors for Fc mu by the cultured T cells. This factor is referred to as receptor synthesis suppressor factor or RSSF. On the basis of these findings, it is concluded that (a) the circulating T cells do not possess Fc mu R; these receptors are synthesized de novo by the T cells in culture, (b) the null cells, but neither the B cells nor the monocytes, suppress the synthesis of the Fc mu R by the T cells and (c) the null cells, but neither the B cells nor the monocytes, secrete a factor, receptor synthesis suppressor factor, which can suppress the synthesis of Fc mu R by the T cells.

Evidence that the phagocytosis mediated by the peanut agglutinin-like activity of IgG(Fc) receptors of human monocytes is selectively modulated by estradiol and natural estrogens

The percentage of human monocytes (MCs) that are able to form rosettes with, and to phagocytose, IgG-coated sheep red blood cells (IgG-SRBCs) has been first determined in vitro by a classical rosette assay in 12 postmenopausal (PM) women. Half of them never received any suppletive estrogen (E) therapy at the time of testing, whereas the other six were chronically treated with E. Three different preparations of the same anti-SRBC IgG antibody batch were coated to SRBCs: the first one was the starting antibody preparation [IgG(total] and the other two were purified by affinity chromatography either on Sepharose-concanavalin A (Con A) or on agarose-peanut agglutinin (PNA) columns specifically recognizing terminal, and/or accessible, alpha-mannosyl [IgG(Con A)] or beta-galactosyl [IgG(PNA)] residues of the Fc domain, respectively. The three IgG preparations exhibited similar hemagglutinating antibody titers (1/100). All experiments were conducted using a coating range of 5000 to 6000 IgG antibody molecules per SRBC. In PM women with E, the rosetting capacity of autologous MCs (percentage of MCs rosetting at least three IgG-SRBCs), their phagocytosing capacity (percentage of MCs ingesting at least three IgG-SRBCs), and the phagocytosis index (number of SRBCs ingested/100 MCs) were similar for each IgG-SRBC preparation considered. In contrast, in PM women without E, the capacity of MCs to phagocytose IgG(PNA)-SRBCs, as well as the phagocytosis index measured with those SRBCs, was strongly reduced (P less than 0.01 at least), when compared to the same parameters determined using IgG(total)-SRBCs and IgG(Con A)-SRBCs.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of serious alloimmunization in pregnancy

In the past 40 years, tremendous advances in the treatment of hemolytic disease have been made. The perinatal mortality has been reduced considerably. Rh immunoprophylaxis has decreased the incidence of Rh immunization to around 6 per 100,000 live births. Nevertheless, treatment of severe hemolytic disease is still essential. Increased reliability of diagnostic procedures have made early detection and optimal treatment of hemolytic disease possible. Treatment by plasmapheresis is still controversial. Although believed to be beneficial by some authors, conclusive evidence of its efficacy has not been obtained. With preterm induction of birth at 32 weeks of gestation, the chances for survival are 95%. Improvement of techniques and the use of modern real-time ultrasound equipment have made intrauterine intraperitoneal transfusion, in experienced hands, a relatively safe and successful procedure. Intravascular transfusion appears beneficial in early pregnancy. Combination of both techniques will probably be the answer for the future. The development of neonatal intensive care facilities has made a major contribution to the survival of children with haemolytic disease. The relative low incidence of haemolytic disease has made it imperative that treatment should take place in centers where experience and special skill are available.

A transient monocyte defective function in idiopathic nephrotic syndrome (lipoid nephrosis)

Alterations in phagocytosis have been studied in 25 patients with idiopathic nephrotic syndrome (INS). At the time of investigation all patients had normal renal function.

Optical microscopy of antibody-dependent phagocytosis and lysis of erythrocytes by living normal and chronic granulomatous disease neutrophils: a role of superoxide anions in extra- and intra-cellular lysis

Novel optical microscopic techniques have been developed to observe neutrophil-mediated effector functions at the level of individual cells. Conventional absorption spectrophotometry has shown that exposure of hemoglobin to superoxide anions decreases the intensity of the Soret band and shifts it to lower wavelengths. This oxidative event can be visualized within intact erythrocytes using bright-field microscopy in conjunction with violet illumination at 430 nm. The sequential oxidation of IgG-opsonized sheep erythrocytes bound to normal human neutrophils can be observed. Chronic granulomatous disease (CGD) neutrophils which do not generate superoxide anions were not capable of influencing target absorption at 430 nm. Cytolytic events were visualized by fluorescence microscopy. Cytosolic or membrane compartments of sheep erythrocytes were labeled with eosin Y or fluorescein isothiocyanate, respectively. Time-dependent studies of erythrolysis show that targets are lysed extra- and intra-cellularly. The fluorescent diffusion gradient generated at the site of membrane rupture suggests that a pore of approximately 30 nm in diameter is formed in the target membrane. The site of pore formation is not found at the target-effector cell interface. CGD neutrophils did not display these cytolytic phenomena. Furthermore, the cytosolic label eosin Y could be followed into an associated granule compartment; we suggest that the phenomenon of piranhalysis may participate in antibody-dependent effector mechanisms. Phagocytosis can also be observed using fluorescently-labeled erythrocytes. Determinations of phagocytic index are more reliable with this approach. These microscopical methods are both simple and efficient. To our knowledge, these are the first direct microscopic studies of effector cell-mediated target cell oxidation and cytolysis. These experiments provide a fresh approach to the study of phagocyte effector functions at the cellular level and illuminate the importance of superoxide anions in antibody-dependent erythrolysis.

Effect of commercial immunoglobulin G preparation on human monocyte Fc-receptor dependent binding of antibody coated platelets

This study examined the in vitro effect of a commercial immunoglobulin preparation on human monocytes and the Fc-receptor dependent binding of antibody coated platelets. Monocytes were exposed to Sandoglobulin in vitro and subsequently examined for membrane surface bound IgG. Dramatic increments of surface IgG were found which were maximal with 18 h exposure and somewhat higher at 4 degrees C than 37 degrees C. Ultracentrifugations of Sandoglobulin immediately prior to monocyte exposure reduced the monocyte membrane IgG by 75%. The 18 h exposure at 37 degrees C produced dramatic impairment of monocyte Fc-receptor binding of IgG coated platelets (P less than 0.001) while exposure for 18 h at 4 degrees C produced a modest impairment of Fc-receptor function. These studies indicate that Sandoglobulin contains IgG aggregates which are able to firmly bind to the monocyte surface in a time and temperature dependent fashion. The dramatic impairment of Fc-receptor function at 37 degrees C and not at 4 degrees C suggests that Fc-receptor modulation, as well as competitive inhibition/steric hindrance, contribute to impairment of monocyte Fc-receptor function.

Reversal of autoimmune hemolytic anemia associated with chronic lymphocytic leukemia following high-dose immunoglobulin

An 85-year-old man with chronic lymphocytic leukemia developed severe warm antibody-type autoimmune hemolytic anemia. Initial therapy with high-dose corticosteroids had no discernible effect on the hemolytic process. Following treatment with high-dose intravenous immunoglobulin (0.4 g/kg/d for 5 consecutive days) there was an immediate and sustained increase in hematocrit accompanied by a progressive decline in reticulocyte count. A review of the literature reveals that some patients with steroid-resistant immune hemolysis may benefit from high-dose immunoglobulin. This approach should be considered in elderly patients with severe anemia whose medical status precludes splenectomy.

Fetal blood sampling in Rh hemolytic disease

Fetal blood sampling under ultrasound guidance has added a new dimension to the management of Rh hemolytic disease. Combined with the established parameters of history, antibody measurement and amniotic fluid delta OD450 readings, direct testing of the blood of the fetus completes the picture. As well as giving information that may be applied to decisions regarding management, an opportunity is provided to observe the mechanism of anti-D IgG-induced red cell destruction in vivo.

The spontaneous ability of normal human IgG to inhibit the Fc receptors of normal human monocytes is related to their binding capacity to lectins

The lectin-binding capacity of 96 normal human IgG, assessed by solid-phase radioimmunoassay, strikingly varied according to the lectin considered. Indeed, half of the IgG samples exhibited peanut agglutinin (PNA)- and pokeweed mitogen-specific binding capacities superior or equal to 4%, whereas less than 15% of IgG similarly bound to concanavalin A (Con A) and to phytohemagglutinin. The ability of those IgG to inhibit the Fc receptor (Fc-R) function of human monocytes, measured by a classical rosette assay, was inversely correlated to their binding ratios to PNA and Con A only. By affinity chromatography, three groups of IgG were separated: the IgG purified on agarose-PNA columns slightly reduced the Fc-R function (40-45% inhibition); the IgG purified on Sepharose-Con A columns exhibited the highest inhibitory properties (80-85% inhibition); the IgG that did not bind to PNA and Con A columns possessed intermediate inhibitory properties (65-70% inhibition). The different effect of IgG on Fc receptors was conserved when monocytes were first treated by trypsin and was unrelated to their specific binding to human monocytes, to their subclasses, and to their C1q- or protein A-binding capacities. Incubation of monocytes with D-galactose (10 mM) significantly improved their capacity to form IgG rosettes, whereas their incubation with D-mannose (10 mM) significantly reduced the Fc-R function. Scatchard plots of 125I-IgG1 myeloma protein binding to monocytes were linear under basal conditions, as well as after a prior incubation of the cells with D-galactose or D-mannose. Monocytes bound about 16,000 molecules of IgG1 per cell in each instance. In contrast, the mean association constant (Ka) for IgG1 binding was 2.59 +/- 0.50 X 10(8) M-1 under basal conditions, 4.4 +/- 0.75 X 10(8) M-1 after D-galactose incubation, and 1.35 +/- 0.50 X 10(8) M-1 after D-mannose incubation. These data suggest that the level of human monocyte Fc-R function blockade induced by human IgG depends mainly on the presence of "accessible" galactosyl or mannosyl residues in the Fc domain and that the modulation of the Fc-R function induced by these carbohydrates is due to a change in the affinity rather than in the number of single class of high-affinity binding sites.