Chronic hemolytic anemia due to cold agglutinins: the mechanism of resistance of red cells to C' hemolysis by cold agglutinins

Initiation and regulation of complement during hemolytic transfusion reactions

Hemolytic transfusion reactions represent one of the most common causes of transfusion-related mortality. Although many factors influence hemolytic transfusion reactions, complement activation represents one of the most common features associated with fatality. In this paper we will focus on the role of complement in initiating and regulating hemolytic transfusion reactions and will discuss potential strategies aimed at mitigating or favorably modulating complement during incompatible red blood cell transfusions.

Clinical application of a flow cytometric direct antiglobulin test

BACKGROUND

The clinical application of flow cytometric direct antiglobulin test (FC-DAT) has rarely been evaluated for patients with various diseases including immune and nonimmune hemolytic anemia.

STUDY DESIGN AND METHODS

Blood samples from 380 patients with a variety of diseases were studied using the tube direct DAT and FC-DAT. The results of tube DAT and FC-DAT were compared. The predictive values of DAT for hemolysis were evaluated.

RESULTS

Of 57 patients with autoimmune hemolytic anemia (AIHA), 6 of the 17 with a negative tube DAT (immunoglobulin G [IgG]) had a positive FC-DAT (IgG) and 23 of the 36 patients with a negative tube DAT (complement 3d [C3d]) had a positive FC-DAT (C3d). In 57 patients with AIHA, the incidence of positive results of FC-DAT (IgG) and tube DAT (IgG) were similar (42 positive vs. 40 positive); but in 323 patients without AIHA, the incidence of positive FC-DATs (IgG) was higher than that of tube DAT (IgG; 47 positive vs. 9 positive). The higher incidence of positive FC-DAT (C3d) than that of tube DAT (C3d) was seen in patients with AIHA (42 positive vs. 21 positive) as well as in patients without AIHA (61 positive vs. 5 positive). Both DAT (IgG) and DAT (C3d) positive has highest positive predictive value for hemolysis, followed by DAT (IgG) alone positive and DAT (C3d) alone positive.

CONCLUSIONS

FC-DAT is a complementary test for diagnosing AIHA. There is a synergistic effect of the red blood cell-bound IgG and complement in predicting hemolysis.

Inefficacy of plasma exchange in cold agglutinin hemolytic anemia--a case study

A therapeutic trial of plasma exchange was conducted in an 82-year-old woman with severe cold agglutinin hemolytic anemia, who was unresponsive to conventional treatment. In spite of considerable improvement of pertinent parameters (total IgM, cold agglutinin titer and thermal amplitude) this treatment failed to induce a clinical remission. This failure may be the result of the ability of the cold agglutinin to fix complement to the red cell membrane at temperatures much higher than the thermal amplitude. A simple laboratory test to detect this dissociation between complement fixing ability and agglutination activity is described.

Increased efficiency of binding of nascent C3b to the erythrocytes of chronic cold agglutinin disease

The pathogenesis of chronic cold agglutinin disease (CCAD) has been enigmatic. To determine if abnormal erythrocyte membrane constituents might provide the stimulus for antibody production, we compared the electrophoretic pattern of radiolabeled membrane glycoproteins of four patients with CCAD to that of normal control erythrocytes. For the CCAD erythrocytes, fluorographs revealed the appearance of an abnormal band whose molecular weight was estimated at 126,000 D. Using two-dimensional gel analysis and immunoblotting techniques, it was determined that the 126,000 D glycoprotein consisted predominately of polymeric glycophorin-alpha. Previous investigations had suggested that abnormalities in glycophorin-alpha influence the functional activity of the complement system. When purified complement (C)3 was activated in the fluid-phase by cobra venom factor complexes, CCAD erythrocytes bound nascent C3b 7-27 times more efficiently than normal erythrocytes. Normal erythrocytes could be induced to manifest the appearance of the 126,000 D band, and the increased efficiency of binding of nascent C3b by incubation with CCAD serum or with the purified cold agglutinin antibody plus autologous serum, but not with the purified antibody alone or the purified antibody plus EDTA-chelated autologous serum. These studies demonstrate that the interactions of IgM cold-reacting antibody and complement with glycophorin induce changes in the biophysical properties of the erythrocyte membrane which modify subsequent interactions with complement.

The effect of hypothermic cardiopulmonary bypass on patients with low-titer, nonspecific cold agglutinins

The effect of hypothermic cardiopulmonary bypass (CPB) was studied in 5 patients with strongly positive cold agglutination at 4 degrees C (experimental group) and in 10 controls. In the in vitro part of the study, the characteristics of the cold agglutinin antibodies in the experimental group included a low thermal amplitude (28 degrees C or less), a low 4 degrees C agglutination titer (1:32 or less), and nonspecificity (non-anti-I and non-anti-i). The in vivo portion of the study revealed a fall in total urine and serum free hemoglobin in both groups on going on bypass, followed by a rise for the remainder of bypass. Statistical comparison between observed and expected total free hemoglobin for both groups showed a significant rise (p less than 0.05) after bypass, thereby indicating ongoing hemolysis. No statistically significant difference between preoperative and post-operative blood urea nitrogen and creatinine levels and gross neurological status was observed in the experimental group. It was concluded that the patient with nonspecific cold agglutinins whose antibody is characterized by a low titer, a low thermal amplitude, and a lack of clinical symptomatology can undergo hypothermic CPB without increased threat of a hemolytic or vascular occlusive crisis.

Transient Donath-Landsteiner haemolytic anaemia

Five children with 'paroxysmal cold haemoglobinuria' are described. In all of them an upper respiratory tract infection preceded the episode of acute intravascular haemolysis and potentially pathogenic organisms were recovered from four. The haematological features are presented and the importance of technique in the detection of the pathognomonic antibody is stressed and discussed in detail. Although the clinical manifestations are usually self-limiting and of short duration, it may be necessary, because of the rapidity and severity of anaemia, to provide interim support with appropriate blood transfusion. Since the disease is not usually recurrent and not clearly related to exposure to cold, it is suggested that it be re-named Donath-Landsteiner haemolytic anaemia.

Autoimmune hemolytic anemia

In autoimmune hemolytic anemia, individuals produce antibodies directed against one of their own erythrocyte membrane antigens. The hemolysis in autoimmune hemolytic anemia is most commonly extravascular rather than intravascular, and the liver and spleen play a major role in the clearance of the antibody-coated cells. The importance of complement in the destruction of IgM-coated cells has also been recognized.

Direct Coombs antiglobulin reactions in Gambian children with Plasmodium falciparum malaria. II. Specificity of erythrocyte-bound IgG

The cause of direct Coombs (DAT) positivity in West African (Gambian) children has been investigated. Results obtained from a comparison of two groups of primary school children, one from an area hyperendemic for P. falciparum malaria and the other partially protected from malaria, indicate an association between a high incidence of DAT positivity and P. falciparum parasitaemia with raised serum antibody titres to falciparum schizonts. Erythrocytes taken from children with a high IgG DAT titre were subjected to acid elution and the eluates examined for IgG content and antigen specificity. Eluted IgG had specific antibody activity against P. falciparum schizont antigen as demonstrated by means of the indirect fluorescent antibody technique. Cross-reaction was not observed with either P. falciparum gametocytes or P. malariae schizonts. No blood group specificity could be demonstrated in either the red cell eluates or serum taken from children with DAT positive red cells. The results provide convincing evidence which implicates falciparum malaria in the aetiology of Coombs positivity in Gambian children. It is probable that erythrocyte sensitization results from passive attachment of circulating complement-fixing malaria antigen-antibody complexes.

The role of complement in the clearance of cold agglutinin-sensitized erythrocytes in man

To define the pathophysiologic mechanisms of cold agglutinin disease, we investigated a human model of this syndrome in normal volunteers and in patients with diminished levels of serum complement. Subjects received intravenous injections of autologous, chromated (51Cr) erythrocytes which had been exposed in vitro to purified cold agglutinin preparations and to fresh autologous serum (as a source of complement). In vitro tests confirmed that such cells were coated with activated complement components (C3b), but not with immunoglobulin. Studies of erythrocyte clearance and simultaneous organ scanning showed that erythrocytes sensitized with low levels of cold agglutinin primarily undergo reticuloendothelial sequestration by the liver rather than intravascular hemolysis. After the initial sequestration of C3b-coated erythrocytes, a fraction of the cells are released back into the circulation and survive normally thereafter. Both phenomena are dose dependent and closely follow the sequestration and release pattern observed with IgM isoagglutinin sensitization. Experiments that used heated autologous serum as a source of B3 inactivator demonstrated that functionally intact C3b is required for hepatic sequestration. Erythrocytes coated with C3d were not cleared from the circulation. In vitro assays that sued human macrophage monolayers suggested that the intrahepatic conversion of C3b to C3d is responsible for the release of sensitized erythrocytes back into the circulation. The clearance of cold agglutinin-sensititzed erythrocytes was compared to the clearance mediated by IgM isoagglutinin. We found that the rate of complement fixation by an IgM antibody proceeds rapidly in vivo that the time for complement activation is not a factor in limiting the rate of hepatic sequestration. The major limiting factor appears to be the rate of liver blood flow. Maximal in vitro coating of erythrocytes with C3d conferred protection from further cold agglutinin sensitization but not from IgM isoagglutinin-mediated clearance. This suggests a mechanism for the resistance to lysis observed in cells obtained from patients with the cold agglutinin syndrome and confirms the marked dependence of the site of C3 attachment on the site of membrane localization of the sensitizing antibody.

Identification of a C4 Subcomponent on C3d-coated erythrocytes

Test erythrocytes (E) used to evaluate anti-complement (C') antiglobulin sera have not been adequately standardized. This report describes a previously unrecognized C4-derived antigen (temporarily called X-Ag) found on E generally believed to be coated only with the C3d subcomponent of C3, X-Ag occurred on all E coated in vitro with C' by low ionic strength-sucrose or cold agglutinin methods and on E from ten of ten patients whose cells had been C' coated in vivo. It was not removed by incubating these cells with trypsin or fresh compatible serum. This antigen was found on "C4-only-coated" red blood cells made with normal or congenitally C2-deficient serum but not on cells similarly prepared with congenitally C4-deficient serum. It was not identified on E coated with C' via the alternate pathway, normal trypsinized cells, nor cells coated only with IgG. Absorption experiments utilizing purified complement components and subcomponents and G200 Sephadex fractions of normal human serum strongly suggest that X-Ag is a subcomponent of C4(C4d). These results show that at least one C' subcomponent other than C3d occures on both in vitro and in vivo C3d-coated erythrocytes and must be taken into account when such cells are used to evaluate antiglobulin reagents.

Prophylactic administrations of aspirin for the prevention of thrombo-embolic complications in postoperative reactive thrombocytosis

Hyperfunctioning platelets in the thrombocytotic patients after major surgery were satisfactorily controlled by a small dose of aspirin ingestion. Since aspirin is well documented as a potent inhibitor of platelet aggregation, a small dose of prophylactic administration of aspirin appeared to be a legitimate approach to a possible life-threatening thrombo-embolic complication after surgery, particularly when the platelets are excessively produced and hyperfunctioning.

Studies on the in vivo effects of antibody. Interaction of IgM antibody and complement in the immune clearance and destruction of erythrocytes in man

Purified human IgM isoagglutinins were utilized to sensitize (51)Cr-labeled erythrocytes so as to produce a known number of complement-fixing sites. These cells were then reinfused into the erythrocyte donor. A minimum of 20 C1-fixing sites/erythrocyte were required for decreased survival. As the amount of antibody coating the erythrocytes was increased, a larger percentage was sequestered. With 80 C1-fixing sites, more than 75% of the injected erythrocytes were removed from the circulation within 10 min. In each case, the clearance pattern consisted of rapid hepatic sequestration followed by a gradual return of a portion of the erythrocytes into the circulation where they survived normally. Clearance was shown to be dependent upon activation of the classical complement pathway, since sensitized cells survived normally in hereditary angioedema patients with low levels of C4 and no detectable C2. Exposure of sensitized cells to fresh serum for 15 min led to the deposition of 550-800 C3 molecules/C1-fixing site. Such cells were immune adherence positive, were agglutinated by anti-C3b, formed rosettes with human alveolar macrophages, and were sequestered in vivo, presumably because of the interaction of cell-bound C3b with the C3b receptor on hepatic macrophages. After exposure to heated serum as a source of the C3b inactivator, the cells were immune adherence negative, were agglutinated only by anti-C3d, did not form rosettes with macrophages, and survived normally in vivo despite, being Coombs positive. Cleavage of cell-bound C3b to C3d may explain the release phase of the IgM clearance pattern. Whereas erythrocytes coated with IgM antibody and complement were previously thought to be sequestered in the liver because of extensive membrane damage, these experiments suggest that clearance is determined by the interaction of erythrocyte-bound complement fragments with specific receptors on hepatic macrophages.

Mechanisms of immune lysis of the red cells in hereditary erythroblastic multinuclearity with a positive acidified serum test and paroxysmal nocturnal hemoglobinuria

The red cells of patients with hereditary erythroblastic multinuclearity with a positive acidified serum test (HEMPAS), a form of congenital dyserythropoietic anemia, and the cells of patients with paroxysmal nocturnal hemoglobinuria (PNH) are lysed more readily than normal cells by certain antibodies, notably cold agglutinins (anti-I) and complement. With some but not other examples of anti-I, HEMPAS and PNH cells adsorbed more antibody than normal cells. Equal quantities of adsorbed antibody bound equal quantities of the first component of complement (C1) to normal, PNH, and HEMPAS cells. However, for a given quantity of bound antibody and C1, much more of the fourth component of complement (C4) was bound to HEMPAS cells than to normal cells. This resulted in the binding of proportionately larger quantities of the third component of complement (C3) to these cells. The same amount of bound C3 was found on the membranes of normal and HEMPAS cells for a given degree of lysis. Hence, the marked increase in lysis of HEMPAS cells is due to the increased adsorption of antibody and/or increased binding of C4.PNH cells bound the same amount of C4 per bound C1 as normal cells but bound more C3 than normal cells. However, the mean concentration of C3 on the membrane of PNH cells was one-third to one-fifth that on normal cells for a given degree of lysis. Hence, the increased lysis of PNH cells is due to the increased binding of C3 and increased hemolytic effectiveness of the bound C3.

Measurement of the third component of complement bound to red blood cells in patients with the cold agglutinin syndrome

The amount of the third component of complement (C3) bound to red cells of patients with the cold agglutinin syndrome was determined by a quantitative assay, measuring the fixation of the first component of complement by anti-C3. Abrupt reduction in the serum concentration of cold agglutinin by plasmapheresis markedly decreased the hemolytic rate, but the amount of C3 bound to circulating cells did not change appreciably. When this patient was transfused with normal cells. C3 accumulated on the transfused cells within 48 h to the level present on his own cells, but selective destruction of the transfused cells did not occur. When patients were subjected to acute cold stress, cell-bound C3 rose abruptly and intravascular hemolysis occurred. These studies suggest that most of the C3 detected on the circulating red cells of cold agglutinin patients is in an inactive form, and that the rate of attachment of C3 to the membrane is important in determining hemolysis.

Autoimmune haemolytic anaemias. V. studies on the resistance against complement haemolysis of the red cells of patients with chronic cold agglutinin disease

Experiments are described the results of which sustain the hypothesis that resistance against complement haemolysis, which is a characteristic of the red cells of patients with chronic cold agglutinin disease, is due to the following mechanism: when red cells react with cold auto-agglutinins in vivo, they are either haemolysed immediately, or, due to an unknown factor, escape direct haemolysis. In the latter case β₁E and β₁A disappear from the cell membrane. To the sites where these proteins have been attached once, no new β₁E or β₁A molecules can be bound. Full complement activation thus becomes impossible.

Role of antibody and complement in the immune clearance and destruction of erythrocytes. II. Molecular nature of IgG and IgM complement-fixing sites and effects of their interaction with serum

A model for the immune clearance and destruction of homologous erythrocytes has been further explored. In this model, every IgM anti-erythrocyte antibody molecule in an antibody preparation was shown to fix Cl. About 2000 IgG antibody molecules were required to form a Cl-fixing site on the guinea pig erythrocyte surface. 60 IgM complement-fixing sites per erythrocyte were required for the immune clearance of IgM-sensitized erythrocytes. This number of sites could be detected by a direct agglutination test. 1.4 complement-fixing sites were required for immune clearance of IgG-sensitized cells, a number of molecules which could not be detected by direct agglutination. This number could, however, be detected with the use of a Coombs antiglobulin reagent. Depletion of the late components of complement (C3-9) with cobra venom was associated with the loss of ability to clear IgM-sensitized cells and a marked deficit in the ability to clear IgG-coated cells. Thus, late (C3-9) components of complement as well as an early component (C4) were required for normal clearance of sensitized erythrocytes. There was no evidence that activation of the alternate pathway of complement action could lead to accelerated erythrocyte clearance. In vitro incubation of IgG and IgM-sensitized erythrocytes in fresh serum led to deposition of C3 and C4 on the erythrocyte surface. IgM-sensitized cells treated in this way had a normal survival. IgM-sensitized cells also were shown to remain Coombs positive after their release from the liver. The evidence suggests that the interaction of an IgM site with fresh serum in vitro and in vivo leads to formation of a site which allows for sequestration of cells in the liver. With continued exposure to serum components, this site is destroyed or inactivated. This serum-dependent inactivation is complement-dependent as shown by the use of EDTA-treated and C4-deficient serum. IgG complement-fixing sites are only partially inactivated by incubation in fresh serum, further emphasizing the differences in the biologic activity of IgM and IgG antibodies.

Haemolytic anaemia in the rabbit following the injection of human anti-I cold agglutinins

Anti-I cold agglutinins, purified from the serum of patients with chronic cold haemagglutinin disease, were injected intravenously into adult rabbits, which are known to have I antigen on their red cells. This caused acute intravascular haemolysis, with haemoglobinaemia, haemoglobinuria and anaemia. In addition, there was an acute, but usually transient, thrombocytopenia and neutropenia. Anticoagulation with heparin or Arvin had no influence on the effects of cold agglutinin injection, but massive doses of heparin, thought to interfere with complement binding by the cold agglutinin, did prevent the haemolysis, thrombocytopenia and neutropenia. A rabbit, given daily injections of cold agglutinin, developed significant intravascular haemolysis only with the first injection. However, a chronic extravascular haemolytic anaemia occurred with marked spherocytosis, reticulocytosis and shortening of the red cell survival. The effects of injection of human anti-I cold agglutinins into rabbits are analogous to certain aspects of the human disease and this rabbit model may be useful in further studies of in-vivo complement binding and removal of complement coated cells.

Autoimmune haemolytic anaemias. 3. Preparation and examination of specific antisera against complement components and products, and their use in serological studies

The preparation and examination of agglutinating antisera, specific for β1E, β1A, α2D and the /β1C/ determinant of the β1C molecule are described. With these reagents it could be established that anticomplement serum does not contain antibodies against the B determinant of the β1C molecule, while antiserum prepared with β1C globulin does. Further, the complement factors present on red cells, the complement coating of which was effected in various ways, were studied.

Whereas red cells incubated in vitro with haemolytic iso- or auto-antibodies are agglutinated by anti-β1E, anti-β1A and anti-α2D sera, the cells of patients with autoimmune haemolytic anaemia of any of the serologically defined groups of this disease, only reacted with anti-α2D. The possible significance of these findings is discussed.

Chronic hemolytic anemia due to cold agglutinins. II. The role of C' in red cell destruction

The sera of four patients with chronic hemolytic anemia due to cold agglutinins deposited C' globulins on normal red cells at 37 degrees C. The circulating cells of the patients were heavily coated with C' complex and were relatively resistant to C' hemolysis by cold agglutinin. Such red cells were removed from the patients' circulation at an exponential rate with (51)Cr t((1/2)) that varied from 7 to 19 days. Normal red cells were removed rapidly by hepatic sequestration during the first hours in the patients' circulation. Thereafter, a slower rate of abnormal destruction occurred which was associated with the accumulation of C' complexes on the red cell and the development of resistance to C' hemolysis by cold agglutinin. Normal red cells coated with sufficient C' complex by action of cold agglutinins in vitro to produce resistance to C' hemolysis by cold agglutinins demonstrated varying degrees of improved survival during the first hours in the circulation of three of the patients. The levels of serum C' were reduced in all four patients with chronic hemolytic anemia due to cold agglutinins. Transfusion of large volumes of normal red cells into two patients further reduced serum C'. (51)Cr-labeled normal red cells survived longer after red cell transfusions than before, because of less rapid destruction during the first hours in the circulation. The reduction in serum C' levels appeared responsible for the improved survival. In subjects without cold agglutinins, the presence of the spleen decreased the survival of red cells from a patient who had previously undergone splenectomy. Splenic removal also predominated in the reduced survival of autologous red cells in one patient. Neither hepatic nor splenic mechanisms predominated in removing autologous C'-coated cells in the other two patients.