QUANTITATIVE STUDIES OF THE EFFECT OF RED-BLOOD-CELL SENSITIZATION ON IN VIVO HEMOLYSIS

Haemoglobin levels in autoimmune haemolytic anaemias at diagnosis: relationship with immunoproteins on red blood cells

Previous investigations of the relationship between characteristics of immunoproteins on red blood cells (RBCs) and the occurrence of autoimmune haemolysis yielded divergent results. Here, we studied these characteristics in autoimmune haemolytic anaemias (AIHAs) to determine their relationship with the degree of anaemia at diagnosis. We studied at diagnosis 52 cases of warm AIHA with positive direct antiglobulin test. Immunohaematological testing and determination of immunoglobulin class, complement, and immunoglobulin G (IgG) were performed using gel technology (GCT). Median haemoglobin (Hb) levels significantly differed between cases with IgG1 only or negative for IgG subclasses (7.4 g/dl), those with IgG3 or IgG1 + IgG3 (6.5 g/dl), and those with multiple immunoglobulins (5 g/dl). Logistic regression indicated that IgG3 detection was the only variable significantly related to the occurrence of RBC transfusion in AIHA (odds ratio 4.05, 95 % CI 1.1-14.7). In our study, the type of immunoprotein(s) on the RBC surface was associated with different Hb levels at AIHA diagnosis. IgG3 and multiple immunoglobulins were associated with lower Hb levels; IgG3 was also associated with a higher percentage of patient transfusions in the first week after diagnosis. Thus, qualitative differences in these immunoproteins may lead to deeper and more prolonged anaemia levels, influencing the need for RBC transfusion.

Autoimmune hemolytic anemia with gel-based immunohematology tests

We used gel centrifugation tests (GCTs) to analyze the relationship between the diagnosis and immunohematology tests used for autoimmune hemolytic anemia (AIHA). The study included 588 samples positive for the direct antiglobulin test (DAT). Of these, 52 were from patients diagnosed with AIHA. Immunoglobulin (Ig) class, IgG1, IgG3, and complement were measured. DAT strength had the strongest correlation with AIHA diagnosis (odds ratio [OR], 23), followed by anti-IgG titer 300 (OR, 8.4), anti-IgG titer 1,000 (OR, 10.5), and C3d agglutination strength (OR, 1.7). Decision tree analysis revealed that DAT strength and anti-IgG titer higher than 100 were the best predictors of AIHA. Multidimensional scanning analysis found a high grade of similarity among DAT strength, anti-IgG titer, and IgG strength in the AIHA samples. This observation was not detected in DAT-positive samples from patients without AIHA. DAT strength remained the best diagnostic indicator for AIHA and had the strongest association with AIHA compared with other commercially available immunohematology tests. The other tests, despite good correlation with AIHA diagnosis, did not add useful information.

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.

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.

Flow cytometry: its applications to immunohaematology

Flow cytometry, using fluorescent probes, has only recently been applied to practical aspects of immunohaematology. It has been used for the detection and quantitation of cell-bound immunoglobulins and complement, minor cell populations, cellular antigens, and platelet and granulocyte antibodies. Practical applications of detecting minor cell populations have been successful in determining the extent of fetal maternal haemorrhage; determining the survival of transfused RBCs (small and large volumes); demonstrating RBC chimaerism (e.g. following bone marrow transplantation) and RBC mosaicism (e.g. demonstration of the McLeod phenotype carrier status). A large variety of cellular antigens have been demonstrated on RBCs, platelets and white cells using flow cytometry. Quantitation of RBC antigens by flow cytometry has been found to be much more objective and accurate than the routinely used serological approaches for establishing zygosity in paternity studies. Flow cytometry has been found to be a sensitive, objective and reproducible method for detecting platelet auto-and alloantibodies, and has also been used to detect granulocyte antibodies. More recently, it has been used to detect antibodies to monocytes and lymphocytes. As flow cytometers become more commonly available, many of these applications may become routine in clinical pathology laboratories.

An autoantibody with activity dependent on red cell age in the serum of a patient with autoimmune haemolytic anaemia and a negative direct antiglobulin test

A red cell IgM autoantibody with anti-e specificity was identified in the serum of a rhesus-negative (rr) patient presenting with haemolytic anaemia and a negative direct antiglobulin test. The autoantibody strongly agglutinated normal allogeneic rhesus-negative (rr) red cells in saline at 37 degrees C but had only weak activity for autologous red cells. Incubation of the patient's serum with subpopulations of normal allogeneic red cells obtained by density fractionation, demonstrated that the strong agglutinating activity of the autoantibody was for red cells with density greater than 1.090 g/ml. Young red cell subpopulations of lower density gave weak reactions and low titration scores equivalent to those obtained with autologous red cells during the haemolytic episode. The patient's red cells during remission however, when the patient's haemoglobin level had returned to normal, were strongly agglutinated by serum samples taken during the haemolytic episode; as was the case with normal allogeneic red cells, the strong activity was for patient red cells with density greater than 1.090 g/ml, red cell populations of lower density giving low titration scores. The findings in this case indicate that the patient's red cells which had survived haemolysis during the haemolytic episode were young red cells (density less than 1.090 g/ml), the weak sensitization of these cells being insufficient to cause their destruction by macrophages. Furthermore, these findings, together with observations that IgG autoantibodies may also bind less strongly to young red cells [Gray et al., Br. J. Haemat., 55: 335-345, 1983; Branch et al., Blood 63: 177-180, 1984].(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of IgG anti-Rho(D) in adult patients with chronic autoimmune thrombocytopenia

Seventeen adult patients with chronic (15 cases) or acute (two cases) autoimmune thrombocytopenia (ITP) were given intravenous and/or intramuscular injections of 0.75-4.5 mg of IgG anti-Rho(D) over a period of 1-5 days. Significant elevations of the platelet count (increments greater than 50 X 10(9)/liter) resulted in 13 of 15 Rh-positive patients but not in either of two Rh-negative patients. Heat-aggregated human albumin given to one of the Rh-negative patients also did not lead to a significant increase of the platelet count. The elevation of the platelet counts in Rh-positive patients after IgG anti-Rho(D) administration was often transient (less than 4 weeks), but long-term benefit (greater than 5 months) was achieved in five cases. The IgG concentration on RBC from five Rh-positive patients studied increased from a usually undetectable value before to approximately 700-1,700 IgG molecules/per RBC after anti-Rho(D) administration resulting in a strongly positive direct antiglobulin test. Nevertheless, an overt clinical hemolysis was seen in only one patient. The clearance of autologous 51Cr-labeled RBC was determined in four patients and was slightly enhanced in three and normal in one splenectomized patient. We conclude that the Fc receptor blockade involved in platelet sequestration was not associated with the induction of significant RBC clearance and that a reversible interaction of sensitized RBC with phagocytic cells and/or a low-grade destruction of these cells might be sufficient for the elevation of circulating platelets in the majority of patients with ITP.

Antibodies reactive with surface membranes of cellular elements in the blood

Autoreactive antibodies or immune complexes may accelerate clearance of mature erythrocytes, leukocytes, and platelets from the circulation in patients with rheumatologic and immunologic disorders. The most compelling evidence for immune injury to hematopoietic cells exists in patients with systemic lupus erythematosus and patients with Felty's syndrome and its variants. These disorders may also cause tissue inflammation, which in turn commonly results in underproduction of erythrocytes and development of thrombocytosis. However, recent evidence indicates that underproduction of hematopoietic cells may also result from immune injury to cellular elements in the bone marrow. In many laboratories, sensitive techniques are now clinically available for the detection of cell-associated immunoglobulin and complement. These assays have helped confirm the role of antibody in the pathogenesis of autoimmune hemolytic anemia and idiopathic thrombocytopenic purpura. However, recent data indicate that there is probably a continuum between the amount of immunoglobulin and complement found on normal cells and that found in a variety of disease states. In several of these disorders, additional evidence will be required to establish that the increase in cell-bound immunoglobulin leads to a decrease in the life-span of the cell. In order to provide significant help to the clinician managing an individual patient, these serologic tests must be capable of identifying the portion of the cell-associated protein actually involved in the destructive process. The availability of monoclonal reagents capable of identifying restricted regions on cell-bound immunoglobulin may help identify molecules bound specifically as antibody and may help identify the antigens involved in autoimmune disorders.

Destruction of IgG-sensitized erythrocytes by human blood monocytes: modulation of inhibition by IgG

The in vitro interaction between monocytes and erythrocytes sensitized with non-complement binding IgG antibodies (i.e. the Rh antibody anti-D:EAIgG anti-D) is completely inhibited by low concentrations of IgG (E.G. 30--100 microgram/ml). However, the interaction between monocytes and erythrocytes sensitized with IgG anti-A (EAIgG anti-A) is not inhibited by IgG. The findings presented in this paper indicate that this difference is probably due to the difference in the number of IgG antibody molecules per EAIgG. Thus, the higher the number of IgG antibody molecules per EAIgG, the less the interaction between EAIgG and monocytes is inhibited by IgG. A second factor which proved to have a strong influence on inhibition by IgG was the number of EAIgG per monocyte. When the number of EAIgG per monocyte was increased from 1 to 32, the percentage of inhibition by a fixed amount of IgG (50 microgram/ml) decreased significantly. This in vitro effect is only evident when relatively weakly sensitized erythrocytes are used and, in vivo, destruction of these weakly sensitized red cells (e.g. EAIgG anti-D) is confined to the spleen. Since a considerable haemoconcentration occurs in this organ, it is conceivable that a high EAIgG:macrophage ratio is accomplished. The latter data are an indication that this high ratio may allow interaction between weakly sensitized erythrocytes and splenic macrophages despite the presence, in vivo, of a high concentration of IgG, and that, in this way, in the spleen, the inhibitory effect of IgG is overcome.

Ultrastructural mapping of methyldopa and anti-D IgG erythrocyte antigen receptors

The ultrastructural distribution pattern and site density of alpha-methyldopa immunoglobin G (alpha-MD IgG) on the red cell membrane was observed and compared with that of anti-D IgG, with ferritin-conjugated rabbit anti-human IgG and [125I]anti-D. alpha-MD IgG binds to all common types of human red cells, both Rho (D) positive and negative, to give a random, aperiodic distribution pattern grossly indistinguishable from the red cell D receptor site pattern. alpha-MD IgG inhibits the binding of [125I]anti-D to D-positive red cells when the reaction is controlled with respect to total reaction volume, ionic strength, and the appropriate concentrations of the two IgG reactants. To determine if a alpha-MD IgG binds to the D-antigen receptor, D-positive red cells were sensitized with alpha-MD and [125I]anti-D IgG spearately and with both IgG preparations. The cell-bound radioactivity served to identify what proportion of the total ferritin-labeled IgG sites were due to anti-D. With nonsaturating concentrations of anti-D the number of IgG sites observed was equal to the sum of the sites found when the red cell was sensitized separately with alpha-MD and anti-D IgG. With saturating concentrations of anti-D there was a reduction in the expected number of IgG sites, indicating that alpha-MD IgG was excluded from binding. There was no comparable interaction of alpha-MD IgG and anti-D IgG when D-negative red cells were used. The results obtained indicate that alpha-MD IgG does not bind to the D antigen. The interaction between alpha-MD IgG and anti-D IgG for binding sites on the red cell membrane may be due to the close physical proximity of the two receptors, so as to produce steric hindrance in binding of the two IgG preparations when both are present. The alpha-MD IgG receptor appears to be a part of the Rh antigen complex that occurs in both D-positive and D-negative red cells and probably contains receptors for other types of warm-antibody immune hemolytic anemias.

Quantitative immunology of immune hemolytic anemia. I. The fixation of C1 by autoimmune antibody and heterologous anti-IgG antibody

The fixation of the first component of complement (C[unk]1) by rabbit and goat anti-IgG antibodies reacting with auto- or isoimmune antibodies attached to red cells has been investigated. Two molecules of the rabbit IgG anti-IgG were required to fix a single molecule of C[unk]1, whereas only one molecule of goat IgM anti-IgG was required. The relationship between the number of auto- or isoimmune antibody molecules attached to the red cells and the amount of C[unk]1 fixed by anti-IgG was determined by the concentration of anti-IgG. A concentration of anti-IgG was found such that the number of molecules of C[unk]1 fixed was directly proportional to the concentration of auto- or isoimmune antibody. By this method a sensitive, reproducible minimum estimate of the amount of cell-bound and serum antibody could be made.

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

The red cells of patients with chronic hemolytic anemia due to cold agglutinins are agglutinated by antiglobulin serum in a nongamma reaction due to the coating of beta-globulins, C'4 and C'3. The red cells of such patients are abnormally resistant to C' hemolysis by cold agglutinin. Normal red cells can be made equally resistant to C' hemolysis by incubation with cold agglutinin and normal serum at temperatures which allow transient reactions between the red cells and cold agglutinins. The development of resistance to C' hemolysis was related to increasing susceptibility to agglutination in anti-beta(1c)- and anti-beta(1e)-sera and by increasing uptake of (131)I activity from labeled anti-beta-globulin serum containing antibodies for both globulins. There was decrease in the adsorption of (131)I-labeled cold agglutinin during the development of resistance to C' hemolysis and reduced susceptibility to agglutination by cold agglutinins. Since cold agglutinins have been demonstrated to dissociate from the red cell, leaving fractions of C' globulin attached, it is postulated that repeated transient reactions produce the accumulation of incomplete C' complexes. Steric hindrance by the adsorbed C' complexes is probably responsible for the inhibition of the reaction with cold agglutinin. There is evidence that the adsorbed C' complexes also interfere with the hemolytic action of C' even when cold agglutinin has become reattached to the red cells. The accumulation of C' complexes by cold agglutinins appears to be the most important factor in the abnormal resistance to C' hemolysis exhibited by the patient's red cells. Other factors, such as the heterogeneity within a population of normal cells, appear to be of minor significance.